ArticlePDF AvailableLiterature Review

Abstract

Tree nuts are one of the most common foods causing acute allergic reactions and nearly all tree nuts have been associated with fatal allergic reactions. Despite their clinical importance, tree nut allergy epidemiology remains understudied and the prevalence of tree nut allergy in different regions of the world has not yet been well characterised. We aimed to systematically review the population prevalence of tree nut allergy in children and adults. We searched three electronic databases (OVID MEDLINE, EMBASE and PubMed) from January 1996 to December 2014. Eligible studies were categorised by age, region and method of assessment of tree nut allergy. Of the 36 studies identified most were in children (n = 24) and from Europe (n = 18), UK (n = 8) or USA (n = 5). Challenge-confirmed IgE-mediated tree nut allergy prevalence was less than 2 % (although only seven studies used this gold standard) while probable tree nut allergy prevalence ranged from 0.05 to 4.9 %. Prevalence estimates that included oral allergy syndrome (OAS) reactions to tree nut were significantly higher (8-11.4 %) and were predominantly from Europe. Prevalence of individual tree nut allergies varied significantly by region with hazelnut the most common tree nut allergy in Europe, walnut and cashew in the USA and Brazil nut, almond and walnut most commonly reported in the UK. Monitoring time trends of tree nut allergy prevalence (both overall and by individual nuts) as well as the prevalence of OAS should be considered given the context of the overall recent rise in IgE-mediated food allergy prevalence in the developed world.
FOOD ALLERGY (T GREEN, SECTION EDITOR)
The Prevalence of Tree Nut Allergy: A Systematic Review
Vicki McWilliam
1,2,4
&Jennifer Koplin
1,3
&Caroline Lodge
3
&Mimi Tang
1,2,4
&
Shyamali Dharmage
1,3
&Katrina Allen
1,2,4,5
Published online: 2 August 2015
#Springer Science+Business Media New York 2015
Abstract Tree nuts are one of the most common foods causing
acute allergic reactions and nearly all tree nuts have been asso-
ciated with fatal allergic reactions. Despite their clinical impor-
tance, tree nut allergy epidemiology remains understudied and
the prevalence of tree nut allergy in different regions of the
world has not yet been well characterised. We aimed to system-
atically review the population prevalence of tree nut allergy in
children and adults. We searched three electronic databases
(OVID MEDLINE, EMBASE and PubMed) from January
1996 to December 2014. Eligible studies were categorised by
age, region and method of assessment of tree nut allergy. Of the
36 studies identified most were in children (n=24) and from
Europe (n=18), UK (n=8)orUSA(n=5). Challenge-
confirmed IgE-mediated tree nut allergy prevalence was less
than 2 % (although only seven studies used this gold standard)
while probable tree nut allergy prevalence ranged from 0.05 to
4.9 %. Prevalence estimates that included oral allergy syn-
drome (OAS) reactions to tree nut were significantly higher
(811.4 %) and were predominantly from Europe. Prevalence
of individual tree nut allergies varied significantly by region
with hazelnut the most common tree nut allergy in Europe,
walnut and cashew in the USA and Brazil nut, almond and
walnut most commonly reported in the UK. Monitoring time
trends of tree nut allergy prevalence (both overall and by indi-
vidual nuts) as well as the prevalence of OAS should be con-
sidered given the context of the overall recent rise in IgE-
mediated food allergy prevalence in the developed world.
Keywords Tree nut allergy .Systematic review .Prevalence .
Epidemiology
Abbreviations
Primary tree
nut allergy
IgE-mediated allergic reaction upon exposure
to tree nuts that is due to a specific immune
response directed against tree nut allergens
Secondary
tree nut
allergy
IgE-mediated allergic reaction upon exposure
to tree nuts that is due to cross-reactivity of
specific IgE directed against non-tree nut
allergens
Tree nut
sensitisation
Presence of tree nut allergen-specific IgE
measured by skin prick test (SPT) or specific
IgE blood testing (sIgE)
Oral allergy
syndrome
(OAS)
A secondary tree nut allergy that occurs pre-
dominantly in pollen-sensitised individuals,
mediated by cross-reactive IgE responses to
allergens present in pollen and other plants.
Presents with oral pharyngeal symptoms
(itching mouth/tongue)
Pollen food
syndrome
(PFS)
Another term for oral allergy syndrome
This article is part of the Topical Collection on Food Allergy
*Katrina Allen
katie.allen@rch.org.au
1
Murdoch Childrens Research Institute, Royal ChildrensHospital,
Flemington Rd, Parkville 3052, Victoria, Australia
2
Department of Paediatrics, University of Melbourne,
Parkville, Australia
3
Allergy and Lung Health Unit, Centre for Epidemiology and
Biostatistics, The University of Melbourne, Melbourne, Australia
4
Department of Allergy and Immunology, The Royal Childrens
Hospital, Flemington Road, Parkville, Australia
5
Institute of Inflammation and Repair, University of Manchester,
Manchester, UK
Curr Allergy Asthma Rep (2015) 15: 54
DOI 10.1007/s11882-015-0555-8
Introduction
Tree nut is the collective term used to describe nuts that grow
on trees. Contrary to popular belief, peanuts are not tree nuts
and are in fact a groundnut and classified as a legume. Tree
nuts most likely to result in an IgE-mediated food allergy
reaction are almond, brazil nut, cashew nut, hazelnut,
macadamia, pecan, pistachio and walnut. Although botanical-
ly unrelated, tree nut and peanut allergies share many clinical
similarities. Peanut and tree nuts are two of the most common
foods reported to cause IgE-mediated food allergic reactions.
IgE-mediated food allergy reactions can occur after ingestion
of very small amounts of peanut and tree nut, typically within
minutes of ingestion with symptoms including hives, angio-
edema or vomiting. Reactions can also be life threatening,
with the most severe reactions termed anaphylaxis. Peanut
and tree nuts together account for 7090 % of reported food-
induced anaphylaxis fatalities, with tree nuts alone accounting
for around 1840 % [14]. Allergies to peanut and tree nuts
also commonly co-exist with around 2030 % of people with
a peanut allergy also allergic to one or more tree nuts [5,6].
For individuals with one tree nut allergy, around 30 % will
have at least one additional tree nut allergy [6]. Tree nut and
peanut allergies are usually lifelong [7]. Peanut allergy has
been well described and widely reported with population
prevalence estimates between 1 and 6 % [8,9]. Despite the
similarities to peanut allergy, the population prevalence of tree
nut allergy has been less well characterised.
Determining tree nut allergy prevalence at a population
level can be complex. Firstly, the definition of a tree nut
may vary. Some studies include peanut and tree nuts together
as nuts, while other studies only include one or two tree nuts.
Few studies investigate allergy to all eight common individual
tree nuts. Secondly, allergic reactions to tree nuts can result
from primary IgE-mediated mechanisms or, alternatively, via
secondary cross-reactivity mechanisms to birch pollen, in a
form of food allergy known as oral allergy syndrome (OAS)
or pollen food syndrome (PFS). In individuals with birch pol-
len sensitisation, birch pollen-specific IgE can cross-react with
similar proteins found in a range of fresh fruits, vegetables and
nuts (apple, apricot, carrot, celery, hazelnut, peach, peanut,
pear, potato and plum) resulting in oral pharyngeal symptoms
[10,11]. Finally, the method of tree nut allergy diagnosis may
vary from self-reported methods such as surveys and question-
naires (which have been found to overestimate the true prev-
alence of food allergy) [8,9], IgE testing methods such as
skin prick testing (SPT) or specific IgE (which are limited to
IgE-mediated food allergy and are indicative of sensitisation
not clinical allergy), to the most objective but time-consuming
and cumbersome methods of oral food challenge (OFC) and
double-blind placebo-controlled food challenges (DBPCFC).
One previous systematic review by Zuidmeer et al., of
studies published between 1990 and 2006, reported the
prevalence of perceived reactions to tree nut as ranging be-
tween 0 and 7.3 %; however, most studies included in this
review (n=27 of 36) were based in Europe where the preva-
lence of oral allergy syndrome is high, and few studies used
objective definitions of tree nut allergy such as challenge con-
firmed outcomes [12]. A more recent systematic review by
Nwaru et al. was confined to European studies only and did
not distinguish between individual tree nuts [13]. A more up-
to-date global prevalence estimate of tree nut allergy is needed
since 20 new studies have been published since 2006, and
understanding the regional variation in tree nut allergy is im-
portant given the overall rising burden of food allergy [14,15]
in developed countries and the importance of tree nuts as a
cause of severe allergic reactions.
The aim of this paper is to provide a comprehensive, up to-
date systematic review of the population prevalence of tree nut
allergy in children and adults including details of all individual
tree nuts in various regions of the world.
Methods
Search Strategy
Following closely the methods and procedures of the Pre-
ferred Reporting Items for Systematic Reviews and Meta-
analyses (PRISMA) guidelines [16], we systematically
searched three electronic databases (OVID MEDLINE,
EMBASE and PubMed) based on a search strategy formulat-
ed with the assistance of a research librarian. The search strat-
egy was created in OVID MEDLINE and modified for
EMBASE and PubMed. Figure 1outlines the full OVID
MEDLINE search strategy.
Study Selection
Tree nuts were defined as walnut, almond, pistachio, cashew,
pecan, hazelnut, macadamia and Brazil nut. Studies reporting
on all forms of allergic reactions (primary and secondary IgE-
mediated and non-IgE-mediated reactions) were included and
there were no age restrictions applied. All tree nut allergy
outcomes were included for both individual and combined
tree nut allergies. We included eligible studies that reported
tree nut allergy based on self-report, sensitisation (sIgE or
SPT), OFC/DBPCFC or convincing clinical history. The
search was limited to English-language articles and, to capture
more recent publications, limited to the period January 1996
to December 2014. To ensure unbiased estimates of tree nut
allergy prevalence in the community, we excluded studies in
selected patient groups or those performed in hospital or aller-
gy clinic settings and included only population-based cross-
sectional and cohort studies. Reviews and case reports were
54 Page 2 of 13 Curr Allergy Asthma Rep (2015) 15: 54
excluded along with studies of which full-text articles were
not available.
Identified articles were screened via title and abstract by
two independent reviewers. Any discrepancies were resolved
by consensus and if necessary a third reviewer consulted. Ref-
erence lists of identified studies were reviewed for additional
articles. A full-text review was then undertaken for all articles
identified.
Quality assessment of the studies was performed by two
reviewers based on participation rate, ability of the study de-
sign to address tree nut allergy outcomes objectively and in-
clusion of individual tree nut information.
Analysis
Using a standardised method, relevant study details were
summarised including reference details, age, sample size
and response rate, prevalence estimates and 95 % confi-
dence intervals (CI) for all reported food allergy out-
comes (self-/parent report, specific IgE testing, skin prick
testing, symptoms and food challenges) for overall food
allergy and tree nut allergy. If not reported, prevalence
estimates were calculated as the observed proportion
with 95 % CI calculated on the assumption of a binomial
sampling distribution.
* The primary search was conducted in OVID MEDLINE and modified for EMBASE and PubMed. The
search involved a combinaon of three search groups as either MeSH terms or keywords, each of
which had to be present in order for an arcle to be included: 1) “nut s”, “tree nuts” or an individual
tree nut term; 2) “hypersensivity” or “allergy”; and 3) “prevalence” or “epidemiology”. The search
was limited to English language arcles. The exact search conducted in OVID MEDLINE is shown in the
box below.
1. (hazelnut* or hazel nut* or cashew*or pistachio* or almond* or treenut* or tree nut* or pecan* or brazilnut* or brazil nut*
or walnut*).af. 2. Nuts/ae, im, po, to 3. prevalence 4. Epidemiology 5. food hypersensitivity/ or nut hypersensitivity 6.
allerg*.af. 7. (1 or 2) and (3 or 4) and (5 or 6) 8. nut hypersensitivity/ep 9. food hypersensitivity/ep and (1 or 2) 10. 7 or 8 or
9 11. limit 10 to english language
Addional records idenfied
n= 10
Records aer duplicates removed
n= 333
Records screened (tle/ abstract)
n=333
Full text arcles excluded n= 46
Selected populaon = 26, Treenut allergy prevalence not
reported =7, Review arcle = 6,No Prevalence data = 7
Full text-arcles assessed for
eligibility
n=82
Records Excluded
n=261
Total
n=36
PubMed (Jan 2013-Dec 2014)
n=11
Embase(Jan 1996-Dec 2014)
n=230
Fig. 1 Summary of the search method
Curr Allergy Asthma Rep (2015) 15: 54 Page 3 of 13 54
We subclassified the prevalence estimates and 95 % CI for
age, region and method of tree nut allergy diagnosis.
For this review, the approaches used to determine tree nut
allergy have been grouped as follows:
1. Confirmed tree nut allergydefined as food challenge
confirmed tree nut allergy (OFC or DBPCFC) or recent
history (<2 years) of IgE-mediated reaction with positive
allergy testing (SPT or sIgE) undertaken as part of the
study in the absence of a formal food challenge.
2. Probable tree nut allergydefined as reported history
(>2 years) of IgE-mediated reaction with allergy or self-
report of doctor diagnosis (presumed to include allergy-
specific history and testing).
3. Self-reported tree nut allergydefined as parent or self-
reported tree nut allergy in the absence of data on allergy
testing.
4. Sensitisation only (allergy testing via SPT or sIgE, with-
out confirmation of clinical allergy).
We performed a random effects meta-analysis and in an
attempt to address the significant heterogeneity observed
across the studies stratified by age, region and method of tree
nut allergy diagnosis. Statistical analyses were undertaken
using STATA 13 (Stata Corp, College Station, TX, USA).
Results
Study Selection and Characteristics
Figure 1summarises the search methodology. The systematic
search of the literature resulted in 333 articles after duplicates
were removed. Title and abstract review identified 261 that
did not meet the inclusion criteria. The remaining 72 articles
and an additional ten records identified through manually
searching reference lists underwent full-text review. Forty
six full-text articles were excluded (26 were in selected popu-
lations, seven did not report tree nut allergy prevalence, seven
did not include prevalence data and six were review articles).
Included studies are described in Table 1(n=36).Twenty
six studies were designed to measure overall food allergy
prevalence and reported tree nut allergy as a study outcome,
seven were studies specifically aimed at investigating tree nut
allergy prevalence and three studies included tree nut allergy
prevalence data as part of an investigation of peanut allergy
prevalence or associated factors.
Quality assessment of the studies based on participation rate,
ability of the study design to address tree nut allergy outcomes
objectively and inclusion of individual tree nut information re-
sulted in 28 studies graded as moderate and eight poor. Three of
the studies were assessed as poor because they were not de-
signed to measure tree nut allergy prevalence but reported some
tree nut prevalence data, which we have included in this review.
The majority (n=28) of the studies were population-based cross-
sectional studies and the remaining eight were cohort studies.
Six studies did not provide participation rate details, ten studies
hadaparticipationrateabove80%,13between50and80%
and seven less than 50 %. One study by Greenhawt et al. in
American college students had a participation rate of only 3 %
and reported a very high overall self-reported food allergy prev-
alence of 54 % and a self-reported tree nut allergy prevalence of
9.16 % (95% CI 6.811.9) [24]. This study has been included in
the summary table, but the prevalence estimates not discussed as
part of the review since the participation rate was extremely low
and the study therefore not necessarily representative of the
population from which it was sampled.
The random effects meta-analysis showed heterogeneity to
be too great to report pooled results (I
2
>98 %, p=0.000 for all
analyses).
Tree Nut Allergy Prevalence by Age and Allergy Diagnosis
Method
The majority (n=24) of studies in this review were in children
and adolescents, four studies included both adults and chil-
dren, six studies adults only and two studies reported an over-
all tree nut allergy prevalence without age breakdown; in one
of these studies, participants were >15 years [23] and the
second <61 years of age [25].
Prevalence estimate ranges for all allergy definitions,
categorised by age, are outlined in Table 2. Seven studies used
the most objective assessment of oral food challenge (or convinc-
ing recent history of allergic reaction together with positive
allergen-specific IgE) with an overall prevalence range of 0
1.6 %. Nine studies combined self-reported food allergy with
additional objective assessment such as specific details regarding
doctor diagnosis or sensitisation details (sIgE/SPT) and were
classified as probable food allergy for this review. The overall
probable tree nut allergy prevalence range was 0.054.9 %, with
only one study reporting adult data. However, the majority of
prevalence estimates for tree nut allergy were based on self-
reported reactions (n=20 studies). The self-reported tree nut al-
lergy prevalence range was wider for adults (0.188.9 %) and
those studies including both adults and children (0.411.4 %)
than those studies including only children (03.8 %). Overall
self-reported tree nut allergy prevalence ranged from 0 to 11.4 %.
Three studies based tree nut allergy prevalence on sensiti-
sation alone (sIgE or SPT) without any clarification of pres-
ence of clinical allergy. One reported hazelnut sensitisation by
SPT in Russian children of 0.8 % (95 % CI 0.41.1) and
Finnish children of 6.3 % (95% CI 3.69.8) [52]. The second
study reported sensitisation based on SPT of 1.0 % in 7-year-
old children in the UK [40]. The third study in adults reported
sensitisation prevalence to hazelnut of 9.26 % and walnut
2.98 % (overall 12.2 % (95% CI 11.712.7)) [20]. This was
54 Page 4 of 13 Curr Allergy Asthma Rep (2015) 15: 54
Tab l e 1 Summary of the characteristics of studies in review: studies published January 1, 1996Dec 31, 2014 (alphabetical by author)
Reference Country Study design Allergy outcome Type of allergy NParticipation
rate (%)
Age Individual
tree nuts
described
Prevalence
measure
Overall prevalence
%(95 %CI)(N)
Study
grading
Ahn et al. 2012 [17] Korea Cross-
sectional
2. Probable (self-
report of Dr
diagnosis and sIgE)
Primary and
secondary
7882 97 613 years NA Point and
lifetime
0.05 % (0.010.13)
(4/7882)
Moderate
Bedolla-Barajas
et al. 2014 [18]
Mexico Cross-
sectional
1. Self-report Primary and
secondary
1126 NA 1850 years Yes Point 0.18 % (0.020.64)
(2/1126)
Poor
Ben-Shoshan et
al. 2010 [19]
Canada Cross-
sectional
1. Self-report
2. Probable (self-
report of Dr
diagnosis and sIgE)
Primary and
secondary
9667 34.6 All ages with
breakdown
NA Point Children 1.1.73
(1.162.3)
2.0.69 (0.40.97)
Adults: 1. 1.07
(0.841.30)
2. 0.35 (0.270.44)
Overall: 1. 1.22 %
(1.001.44)
(118/9667)
2. 0.68 %
(0.540.83)
Moderate
Burney et al.
2014 [20]
Multi
(Europe)
Cross-
sectional
4. Sensitisation
(sIgE)
Primary and
secondary
17,366 54.9 2054 years Yes Point 12.2 % (11.712.7)
(2121/17326)
Moderate
Caffarelli et al.
2011 [21]
Italy Cross-
sectional
1. Self-report Primary and
secondary
625 69 514 years Yes 0.32 % (0.041.2)
(2/625)
Moderate
DuToit et al.
2008 [22]
UK
Israel
Cross-
sectional
1. Self-report Primary 4148 (UK)
4672 (Israel)
80.2 (UK)
83.2 (Israel)
418 years NA Point UK 1.85 % (1.52.3)
(77/4148)
Israel 0.13 %
(0.050.3)
(6/4672)
Moderate
Emmett et al.
1999 [23]
UK Cross-
sectional
1. Self-report NA 16,434 NA All ages NA Point 0.40 % (0.300.51)
(63/16,434)
Moderate
Greenhawt et. al.
2009 [24]
USA Cross-
sectional
1. Self-report NA 571 3.5 >18 years NA Point 9.16 % (6.811.9)
(47/571)
Poor
Kanny et al.
2002 [25]
France Cross-
sectional
1. Self-report Primary and
secondary
16,174 52 All ages
<60
NA Point 3 % (2.73.20) Moderate
Kaya et al.
2013 [26]
Turkey Cross-
sectional
1. Self-report
3. Confirmed
(DBPCFC)
Primary 10,096 89.9 1115 years Yes Lifetime 1.1.2 % (0.11.4)
(121/10,096)
3.0.05 % (0.020.1)
(6/100,096)
Moderate
Kljakovic et al.
2009 [27]
Australia Cross-
sectional
1. Self-report NA 3851 85 45years No Lifetime 1.79%(1.42.3)
(69/3851)
Poor
Kristjansson
et al. 1999 [28]
Sweden
Iceland
Cross-
sectional
1. Self-report
3. Confirmed
(OFC)
NA 324
(Iceland)
328
(Sweden)
79 (Iceland)
90 (Sweden)
18 months No Point 1. Sweden 0.3 %
(0.01.6) (1/328)
Iceland 0 %
3.0 % for Iceland
and Sweden
Moderate
Curr Allergy Asthma Rep (2015) 15: 54 Page 5 of 13 54
Tab l e 1 (continued)
Reference Country Study design Allergy outcome Type of allergy NParticipation
rate (%)
Age Individual
tree nuts
described
Prevalence
measure
Overall prevalence
%(95 %CI)(N)
Study
grading
Leung et al. 2009
[29]
Hong Kong Cross-
sectional
1. Self-report
2. Probable (self-
report of Dr
diagnosis)
Primary and
secondary
3677 83.6 % 27 years NA NA 1. 0.41 (0.20.7)
(15/3677)
2. 0.3 % (0.20.5)
(11/3677)
Moderate
Marklund et al.
2004 [30]
Sweden Cross-
sectional
1. Self-report Primary and
secondary
1451 97 1321 years NA Point 11.37 % (9.512.8)
(165/1451)
Moderate
Mustafayev et al.
2012 [31]
Turkey Cross-
sectional
1. Self-report
2. Probable (detailed
history and SPT)
3. Confirmed (OFC)
Primary 6963 NA 1011 years Yes Point 1.3.5 % (3.1,3.9)
(223/6963)
2.4.9 % (4.4,5.4)
(341/6963)
3.0.05 % (0.03,0.15)
(4/6963)
Moderate
Nicolaou et al.
2010 [32]
UK Cohort 1. Self-report Primary 1029 94.9 8 years NA Lifetime 1.0 % (0.4,1.8)
(10/1029)
Poor
Orhan et al.
2009 [33]
Turkey Cross-
sectional
1. Self-report
2. Probable (SPT)
3. Confirmed (OFC)
Primary 2739 78.2 69 years Almond
and
walnut
Point 1.0.4 % (0.2,0.7)
(11/2739)
2.0.14 % (0.03,0.4)
(4/2739)
3.0 % (0,0.1) (0/2739)
Moderate
Ostblom et al.
2008 [34]
Sweden Cohort 1. Self-report Primary 2563 69 4 years NA Point 3.8 % (3.1,4.6)
(98/2563)
Moderate
Osterballe et al.
2009 [35]
Denmark Cohort 1. Self-report Specified primary
and secondary
843 77 22 years Yes Point 1. Primary 0 %
Secondary 8.9 %
(7.0,11.02)
(85/843)
Moderate
Penard-Morand
et al. 2005 [36]
France Cross-
sectional
1. Self-report Primary and
secondary
7781 81 911 years NA Lifetime 0.2 % (0.1,0.3)
(10/6672)
Moderate
Pereira et al.
2005 [37]
UK Cohort 1. Self-report Primary and
secondary
1532 48.7 11 and
15 years
NA Point 1.6 % (1.1,2.4)
(26/1532)
Poor
Pyrhonen et al.
2005 [38]
Finland Cross-
sectional
1. Self-report
2. Probable (self-
report of Dr
diagnosis)
Primary and
secondary
3308 69 14 years NA Lifetime 1.1.5 % (1.1,1.9)
(49/3308)
2.0.2 % (0.08,0.4)
(7/3308)
Moderate
Rance et al.
2005 [39]
France Cross-
sectional
1. Self-report Primary and
secondary
2716 77.6 214 years Yes Point 0.7 % (0.4,1.1)
(19/2716)
Moderate
Roberts et al.
2005 [40]
UK Cohort 4. Sensitisation
(SPT)
Sensitisation
only
5848 42 7 years Yes Point 1.04 % (0.8,1.3)
(61/5848)
Poor
Roehr et al.
2004 [41]
Germany Cross-
sectional
1. Self-report
2. Probable (SPT)
3. Confirmed (OFC)
Primary and
secondary
739 31.5 017 years Yes Point 1. NA
2. 2.7 % (1.6,4.1)
(20/739)
3. 1.4 % (0.7,2.5)
(10/739)
Moderate
54 Page 6 of 13 Curr Allergy Asthma Rep (2015) 15: 54
Tab l e 1 (continued)
Reference Country Study design Allergy outcome Type of allergy NParticipation
rate (%)
Age Individual
tree nuts
described
Prevalence
measure
Overall prevalence
%(95 %CI)(N)
Study
grading
Schafer et al.
2001 [42]
Germany Cross-
sectional
1. Self-report
SPT for hazelnut
only
Primary and
secondary
1537 60.7 2574 years NA Point 1.8.5 % (7.1,9.9)
(130/1537)
Moderate
Shek et al.
2010 [43]
Singapore
Philippines
Cross-
sectional
1. Self-report
2. Probable (self-
report of Dr
diagnosis)
Primary 25,692 74.2 46 years and
1416 years
NA Point 1.1.85 % (1.6,2.1)
(200/10775)
2.0.28 % (0.2,0.4)
(31/10,775)
Moderate
Sicherer et al.
1999 [44]
USA Cross-
sectional
1. Self-report Primary and
secondary
4374 62 All ages with
breakdown
Yes Point Children (<18 years)
0.2 % (0.05,0.4)
(5/2998)
Adults (>18 yrs)
0.7 % (0.5,0.9)
(59/8049)
Overall 0.5 %
(0.0,0.6)
(64/12032)
Moderate
Sicherer et al.
2003 [45]
USA Cross-
sectional
1. Self-report Primary and
secondary
13,493 52 All ages with
breakdown
Yes Point Children (<18 years)
0.2 % (0.1,0.4)
(7/3127)
Adults (>18 years)
0.1 % (0.4,0.6)
(50/9881)
Overall 0.4 %
(0.3,0.5)
(57/13,493)
Moderate
Sicherer et al.
2010 [46]
USA Cross-
sectional
1. Self-report Primary and
secondary
5300 42 All ages with
breakdown
Yes Point Children (<18 years)
1.1 % (0.05,0.4)
(31/2902)
Adults (>18 years)
0.5 % (0.4,0.6)
(53/9845)
Overall 0.6 %
(0.5,0.8)
(84/12,658)
Moderate
Tar iq et a l.
1996 [47]
UK Cohort 1. Self-report Some
participants had
SPT
Primary 1218 NA 4 years NA Point 0.1 % (0.02,0.6)
(2/1218)
Poor
Taylor-Black
et al. 2014 [48]
USA Cross-
sectional
1. Self-report Primary 368 43 412 years NA Point 1.82 % (1.06,2.9)
(17/932)
Poor
Venter et al.
2006 [49]
UK Cohort 1. Self-report
3. Confirmed (OFC)
Primary 798 55.4 6 years Yes Point 1. 1.37 % (0.8,2.5)
(11/798)
3. 0.25 % (0.03,0.9)
(2/798)
Moderate
Curr Allergy Asthma Rep (2015) 15: 54 Page 7 of 13 54
the highest reported prevalence estimate of all four methods of
tree nut allergy definition.
Tree Nut Allergy Prevalence by Region
Prevalence estimate ranges for each method of allergy defini-
tion are summarised by region in Table 3. Regional variation
in self-reported tree nut allergy prevalence is illustrated in
Fig. 2. Most studies were from Europe (n=18), the UK (n=
8), or the USA (n=5). There were three studies from Asia and
one each from Canada, Central America and Australia. Strat-
ifying by region highlighted a markedly higher prevalence of
tree nut allergy in some European countries with a range of
0.0411.4 %. OAS appeared to contribute to higher tree nut
allergy prevalence in some European countries since all three
of the studies reporting tree nut allergy prevalence over 8 %
were self-reported, all in adolescents and adults, and all from
Europe. Two of these studies directly reported that all tree nut
allergy found in their study was due to OAS [35,42] and the
third study did not specify the type of allergic reaction to tree
nuts, but overall 33 % of all allergy, to any food, was report-
edly due to OAS [30]. All other regions, regardless of allergy
definition, reported tree nut allergy prevalence less than 2 %.
Individual Tree Nut Allergy Prevalence
Tab le 4summarises the percentage of tree nut allergic partic-
ipants allergic to each individual tree nut by region. Fourteen
studies provided details of individual tree nut prevalence. The
prevalence of individual tree nut allergies varied by region.
Hazelnut was the most common tree nut allergy reported in six
of the seven studies from Europe accounting for 17100 % of
all tree nut allergies. The two studies from the USA reported
walnut and cashew as the most common tree nut allergies
ranging from 20 to 30 % and 1530 %, respectively. Brazil
nut allergy was reported commonly in the UK ranging from
24 to 33 %. The one study from Mexico reported low overall
tree nut allergy of 0.18 % (2/1126) with both participants
allergic to walnut. None of the studies reported on the preva-
lence of multiple tree nut allergies.
Tree Nut Allergy Prevalence Over Time
There is limited evidence to determine if the population
prevalence of tree nut allergy is increasing. Three studies
in the USA utilised random-digit telephone surveys in
1997, 2002 and 2008 [44,45,46]. Study design was
consistent across each sampling period and included a
large number of participants (n=4374; 13,493 and 5300,
respectively). No significant increase in adult self-reported
tree nut allergy prevalence was found over the three time
points. However, the prevalence of self-reported tree nut
allergy in children younger than 18 years had increased
Tab l e 1 (continued)
Reference Country Study design Allergy outcome Type of allergy NParticipation
rate (%)
Age Individual
tree nuts
described
Prevalence
measure
Overall prevalence
%(95 %CI)(N)
Study
grading
Venter et al
2008 [50]
UK Cohort 1. Self-report
3. Confirmed (OFC)
Primary 891 91.9 3 years Yes Point 3.0.93 % (0.34,2.0)
(6/642)
Moderate
Vierk et al .
2007 [51]
USA Cross-
sectional
1. Self-report
2. Probable (self-
report of Dr
diagnosis)
Primary 4482 NA >18 years NA Point 1.0.65 % (0.43,0.9)
(29/4477)
2.0.5 % (0.06,0.32)
(7/4477)
Moderate
Von Hertzen
et al. 2006
[52]
Finland
Russia
Cross-
sectional
4. Sensitisation
(SPT)
Primary and
secondary
Finland 367
Russia 446
NA 716 years Hazelnut
only
Point Finland 6.3 %
(3.6,9.8)
(17/271)
Russia 0.8 %
(0.2,2.4)
(3/356)
Moderate
54 Page 8 of 13 Curr Allergy Asthma Rep (2015) 15: 54
significantly (0.2 % in 1997, 0.5 % in 2002 and 1.1 % in
2008). Proportionally, the increase was greater than that
observed for peanut over the same time periods (0.4 % in
1997, 0.8 % in 2002 and 1.4 % in 2008).
Tabl e 2 Summary of the range of
prevalence estimates of tree nut
allergy in the reviewed studies
according to allergy assessment
method and age
Allergy definition and age Number
of studies
Range of prevalence
estimates (%)
References
Self-reported
Children 018 years
Adult
All ages
Overall
22
8
3
03.8
0.188.9
0.411.4
011.4
[21,22,2629,3134,3639,43,
44,45,46,4749,53]
[18,35,42,44,45,46,51,53]
[23,25,30]
Probable
Children 018 years
Adult
All ages
Overall
9
2
0
0.054.9
0.350.5
NA
0.054.9
[17,19,29,31,33,38,41,43,51]
[19,51]
Confirmed
Children 018 years
Adult
All ages
Overall
7
0
0
01.4
NA
NA
01.4
[26,28,31,33,41,49,50]
Sensitisation
Children 018 years
Adult
All ages
Overall
2
1
0
0.86.3
12.2
NA
0.812.2
[40,52]
[20]
Some studies are included in more than one category as they reported prevalence estimates obtained using more
than one allergy assessment method.
Tabl e 3 Summary of the range of reported prevalence estimates for tree nut allergy according to allergy assessment method and region
Region Self-report
Range %
(number of studies)
Probable
Range %
(number of studies)
Confirmed
Range %
(number of studies)
Sensitisation
Range %
(number of studies)
Asia Children
Adults
Overall
0.31.85 (3)
NA
0.31.85
0.050.3 (3)
NA
0.050.3
NA
NA
NA
NA
NA
NA
Europe Children
Adults
All ages
Overall
0.043.1 (10)
8.58.9 (2)
3.011.7
0.0411.7
0.24.9 (4)
1.6 (1)
NA
0.24.9
01.4 (6)
NA
NA
01.4
0.8 (1)
12.2 (1)
NA
0.812.2
UK Children
Adults
Overall
0.11.85 (5)
NA
0.11.85
NA
NA
0.250.93 (2)
NA
0.250.93
NA
NA
USA Children
Adults
Overall
0.21.82 (4)
0.50.7 (2)
0.21.82
NA
NA
NA
NA
NA
NA
Australia Children
Adults
Overall
1.79 (1)
NA
NA
NA
NA
NA
NA
NA
Canada Children
Adults
Overall
1.73 (1)
1.07 (1)
1.071.73
1.59 (1)
1.0 (1)
1.01.59
0.69 (1)
0.35 (1)
0.350.69
NA
NA
Central America Children
Adults
Overall
NA
0.02 (1)
NA
NA
NA
NA
NA
NA
Curr Allergy Asthma Rep (2015) 15: 54 Page 9 of 13 54
Fig. 2 Overall tree nut allergy
prevalence by region (%)
Tabl e 4 Percentage of tree nut allergics reporting reactions to the individual tree nuts by region
Region, study details (country) % of tree nut allergics reporting reactions to the individual tree nuts (number with specific tree nut
allergy/total number with any tree nut allergy)
Europe
Burney et al. 2014 [20] (multi-country)
Caffarelli et al. 2011 [21](Italy)
Mustafayev et al. 2012 [31](Turkey)
Kaya et al. 2013 [26](Turkey)
Osterballe et al. 2009 [35] (Denmark)
Rance et al. 2005 [39] (France)
Roehr et al. 2004 [41] (Germany)
Hazelnut 76 % (1605/2121), walnut 24 % (517/2121)
Hazelnut 100 % (2/2)
Hazelnut 42 % (104/243), walnut 34 % (83/243), pistachio 22 % (55/243)
Walnut 66 % (4/6), hazelnut 17 % (1/6), pistachio 17 % (1/6)
Hazelnut 75 % (56/75), Brazil nut 31 % (23/75), walnut 5 % (4/75), almond 3 % 2/75)
Hazelnut 53 % (10/19), walnut 32 % (6/19), almond 10 % (2/19), cashew 5 % (1/19)
Hazelnut 100 % (10/10)
USA
Sicherer et al. 1999 [44]
Sicherer et al. 2010 [46]
Walnut 37 % (24/65), cashew 12 % (5/65), Brazil nut 12 % (8/65), almond 11 % (7/65),
pecan 11 % (7/65), hazelnut 4.6 % (3/65), macadamia 3 % (2/65), unspecified 9 % (6/65)
Walnut 48 % (41/84), cashew 34 % (29/84), pecan 30 % (26/84), almond 29 % (25/84),
pistachio 22 % (19/84), Brazil nut 22 % (19/84), hazelnut 20 % (17/84),
macadamia 20 % (17/84), pine nut 13 % (11/84)
UK
Ve n t er et al . 2 0 0 8 [ 50]
Ve n t er et al . 2 0 0 6 [ 49]
Roberts et al. 2005 [40]
Tariq et al. 1996 [47]
Brazil nut 33 % (2/6), almond 33 % (2/6), hazelnut 17 % (1/6), cashew 17 % (1/6)
Almond 33 % (1/3), Brazil nut 33 % (1/3), hazelnut 33 % (1/3)
Walnut 24 % (10/41), Brazil nut 24 % (10/41), almond 22 % (9/41), cashew 15 % (10/41),
hazelnut 7 % (3/41), pecan 7 % (3/41)
Hazelnut 50 % (1/2), cashew 50 % (1/2)
Mexico
Bedolla-Barajas et al. 2014 [18]Walnut100%(2/2)
54 Page 10 of 13 Curr Allergy Asthma Rep (2015) 15: 54
Discussion
This review has confirmed that the majority of tree nut allergy
prevalence studies continue to be undertaken in Europe, where
there is a high prevalence of OAS, with most studies relying
on self-reported prevalence, limited to children and adoles-
cents. Using the most robust measure of tree nut prevalence
(challenge confirmed or history of reaction with IgE antibod-
ies), we estimate the overall prevalence to be <2 % in coun-
tries where OAS is not reported. Secondary tree nut allergy
(OAS) estimates for older age groups including adolescents
and adults is as high as 10 %, particularly in Europe. Few
studies reported the population prevalence of individual tree
nut allergies. However, how prevalent a particular tree nut
allergy is differs significantly by region with hazelnut the most
common tree nut allergy in Europe, walnut and cashew in the
USA and Brazil nut, almond and walnut most commonly re-
ported in the UK. There is limited evidence to determine if the
population prevalence of tree nut allergy is increasing.
This is the first systematicreview of the literature exploring
tree nut allergy prevalence exclusively across the age groups
and different regions of the world, utilising robust systematic
review methodology, closely following PRISMA guidelines.
A further strength of this review is we categorised prevalence
by robustness of the study methodology employed to define
tree nut allergy. We identified three studies with self-reported
tree nut allergy greater than 8 %, all from Europe demonstrat-
ing that studies which do not differentiate primary and sec-
ondary tree nut allergy prevalence rates are likely to inflate
prevalence estimates.
Precise estimates of true tree nut allergy were limited by the
small number of studies reporting challenge confirmed tree
nut allergy prevalencethe gold standard for diagnosis. As
for other epidemiological studies of food allergy prevalence
[8,9], we also found higher prevalence estimates for self-
report and sensitisation. Self-report is known to overestimate
the true prevalence of food allergy [54] and asymptomatic
sensitisation to foods is relatively common [9]; therefore, ob-
jective measures are critical. We were also unable to accurate-
ly determine whether tree nut allergy is on the rise as only one
series of estimates was available. Finally, estimates of the
prevalence of individual tree nut allergies could not be reliably
estimated due to the paucity of data reported for individual
nuts, although it is clear that there is significant regional var-
iation in prevalence estimates [55].
We found overall tree nut allergy prevalence mirrors the
global pattern of overall food allergy with countries with
low prevalence of food allergy also reporting low levels of
tree nut allergy. Large population-based epidemiological stud-
ies such as the ISAAC and EuroPrevall studies have demon-
strated considerable regional variability of common food al-
lergens and sensitisation patterns, but the reasons for this re-
main largely unexplored. It has been hypothesised that
variation in dietary patterns at the population level might lead
to variations in sensitisation status and hence risk of subse-
quent food allergy. Du Toit et al. hypothesised that variations
in peanut allergy prevalence between genetically similar pop-
ulations in the UK and Israel might be due to differences in
infantile peanut consumption patterns [22], whilst others have
argued thatboiled versus roasted peanut dietary intakes may at
least partly explain the difference in allergy patterns across
different regions [56,57].
Our review found a higher self-reported tree nut allergy
range (011.4 %) than both previous published systematic
reviews. Nwaru et al. performed a meta-analysis of seven
studies and reported a pooled self-reported point prevalence
of 1.8 % (95% CI 1.631.99), although there was signifi-
cant heterogeneity across the studies (I
2
=99.4 %, p=0.00).
Zuidmeer et al. included studies from a wider range of
countries from 1990 to 2006 and reported a self-reported
tree nut allergy prevalence range of 07.3 % based on
seven studies [12]. Prevalence varied based on type of tree
nut allergy, method of tree nut allergy diagnosis, age and
region. Similarly to Zudimeer et al., considering the large
heterogeneity between the studies, we have not presented a
pooled prevalence estimate since this would mask the dif-
ferences between populations.
Nwaru et al. reported confirmed tree nut allergy pooled
point prevalence of 0.45 % (I
2
=0.00 %, p=0.88) while
Zuidmeer et al. reported a range of 0.14.3, based on only
three studies. We found the prevalence of tree nut sensitisation
to be the highest of the four methods of allergy definition used
(1.012.2 %). Comparison to sensitisation prevalence esti-
mates in previous reviews is difficult as we reported sensitisa-
tion prevalence estimates based on population sensitisation.
Previous reviews both reported studies where SPT or sIgE
was performed only on participants that had previously self-
reported tree nut allergy. Neither of these reviews differentiat-
ed between primary and secondary tree nut allergy prevalence,
or reported on individual tree nut allergy prevalence nor the
nature or prevalence of multiple tree nut allergies.
In conclusion, this systematic review has highlighted
that there is considerable heterogeneity in tree nut allergy
prevalence from studies to date and pooling individual
study estimates risks masking the real differences between
populations. Data is limited to largely European, US and
UK studies using self-reported prevalence in children and
adolescents. There is a need for further studies to deter-
mine tree nut allergy by gold standard methodologies
such as food challenge, and differentiate between primary
and secondary tree nut allergy. Further detailed informa-
tion on individual tree nut prevalences will help inform
our understanding of regional variation and repeated esti-
mates over time will enable us to understand whether time
trends in tree nut allergy mirror the general rise in IgE-
mediated food allergy reported in developed countries.
Curr Allergy Asthma Rep (2015) 15: 54 Page 11 of 13 54
Acknowledgement This review forms work as part of VMc PhD,
funded by the Centre for Food and Allergy Research (CFAR).
Compliance with Ethics Guidelines
Conflict of Interest Drs McWilliam, Koplin, Lodge, Tang, Dharmage
and Allen declare no conflicts of interest.
Human and Animal Rights and Informed Consent This article does
not contain any studies with human or animal subjects performed by any
of the authors.
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... [1][2][3][4][5][6][7][8] While some food allergies (egg and milk) resolve within the first few years of life, adolescents with peanut allergy are less likely to acquire natural tolerance and are at higher risk of severe allergic reactions. [9][10][11][12] Peanut allergy tends to persist into adolescence and adulthood, often in conjunction with allergies to other foods such as tree nuts. 12 Adolescents with peanut allergy represent one of the highest risk groups for severe allergic reactions and poor quality of life. ...
... While the heterogeneous nature of the FA adolescents potentially promoted variability in the FA group, we view this heterogeneity as a strength of our study as it is an accurate representation of the FA demographic in this age group. 9,11,12 We recognize that gene expression data from the quiescent samples would have proven useful in characterizing the profile of T cell transcriptional changes in NA and FA adolescents. However, the transcriptomic differences found following activation are sufficient in portraying the differential gene expression following activation in FA adolescents. ...
Article
Background: IgE-mediated food allergies have been linked to suboptimal naïve CD4 T (nCD4T) cell activation in infancy, underlined by epigenetic and transcriptomic variation. Similar attenuated nCD4T cell activation in adolescents with food allergy have also been reported, but these are yet to be linked to specific epigenetic or transcriptional changes. Methods: We generated genome-wide DNA methylation data in purified nCD4 T cells at quiescence and following activation in a cohort of adolescents (aged 10-15 years old) with peanut allergy (peanut only or peanut + ≥1 additional food allergy) (FA, n = 29), and age-matched non-food allergic controls (NA, n = 18). Additionally, we assessed transcriptome-wide gene expression and cytokine production in these cells following activation. Results: We found widespread changes in DNA methylation in both NA and FA nCD4T cells in response to activation, associated with the T cell receptor signaling pathway. Adolescents with FA exhibit unique DNA methylation signatures at quiescence and post-activation at key genes involved in Th1/Th2 differentiation (RUNX3, RXRA, NFKB1A, IL4R), including a differentially methylated region (DMR) at the TNFRSF6B promoter, linked to Th1 proliferation. Combined analysis of DNA methylation, transcriptomic data and cytokine output in the same samples identified an attenuated interferon response in nCD4T cells from FA individuals following activation, with decreased expression of several interferon genes, including IFN-γ and a DMR at a key downstream gene, BST2. Conclusion: We find that attenuated nCD4T cell responses from adolescents with food allergy are associated with specific epigenetic variation, including disruption of interferon responses, indicating dysregulation of key immune pathways that may contribute to a persistent FA phenotype. However, we recognize the small sample size, and the consequent restraint on reporting adjusted p-value statistics as limitations of the study. Further study is required to validate these findings.
... Among symptomatic reactions to nuts, anaphylaxis is very common representing around 70 %-80 % of fatal food-induced reactions [4].The consumption of nuts is very extended in the world by their high nutritional content. Thus, the worldwide prevalence described to tree nut allergy is between 0.05 % and 4.9 % [5] and peanut allergy ranging from 0.5 % to 3 % [2]. Therefore, nut allergy is a relevant health issue and its diagnosis based in clinical symptoms as well as in vivo and in vitro sensitization tests must be performed properly [6]. ...
... Geographic differences and environmental local factors represent in nut allergy an important issue to take into consideration in the clinical and laboratory management of patients [6]. In European countries the nut most prevalent in food allergy is hazelnut, followed by peanut, walnut, almond, pistachio and lastly cashew as the least frequent [5][6]19]. In similar way, hazelnut, peanut and walnut represent the first, second and third allergen source respectively in adult population with nut allergy from Spain [19]. ...
Article
Background ALEX multiplex platform has been recently commercialized but its clinical utility as quantitative technique respect to ImmunoCAP-singleplex as the reference method has not yet been confirmed on patients suffering from nut allergy and co-sensitization to different nuts. Methods 58 serum samples from patients with nut allergy from a Mediterranean population were assayed in parallel by ALEX-multiplex and ImmunoCAP-singleplex techniques. Patients were diagnosed based on clinical symptoms and positive skin prick tests (SPTs). The following whole extracts were compared between both techniques: walnut, hazelnut, peanut, almond, pistachio and sunflower seed; besides the recombinant Pru p 3. A qualitative and quantitative study was carried out. Results Both techniques had similar sensitivities respect to whole extracts from walnut, hazelnut and peanut as well as to Pru p 3 (p > 0.05). However for whole extracts from almond, pistachio and sunflower seed the sensitivity obtained by ALEX was much lower than ImmunoCAP (9.09 % vs 88.63 %; 14.81 vs 70.37 %; and 8.51 % vs 88.88 %; respectively). The concordance between both techniques showed only a substantial agreement for Pru p 3 (k = 0.791); moderate agreement for hazelnut and peanut (k = 0.550 and k = 0.544, respectively); fair agreement for walnut (k = 0.386) and poor agreement for almond, pistachio and sunflower seed (k < 0.2). Quantitative analysis showed that ImmunoCAP for walnut, peanut and sunflower seed had higher mean values than ALEX. Relationships were significant for all specific IgE levels except to for almond, pistachio and sunflower seed. Conclusions ALEX platform is a suitable technique to patients with nut allergy from the Mediterranean area except to for those suffering from allergy to almond, pistachio and sunflower seed.
... Although sterilization can be done to minimize the presence of these pathogens, still both these pathogens can cause a considerable reduction in nutritive value (Van Impe et al., 2018). Moreover, being a tree nut, almond allergy is common and ranked as the fourth most common tree nut allergy in the USA (Mcwilliam et al., 2015). The almond allergic responses can vary from mild such as simple oral allergy to very complex such as fatal anaphylaxis. ...
Chapter
Plant-based beverages are gaining popularity among consumers who are seeking alternative and environmentally sustainable options to traditional dairy drinks. The food industry is therefore developing a range of affordable, convenient, desirable, nutritional, and sustainable plant-based milk alternatives. This chapter provides an overview of the current knowledge on fundamental processing steps to convert plant material into plant-based beverages, what are processing challenges for different plant sources, how to overcome these challenges and potential quality deficiencies, and what are the opportunities to maximize textural, nutritional, and sensory aspects of plant-based beverages.
... Hazelnut allergy prevalence was understudied until recently, despite its clinical importance. Studies have shown that prevalence of hazelnut allergy depends on the patients' age and their geographical location [1]. Cor a 9, the 11S globulin, is one of the major hazelnut allergens, inducing upon ingestion moderate to severe symptoms in individuals allergic to hazelnut. ...
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Most of the food allergens sensitized via the gastrointestinal tract resist thermal treatments and digestion, particularly digestion by pepsin. Roasted hazelnuts are more commonly consumed than raw ones. Since no studies have characterized gastric digestion protein fragments of raw and roasted hazelnuts nor their IgE binding properties, we compared these aspects of raw and roasted hazelnuts’ gastric digesta obtained by INFOGEST protocol. Their electrophoretically resolved profiles were probed with hazelnut allergic patients’ sera in 1D and 2D immunoblots. Electrophoretic profiles demonstrated pepsin digestion of all hazelnut allergens to varying extents. While 2D immunoblots indicated that roasting slightly reduced allergenicity, IgE ELISA with the pool of sera showed a slight significant (10%) increase in IgE binding in both gastric digesta. Cor a 9 isolated from the raw and roasted hazelnuts, characterized by far and near CD, remained stable after roasting, with preserved IgE reactivity. Its immunoreactivity contribution by inhibitory ELISA was noticeable in raw and roasted hazelnut digesta; its activity was slightly stronger in the roasted preparations. Roasting has a visible impact on proteins; however, it did not affect overall IgE reactivity. Gastric digestion slightly increases the overall IgE reactivity in raw and roasted hazelnuts, and may therefore impact the profiles of allergens and their fragments available to interact with the immune system in the small intestine.
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The global food market needs to grow and supply food demand to feed the growing world population. Alternative food proteins, including novel sources of safe foods and ingredients, are the candidates that could provide more environmentally sustainable choices, animal welfare, and consumers health. Novel foods and food proteins must undergo premarket safety evaluations including allergenicity assessment to reduce the risk of cross-reactivity with known allergens and uncharacterized risk to food allergic individuals. This research addressed the safety assessment of some novel foods and food ingredients using the study of stability of proteins in pepsin and sequence identity analysis in the AllergenOnline database. Subject samples included microalgae, hemp heart protein, sweet protein, and manganese related peroxidase. In addition, food allergy is a complicated and multifactorial disease. Safety evaluation based on the IgE binding, as a part of risk assessments required by CODEX for the protein sequence identity matches of >35%, usually overestimates the true cross-reactivity due to the false positive results. The results of this study revealed that in vitro protein stability in pepsin in conjunction with other safety assessments can suggest a positive predictive value for a putative food allergen. The proposed approach described in this thesis included a combination of assays of protein stability in pepsin and meaningful sequence identity matches. Serum IgE binding evaluations would be useful when the match criteria are >50% sequence identity in a full sequence. For the biological relevance of these assessments, serum inhibition western blot analysis and basophil activation test (BAT) using humanized rat basophilic (hRBL) cell line can improve the accuracy of food safety assessment for the risk of novel food proteins. The combination of all methods used in this study would help to propose a better approach for food security and premarket evaluations of novel food proteins. Advisor: Richard E. Goodman
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Food allergy is affecting 5-8% of young children and 2-4% of adults and seems to be increasing in prevalence. The cause of the increase in food allergy is largely unknown but proposed to be influenced by both environmental and lifestyle factors. Changes in intestinal barrier functions and increased uptake of dietary proteins have been suggested to have a great impact on food allergy. In this review, we aim to give an overview of the gastrointestinal digestion and intestinal barrier function and provide a more detailed description of intestinal protein uptake, including the various routes of epithelial transport, how it may be affected by both intrinsic and extrinsic factors, and the relation to food allergy. Further, we give an overview of in vitro, ex vivo and in vivo techniques available for evaluation of intestinal protein uptake and gut permeability in general. Proteins are digested by gastric, pancreatic and integral brush border enzymes in order to allow for sufficient nutritional uptake. Absorption and transport of dietary proteins across the epithelial layer is known to be dependent on the physicochemical properties of the proteins and their digestion fragments themselves, such as size, solubility and aggregation status. It is believed, that the greater an amount of intact protein or larger peptide fragments that is transported through the epithelial layer, and thus encountered by the mucosal immune system in the gut, the greater is the risk of inducing an adverse allergic response. Proteins may be absorbed across the epithelial barrier by means of various mechanisms, and studies have shown that a transcellular facilitated transport route unique for food allergic individuals are at play for transport of allergens, and that upon mediator release from mast cells an enhanced allergen transport via the paracellular route occurs. This is in contrast to healthy individuals where transcytosis through the enterocytes is the main route of protein uptake. Thus, knowledge on factors affecting intestinal barrier functions and methods for the determination of their impact on protein uptake may be useful in future allergenicity assessments and for development of future preventive and treatment strategies.
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Background: Peanuts (PN) and tree nuts (TN) are major causes of anaphylaxis worldwide. We aimed to determine the clinical and demographic characteristics associated with anaphylaxis in patients sensitized to PN and/or TN in a Mediterranean population. Methods: We conducted a retrospective study, which included 198 patients allergic to PN and/or TN (allergy symptoms plus specific immunoglobulin E [sIgE] sensitization), evaluated in consultations from January 2015 to December 2020. Univariate analysis and multivariate logistic regression models were developed, including demographic, clinical, and laboratory data as independent variables, and anaphylaxis to each PN and/or TN as a dependent variables. Results: Anaphylaxis was associated with an earlier age of onset of allergy to PN, cashew and/or pistachio, and pine nut allergy but not to other TN allergies. Gender, atopic comorbidities, and cofactors were not associated with PN and/or TN anaphylaxis. Anaphylaxis to PN, cashew and/or pistachio, and pine nut were associated with reactivity to a fewer number of PN and/or TN foods. Although sIgE sensitization to lipid transfer proteins (LTP) was highly prevalent in our population, only seed storage protein (SSP) positivity was associated with anaphylaxis in PN allergy. The absence of pathogenesis-related protein family 10 sensitization correlated with PN and hazelnut anaphylaxis. A higher level of sIgE to almond extract predicted anaphylaxis but the level of sIgE to other PN and/or TN extracts did not predict it. Conclusion: The high prevalence of sensitization to the pan-allergen LTP did not seem to have a significant impact in PN and/or TN allergy severity in our study. Instead, other factors, such as early age of onset and positivity for SSPs, seem to strongly associate with anaphylaxis to specific PN and/or TN. These findings may contribute to individual risk assessment in these populations.
Chapter
Nuts are nutrient-dense foods. They are good sources of plant protein, unsaturated fats, fiber, vitamins and minerals. In botanical terms, the word “nut” is used to describe a wide range of seeds, mostly from trees; however, there are some exceptions, such as peanuts that are considered a legume. Most commonly eaten nuts are almonds, Brazil nuts, cashews, hazelnuts, pecans, peanuts, pine nuts, pistachios, walnuts and macadamias. Nuts and seeds come from a diverse range of different plants (vegetables, flowers, or crops grown for a variety of uses), so their nutritional composition is quite varied. Seeds, such as pumpkin seeds, sesame and sunflower, are sources of plant protein, unsaturated fatty acids, fiber, minerals and vitamins). Thanks to their nutrient-dense profile, nut consumption has been associated with several health benefits, such as better lipid profile (lower cholesterol and triglyceride levels) and improved endothelial function and overall cardiovascular health, a reduction of postprandial glycaemia and insulin resistance (type 2 diabetes prevention), and delay in age-related cognitive decline, among other health conditions. Nuts and seeds have a wide range of uses. In the typical Western diet or Mediterranean diet they tend to be used either as snack or added as minor ingredients to savory and sweet dishes, but they have wider applications in vegetarian and other plant-based diets as important sources of plant protein and other nutrients. Certain nuts and seeds are also made into spreads, for example peanut butter and tahini (sesame seed spread) or vegan “cheeses” (mainly made by cashew paste).
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Background: Despite the high risk of anaphylaxis in patients with a macadamia nut allergy (MdA), little is known about the significance of macadamia nut-specific immunoglobulin E (Md-sIgE). Thus, this study aimed to investigate the utility of Md-sIgE for predicting anaphylaxis. Methods: Children with suspected MdA who visited our hospital were included. MdA was defined as either failing the 3-g macadamia nut (Md) oral food challenge (OFC) or confirming obvious immediate symptoms following Md ingestion. Non-MdA was defined as passing the 3-g Md OFC. Results: A total of 41 children (29 [71%] males) with a median age of 7.7 years were included. The median Md-sIgE level was 2.23 kUA /L. Among the 21 children diagnosed with MdA, eight and 13 children did (An group) and did not (non-An group) develop anaphylaxis. Twenty children were included in the non-MdA group. The Md-sIgE level was significantly higher in the An group relative to the others (7.97 vs. 1.92 kUA /L, p < .001). Furthermore, the Md-sIgE level was significantly higher in the An group than in the non-An group (7.97 vs. 1.92 kUA /L, p = .02). However, there was no significant difference in the Md-sIgE between the non-An and non-MdA groups (1.92 vs. 1.90 kUA /L, p > .99). The area under the curve for predicting anaphylaxis in Md-sIgE was 0.92 (95% CI: 0.83-1.00), and the optimal cut-off value was 3.76 kUA /L. Conclusion: Md-sIgE levels were useful in predicting anaphylaxis. Above the cut-off value, we emphasize paying careful attention to the risk of anaphylaxis.
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Consumption of nuts and seeds is associated with a range of health outcomes. Summarizing the best evidence on essential health outcomes from the consumption of nuts is essential to provide optimal recommendations. Our objective is to comprehensively assess health outcomes associations related to the consumption of nuts and seeds, using a culinary definition including tree nuts and peanuts (registered in PROSPERO: CRD42021258300). Health outcomes of interest include cardiovascular disease, cancer, diabetes, obesity, respiratory disease, mortality, and their biomarker for disease. We present associations for high versus low consumption, per serving, and dose-response relationships. Medline, Embase, Cochrane, and Epistemonikos were searched and screened for systematic reviews and meta-analyses. Evidence was extracted from 89 articles on the consumption of nuts and relevant health outcomes, including 23 articles with meta-analysis on disease and mortality, 66 articles on biomarkers for disease, and 9 articles on allergy/adverse outcomes. Intake of nuts was associated with reduced risk of cardiovascular diseases and related risk factors, with moderate quality of evidence. An intake of 28 grams of nuts per day compared to not eating nuts was associated with a 21% relative risk reduction of cardiovascular disease (including coronary heart disease incidence and mortality, atrial fibrillation, and stroke mortality), 11% risk reduction of cancer deaths, and 22% reduction in all-cause mortality. Nut consumption was also inversely associated with mortality from respiratory diseases, infectious diseases, and diabetes: however, associations between nut consumption and diabetes incidence were mixed. Meta-analyses of trials on biomarkers for disease generally mirrored meta-analyses from observational studies on cardiovascular disease, cancers, and diabetes. Allergy and related adverse reactions to nuts were observed among 1–2% of adult populations, with substantial heterogeneity between studies. Overall, the current evidence supports dietary recommendations to consume a handful of nuts and seeds per day for people without allergies to these foods.
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Food allergies in children present with a wide spectrum of clinical manifestations, including anaphylaxis, urticaria, angioedema, atopic dermatitis and gastrointestinal symptoms (such as vomiting, diarrhoea and failure to thrive). Symptoms usually begin in the first 2 years of life, often after the first known exposure to the food. Immediate reactions (occurring between several minutes and 2 hours after ingestion) are likely to be IgE-mediated and can usually be detected by skin prick testing (SPT) or measuring food-specific serum IgE antibody levels. Over 90% of IgE-mediated food allergies in childhood are caused by eight foods: cows milk, hens egg, soy, peanuts, tree nuts (and seeds), wheat, fish and shellfish. Anaphylaxis is a severe and potentially life-threatening form of IgE-mediated food allergy that requires prescription of self-injectable adrenaline. Delayed-onset reactions (occurring within several hours to days after ingestion) are often difficult to diagnose. They are usually SPT negative, and elimination or challenge protocols are required to make a definitive diagnosis. These forms of food allergy are not usually associated with anaphylaxis. The mainstay of diagnosis and management of food allergies is correct identification and avoidance of the offending antigen. Children often develop tolerance to cows milk, egg, soy and wheat by school age, whereas allergies to nuts and shellfish are more likely to be lifelong.
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Systematic reviews should build on a protocol that describes the rationale, hypothesis, and planned methods of the review; few reviews report whether a protocol exists. Detailed, well-described protocols can facilitate the understanding and appraisal of the review methods, as well as the detection of modifications to methods and selective reporting in completed reviews. We describe the development of a reporting guideline, the Preferred Reporting Items for Systematic reviews and Meta-Analyses for Protocols 2015 (PRISMA-P 2015). PRISMA-P consists of a 17-item checklist intended to facilitate the preparation and reporting of a robust protocol for the systematic review. Funders and those commissioning reviews might consider mandating the use of the checklist to facilitate the submission of relevant protocol information in funding applications. Similarly, peer reviewers and editors can use the guidance to gauge the completeness and transparency of a systematic review protocol submitted for publication in a journal or other medium.
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Purpose There is limited epidemiological evidence of food hypersensitivity (FH) in the adult population. We aimed to determine the prevalence of FH in Mexican adults, their clinical features and to establish common food involved in its appearance. Methods We designed a cross-sectional study using a fixed quota sampling; 1,126 subjects answered a structured survey to gather information related to FH. Results The prevalence of FH in adults was 16.7% (95% CI, 14.5% to 18.8%), without statistical significant differences related to gender (women, 17.5% and men, 15.9%) or residential location. The most common clinical manifestations in adults with FH were oral allergy syndrome (70 of 1,126) and urticaria (55 of 1,126). According to category, fruits and vegetables were the most frequent foods to trigger FH (6.12%) and were individually related to shrimp (4.0%), and cow milk (1.5%). Adults under age 25 had a higher frequency of FH (OR, 1.39; 95% CI, 1.01 to 1.91, P <0.001). Personal history of any atopic disease was significantly associated with FH (P <0.0001). Conclusions The prevalence of FH is relatively high in Mexican adults, and FH is significantly associated with atopic diseases.
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Allergy to cow's milk, egg, wheat, soy, peanut, tree nuts, fish, and shellfish constitutes the majority of food allergy reactions, but reliable estimates of their prevalence are lacking. This systematic review aimed to provide up-to-date estimates of their prevalence in Europe.Studies published in Europe from January 1, 2000, to September 30, 2012, were identified from searches of four electronic databases. Two independent reviewers appraised the studies and extracted the estimates of interest. Data were pooled using random-effects meta-analyses. Fifty studies were included in a narrative synthesis and 42 studies in the meta-analyses. Although there were significant heterogeneity between the studies, the overall pooled estimates for all age groups of self-reported lifetime prevalence of allergy to cow's milk, egg, wheat, soy, peanut, tree nuts, fish, and shellfish were 6.0% (95% confidence interval: 5.7–6.4), 2.5% (2.3–2.7), 3.6% (3.0–4.2), 0.4% (0.3–0.6), 1.3% (1.2–1.5), 2.2% (1.8–2.5), and 1.3% (0.9–1.7), respectively. The prevalence of food-challenge-defined allergy to cow's milk, egg, wheat, soy, peanut, tree nuts, fish, and shellfish was 0.6% (0.5–0.8), 0.2% (0.2–0.3), 0.1% (0.01–0.2), 0.3% (0.1–0.4), 0.2% (0.2–0.3), 0.5% (0.08–0.8), 0.1% (0.02–0.2), and 0.1% (0.06–0.3), respectively. Allergy to cow's milk and egg was more common among younger children, while allergy to peanut, tree nuts, fish, and shellfish was more common among the older ones. There were insufficient data to compare the estimates of soy and wheat allergy between the age groups. Allergy to most foods, except soy and peanut, appeared to be more common in Northern Europe. In summary, the lifetime self-reported prevalence of allergy to common foods in Europe ranged from 0.1 to 6.0%. The heterogeneity between studies was high, and participation rates varied across studies reaching as low as <20% in some studies. Standardizing the methods of assessment of food allergies and initiating strategies to increase participation will advance this evidence base.
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While food allergies and eczema are among the most common chronic non-communicable diseases in children in many countries worldwide, quality data on the burden of these diseases is lacking, particularly in developing countries. This 2012 survey was performed to collect information on existing data on the global patterns and prevalence of food allergy by surveying all the national member societies of the World Allergy Organisation, and some of their neighbouring countries. Data were collected from 89 countries, including published data, and changes in the health care burden of food allergy. More than half of the countries surveyed (52/89) did not have any data on food allergy prevalence. Only 10% (9/89) of countries had accurate food allergy prevalence data, based on oral food challenges (OFC). The remaining countries (23/89) had data largely based on parent-reporting of a food allergy diagnosis or symptoms, which is recognised to overestimate the prevalence of food allergy. Based on more accurate measures, the prevalence of clinical (OFC proven) food allergy in preschool children in developed countries is now as high as 10%. In large and rapidly emerging societies of Asia, such as China, where there are documented increases in food allergy, the prevalence of OFC-proven food allergy is now around 7% in pre-schoolers, comparable to the reported prevalence in European regions. While food allergy appears to be increasing in both developed and developing countries in the last 10--15 years, there is a lack of quality comparative data. This survey also highlights inequities in paediatric allergy services, availability of adrenaline auto-injectors and standardised National Anaphylaxis Action plans. In conclusion, there remains a need to gather more accurate data on the prevalence of food allergy in many developed and developing countries to better anticipate and address the rising community and health service burden of food allergy.
Article
Allergy to cow's milk, egg, wheat, soy, peanut, tree nuts, fish, and shellfish constitutes the majority of food allergy reactions, but reliable estimates of their prevalence are lacking. This systematic review aimed to provide up-to-date estimates of their prevalence in Europe.Studies published in Europe from January 1, 2000, to September 30, 2012, were identified from searches of four electronic databases. Two independent reviewers appraised the studies and extracted the estimates of interest. Data were pooled using random-effects meta-analyses. Fifty studies were included in a narrative synthesis and 42 studies in the meta-analyses. Although there were significant heterogeneity between the studies, the overall pooled estimates for all age groups of self-reported lifetime prevalence of allergy to cow's milk, egg, wheat, soy, peanut, tree nuts, fish, and shellfish were 6.0% (95% confidence interval: 5.7–6.4), 2.5% (2.3–2.7), 3.6% (3.0–4.2), 0.4% (0.3–0.6), 1.3% (1.2–1.5), 2.2% (1.8–2.5), and 1.3% (0.9–1.7), respectively. The prevalence of food-challenge-defined allergy to cow's milk, egg, wheat, soy, peanut, tree nuts, fish, and shellfish was 0.6% (0.5–0.8), 0.2% (0.2–0.3), 0.1% (0.01–0.2), 0.3% (0.1–0.4), 0.2% (0.2–0.3), 0.5% (0.08–0.8), 0.1% (0.02–0.2), and 0.1% (0.06–0.3), respectively. Allergy to cow's milk and egg was more common among younger children, while allergy to peanut, tree nuts, fish, and shellfish was more common among the older ones. There were insufficient data to compare the estimates of soy and wheat allergy between the age groups. Allergy to most foods, except soy and peanut, appeared to be more common in Northern Europe. In summary, the lifetime self-reported prevalence of allergy to common foods in Europe ranged from 0.1 to 6.0%. The heterogeneity between studies was high, and participation rates varied across studies reaching as low as <20% in some studies. Standardizing the methods of assessment of food allergies and initiating strategies to increase participation will advance this evidence base.
Article
Complaints of 'food allergy' are increasing. Standardized surveys of IgE sensitization to foods are still uncommon and multicountry surveys are rare. We have assessed IgE sensitization to food-associated allergens in different regions of Europe using a common protocol. Participants from general populations aged 20-54 years in eight European centres (Zurich, Madrid, Utrecht, Lodz, Sophia, Athens, Reykjavik and Vilnius) were asked whether they had allergic symptoms associated with specific foods. Weighted samples of those with and without allergic symptoms then completed a longer questionnaire and donated serum for IgE analysis by ImmunoCAP for 24 foods, 6 aeroallergens and, by allergen microarray, for 48 individual food proteins. The prevalence of IgE sensitization to foods ranged from 23.6% to 6.6%. The least common IgE sensitizations were to fish (0.2%), milk (0.8%) and egg (0.9%), and the most common were to hazelnut (9.3%), peach (7.9%) and apple (6.5%). The order of prevalence of IgE sensitization against different foods was similar in each centre and correlated with the prevalence of the pollen-associated allergens Bet v 1 and Bet v 2 (r = 0.86). IgE sensitization to plant allergen components unrelated to pollen allergens was more evenly distributed and independent of pollen IgE sensitization (r = -0.10). The most common foods containing allergens not cross-reacting with pollens were sesame, shrimp and hazelnut. IgE sensitization to foods is common, but varies widely and is predominantly related to IgE sensitization to pollen allergens. IgE sensitization to food allergens not cross-reacting with pollens is rare and more evenly distributed.
Article
1534-4436 Taylor-Black, Sarah A Mehta, Harshna Weiderpass, Elisabete Boffetta, Paolo Sicherer, Scott H Wang, Julie K23 AI082883/AI/NIAID NIH HHS/United States K23 AI083883/AI/NIAID NIH HHS/United States UL1 TR-000067/TR/NCATS NIH HHS/United States Letter Research Support, N.I.H., Extramural United States Ann Allergy Asthma Immunol. 2014 Jun;112(6):554-556.e1. doi: 10.1016/j.anai.2014.03.020. Epub 2014 Apr 24.