A cross-sectional study on the prevalence of food allergy to eggplant (Solanum melongena L.) reveals female predominance.

Abstract

Only a few case reports of allergy to eggplant (Solanum melongena) have been reported. A relatively large number of individuals appear to experience food-related symptoms to eggplant in India.
The major aims of this study are to assess the prevalence of food allergy to eggplant and analyse the age and gender distribution.
Seven hundred and forty-one subjects (age range: 5-60 years) randomly selected from rural and urban areas of Mysore city were analysed for the prevalence of eggplant allergy based on case history, skin prick test (SPT) with eggplant extracts and allergen-specific IgE. The age and gender distribution for the prevalence of eggplant allergy and its association with other atopic conditions were assessed.
Sixty-eight (9.2%) subjects reported adverse reactions to ingestion of eggplant, of which 32 (4.3%) subjects had positive history/positive SPT and 36 (4.9%) had positive history/negative SPT. Sixteen (2.2%) subjects had negative history/positive SPT. Ten subjects (1.4%) experienced allergic symptoms in <2 h. Sensitization to eggplant by SPT was more in atopic (16.7%) compared with non-atopic subjects (3.8%). All the SPT-positive subjects (n=48) underwent evaluation for eggplant allergen-specific IgE, which was detected in 6 subjects (0.8%). Majority of the subjects sensitized to eggplant were in the age groups 16-45 years, and females were twice as likely to be sensitized as males. Female predominance (4 : 1) is more in the 16-30 year group.
Many subjects experience adverse reactions to the ingestion of eggplant, possibly due to the pharmacologic action of histamine and other non-protein components, rather than to specific protein allergen(s). The prevalence of IgE-mediated eggplant allergy is estimated at approximately 0.8%, with higher rates of sensitization in females.

Full text

Page 1

ORIGINAL PAPER
A cross-sectional study on the prevalence of food allergy to eggplant
(Solanum melongena L.) reveals female predominance
B. N. Harish Babu?, P. A. Maheshwand Y. P. Venkatesh?
?Department of Biochemistry and Nutrition, Central Food Technological Research Institute (CFTRI), Council of Scientific and Industrial Research (CSIR), Mysore,
Karnataka, India andwAllergy, Asthma and Chest Centre, Mysore, Karnataka, India
Clinical and
Experimental
Allergy
Correspondence:
Yeldur P. Venkatesh, Department of
Biochemistry and Nutrition, Central
Food Technological Research Institute
(CFTRI), Council of Scientific and
Industrial Research (CSIR), KRS Road,
Mysore 570020, Karnataka, India.
E-mail: venkatyp@yahoo.com
Cite this as: B. N. Harish Babu,
P. A. Mahesh and Y. P. Venkatesh,
ClinicalandExperimentalAllergy, 2008
(38) 1795–1802.
Summary
Background Only a few case reports of allergy to eggplant (Solanum melongena) have been
reported. A relatively large number of individuals appear to experience food-related
symptoms to eggplant in India.
Objective The major aims of this study are to assess the prevalence of food allergy to eggplant
and analyse the age and gender distribution.
Methods Seven hundred and forty-one subjects (age range: 5–60 years) randomly selected
from rural and urban areas of Mysore city were analysed for the prevalence of eggplant
allergy based on case history, skin prick test (SPT) with eggplant extracts and allergen-specific
IgE. The age and gender distribution for the prevalence of eggplant allergy and its association
with other atopic conditions were assessed.
Results Sixty-eight (9.2%) subjects reported adverse reactions to ingestion of eggplant, of
which 32 (4.3%) subjects had positive history/positive SPTand 36 (4.9%) had positive history/
negative SPT. Sixteen (2.2%) subjects had negative history/positive SPT. Ten subjects (1.4%)
experienced allergic symptoms in o2h. Sensitization to eggplant by SPT was more in atopic
(16.7%) compared with non-atopic subjects (3.8%). All the SPT-positive subjects (n=48)
underwent evaluation for eggplant allergen-specific IgE, which was detected in 6 subjects
(0.8%). Majority of the subjects sensitized to eggplant were in the age groups 16–45 years, and
females were twice as likely to be sensitized as males. Female predominance (4:1) is more in
the 16–30 year group.
Conclusions Many subjects experience adverse reactions to the ingestion of eggplant, possibly
due to the pharmacologic action of histamine and other non-protein components, rather than
to specific protein allergen(s). The prevalence of IgE-mediated eggplant allergy is estimated at
?0.8%, with higher rates of sensitization in females.
Keywords allergen-specific IgE, eggplant, food allergy, gender, prevalence, skin prick test
Submitted 6 March 2008; revised 7 May 2008; accepted 6 June 2008
Introduction
Even though most of the world’s population lives in Asia,
there is a paucity of scientific data on the prevalence and
clinical features of food allergy, mainly due to (1) lack of
awareness of the problem, and (2) lack of large, well-
designed epidemiological studies. For many years, it was
believed that the prevalence of allergic diseases, including
food allergy, was low in Asia. Recent studies describing
the pattern of anaphylaxis and the role of food triggers
show that food is an important cause of severe allergic
reactions in Asia [1]. Although about one-third of the
world’s population perceives that it is allergic to one or
more foods, the actual incidence of food allergy is
estimated at 2–4% in adults and 6–8% in children [2].
Allergy to milk, egg and seafood is universal to all the
countries. There are, however, some unique and unusual
food allergies first described in Asia, but are not seen in
other countries. These foods include bird’s nest (edible
nests of swiftlets belonging to Collocalia spp., Singapore);
buckwheat (Fagopyrum esculentum, China); chickpea
(Cicer arietinum, India); black gram (Vigna mungo, India);
lima bean (Phaseolus lunatus, India); rice (Oryza sativa,
Japan and India) and sesame (Sesamum indicum, Israel)
[3–10]. In addition, a large population world-wide has
Clinical Allergy
Clinical and Experimental Allergy, 38, 1795–1802
doi: 10.1111/j.1365-2222.2008.03076.x
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd

Page 2

reported allergic reactions to ingestion of Solanaceous
vegetables, namely, potato, tomato and bell pepper, and
several allergens have been identified [11]. In contrast,
hypersensitivity reactions to ingestion of eggplant have
only been reported in a few case studies [12–15], and are
attributed to cross-reactivity with tomato, latex and grass/
weed pollens.
Eggplant (aubergine, brinjal, Solanum melongena), po-
pularly known as ‘poor man’s meat’ in the Indian sub-
continent, ranks twelfth among the leading vegetable
crops of the world [16, 17]. Consumed widely in Asia and
Europe, it is used primarily as a cooked vegetable. A
considerable number among the Indian population often
perceive adverse reactions to eggplant. Therefore, we
decided to study the prevalence of allergy to ingestion of
eggplant based on detailed case history, skin prick test
(SPT) and the presence of allergen-specific IgE. Here, we
report the prevalence of eggplant allergy in relation to
age, gender and its association with atopic history of
study subjects in a random population residing in and
around Mysore city.
Materials and methods
Selection of subjects
Seven hundred and forty-one individuals in the age range
5–60 years were recruited randomly from rural and
urban areas of Mysore city (Mysore district, Karnataka,
India) for screening of food-allergic reactions to eggplant.
A detailed case history of the subjects was taken based on
a structured questionnaire containing information regard-
ing age, gender, occupation, age at onset of disease and
the present status. In addition, type of complaints [cuta-
neous (C), respiratory (R), gastrointestinal (GI) and/or
neurological (N)], allergy to other foods, house dust mite
(HDM) and/or pollens, allergy to insects, contact agents
and duration of onset of allergic symptoms after ingestion
of the offending food were recorded. Atopy was defined as
having a positive SPT to any one of the following: HDM,
grass/weed pollen and insects. The study was undertaken
following approval by the Institutional Ethics Committee.
Preparation of allergenic extracts from eggplant
Freshly obtained, local variety (Mysore green) of eggplant
having greenish, long appearance was used. Eggplant
extract was prepared by blending 50g eggplants in a
blender using 50mL of 10mM sodium phosphate buffer,
pH 7.4, containing 140mM NaCl (PBS) and 100mM
L-ascorbic acid (to prevent enzymic browning reaction),
centrifuged at 5300?g for 20min, filtered through What-
man no. 1 filter, lyophilized, stored at ?201C and portions
of it were reconstituted before SPT (eggplant extract
prepared this way is designated as EE hereafter). Addi-
tionally, the EE was dialysed using 12–14kDa cut-off
membrane against three changes of double-distilled water
and subjected to acetone precipitation. The precipitate was
resolubilized in PBS; this is designated as eggplant con-
centrate (EC). Both the extract and the concentrate were
glycerinated to a final concentration of 50% v/v, and the
protein content of the extracts used for SPT was adjusted
to 0.5mg/mL. Because SPT reactivity and allergen-speci-
fic IgE detection in eggplant-allergic cases were similar
with both raw and cooked EEs in our earlier study [12],
only raw EE was used for testing in this study.
Skin prick test using eggplant extracts
SPT was performed as per the standard procedure [18]
using sterile prick lancetter (Bayer Pharmaceutical Divi-
sion, Spokane, WA, USA). Eggplant allergenic extracts, EE
and EC, along with controls (positive: histamine dihy-
drochloride equivalent to 1mg/mL histamine base, and
negative: 50% glycerinated PBS) were used for SPT. Each
sample was pricked with a separate sterile lancet to avoid
carryover of the sample. The weal and flare diameters
were measured after 20min. A weal diameter of 43mm
compared with negative control was considered as posi-
tive prick test. Because prick-to-prick (PTP) test produced
slightly lower response compared with SPT in the case of
three eggplant-allergic subjects in our earlier study [12],
only SPT was used in this study.
Detection of allergen-specific immunoglobulin E
Detection of allergen-specific IgE by direct ELISA [19] was
carried out using sera from SPT-positive subjects. Micro-
titre wells (Maxisorp; Nunc, Roskilde, Denmark) were
coated at 41C overnight with EE (?30mg protein/well)
that had been dialysed using 3.5kDa cut-off membrane
against 100mM carbonate–bicarbonate buffer, pH 9.6, as
per our earlier studies [12, 15]. This was followed by
incubation with 100mL allergic or normal serum (1:3
dilution). Alkaline phosphatase-conjugated mouse anti-
human IgE (Sigma-Aldrich Co., St Louis, MO, USA) was
used as the secondary antibody (1:1000 dilution). The
absorbance was measured at 405nm using p-nitrophenyl
phosphate as the substrate. When the A405values were
twofold higher than those of normal subject’s sera (serum
pooled from five healthy subjects), the ELISA was con-
sidered positive.
Statistical analysis
To test differences in proportions between groups, the
chi-square test was used. The Student’s t-test and, when
appropriate, one-way analysis of variance (ANOVA) were
used to assess differences in means between groups. A
P-value of o0.05 was considered to be statistically
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd, Clinical and Experimental Allergy, 38:1795–1802
1796 B. N. Harish Babu et al

Page 3

significant. All the statistical analyses were done using
a software SPSS version 10 (SPSS Inc., Chicago, IL,
USA).
Results
In the present study, a total of 741 subjects were screened
for food-allergic reactions to ingestion of eggplant based
on detailed case history, SPT and presence of eggplant
allergen-specific IgE. Subject demographic characteris-
tics are indicated in Table 1. The study population
comprised 304 (41%) rural and 437 (59%) urban indivi-
duals. The gender distribution was nearly equal (males
52%, females 48%). The population comprised 586
(79.1%) healthy normal subjects and 155 (20.9%) with a
history of atopy.
Analysis of adverse reactions to eggplant ingestion
Among the 741 subjects screened, 68 subjects (9.2%)
reported adverse reaction to ingestion of eggplant. The
organ systems affected as reported by the subjects with a
positive history include mostly cutaneous (58.8%), re-
spiratory (29.4%), gastrointestinal (14.7%), pharyngeal
(10.3%) and ocular (8.9%). The clinical symptoms experi-
enced by the subjects are indicated in Table 2. When the
duration of onset of adverse reactions or allergic symp-
toms after the ingestion of eggplant was considered, only
10 (15%) out of 68 subjects with a positive history
reported experiencing allergic symptoms within 2h of
ingestion on multiple occasions, which accounts for 1.4%
of the total population analysed for eggplant allergy, and
85% of the subjects with a positive history experienced
mostly delayed reactions after 4h.
Both case history and SPT were positive in 32 (4.3%)
subjects. In case of 36 (4.9%) subjects, history was
positive, but SPT was negative. Although 16 (2.2%)
subjects had no prior experience of adverse reactions to
eggplant, SPT was positive, indicating possibility of
asymptomatic sensitization in some subjects (Table 3).
Skin prick test reactivity
Significant differences were observed in the number of
SPT-positive and SPT-negative subjects (Po0.01) in the
overall population screened for eggplant allergy. This was
also true when the individual age group was considered
separately. SPT with EE was positive in 48 (6.5%) subjects,
while the remaining 693 (93.5%) subjects had a negative
prick test. There was no significant difference observed
between rural and urban subjects in sensitization to
eggplant by SPT.When the study population was stratified
into four age groups (5–15, 16–30, 31–45 and 46–60
years), significant differences were observed between age
groups (Po0.05) for the prevalence of eggplant allergy
based on SPT with EE, and the prevalence was 2.8%, 7.5%,
Table 1. Subject demographic characteristics
n
Age Gender Dwelling
Mean?SD
35.6?17.0
34.6?16.4
39.2?18.9
Male (%) Female (%)Rural (%) Urban (%)
Total
Non-atopic subjects
Atopic subjects
741
586
155
386 (52.2)
304 (51.9)
82 (52.9)
355 (47.8)
282 (48.1)
73 (47.1)
304 (41.1)
252 (43.1)
61 (39.4)
437 (58.9)
334 (56.9)
94 (60.6)
Table 2. Analysis of adverse reactions to eggplant based on the organ system affected
Organ system affected
Number of subjects with
positive history (%)
Number of subjects affected by
each organ system
n.a.?
(a) Only C: 30
(b) C1other organ system: 10
(a) Only R: 13
(b) R1other organ system: 7
(a) Only GI: 8
(b) GI1other organ system: 2
(a) Only P: 1
(b) P1other organ system: 6
(a) Only O: 0
(b) O1other organ system: 6
Specific symptoms (number of subjects)
n.a.?
Skin rashes and itching all over the body (15)
and localized (25)
Wheezing (17), allergic rhinitis (3)
Any of the organ system affected
Cutaneous (C)
68 (100)
40 (58.8)
Respiratory (R) 20 (29.4)
Gastro-intestinal (GI) 10 (14.7)Gastric-reflux/cramping/bloating (9) and diarrhea (1)
Pharyngeal (P) 7 (10.3)Throat itching (6) and swelling (1)
Ocular (O)6 (8.8) Eye itching (4), reddening and oedema (2)
?n.a., not applicable.
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd, Clinical and Experimental Allergy, 38:1795–1802
Prevalence of eggplant allergy 1797

Page 4

7.8% and 4.9% in the aforementioned age groups, respec-
tively. Sensitization to eggplant by SPT was significantly
higher among atopic (16.7%) compared with non-atopic
(3.8%) subjects screened for eggplant allergy (Po0.01).
This difference between atopic and non-atopic subjects
was more pronounced in the age groups 16–30 years
(34.5% vs. 4.4%) and 31–45 years (22.7% vs. 3.4%), as
shown in Fig. 1 (panel a). Striking differences were also
observed between children and adults (2.8% vs. 6.9%) in
sensitization to eggplant by SPT. However, this difference
was statistically non-significant.
On analysis of the gender distribution, it was noted that
sensitization to eggplant was significantly higher in
females (Po0.05) despite the gender distribution in the
sample being nearly equal. It was observed that females
were twice as likely to be sensitized to eggplant as males
(2:1). This difference was further amplified in the 16–30
years age group (Fig. 1, panel b), wherein females were
four times as likely to be sensitized to eggplant as males
(4:1).
Further, when the study population was analysed for
differences in the SPT reaction between EE and EC, there
was a significant (Po0.01) reduction in the number of
SPT-positive subjects with EC (Fig. 2, panel a). Twenty-
one (2.8% of 741 subjects tested) out of 48 EE-positive
subjects have shownpositive SPT withEC. When the study
population was stratified into four age groups (5–15,
16–30, 31–45 and 46–60 years), the prevalence of egg-
plant allergy based on SPT with only EC was 2.7%, 4.8%,
2.1% and 1% in the aforementioned age groups, respec-
tively. There was a 56% reduction in the number of
subjects SPT positive to EC compared with that to EE
(Fig. 2, panel a). A similar trend was observed in male
(Po0.01) and female (Po0.05) subjects, when the genders
were analysed separately (Fig. 2, panel b). In case of
females, there was ?42% reduction in the number of SPT
positives to EC compared with that to EE, while it was
?82% in case of males. When the SPT differences were
analysed among the four age groups between EE and EC,
there was significant reduction in the number of SPT-
positive subjects with EC in the age groups 16–30 years
(38%, Po0.05), 31–45 years (73%, Po0.01) and 46–60
years (80%, Po0.01) compared with EE (Fig. 2, panel a).
However, the number of SPT-positive subjects in the age
group 5–15 years remained constant with both EE and EC.
Eggplant allergen-specific immunoglobulin E
When the allergen-specific IgE was analysed in the serum
samples of SPT-positive subjects, there was a significant
difference (Po0.01) in the A405 values (range: 0.184
–0.616) among the SPT-positive subjects. Six subjects
showed significantly higher A405values compared with
normal subjects (Po0.01), indicating the presence of
eggplant allergen-specific IgE (Fig. 3), which corresponds
Table 3. Analysis of adverse reactions to eggplant based on case history and skin prick test (SPT) results
Case history to
eggplant
SPT with eggplant
extract (EE)
Number of subjects,
n (%) Inference
1
1
1
?
?
?
1
?
1
?
68 (9.2)
32 (4.3)
36 (4.9)
16 (2.2)
657 (88.7)
Adverse reaction to ingestion of eggplant
Food allergy to eggplant
Food intolerance to eggplant
Asymptomatic sensitization (cross-reaction to other foods/pollens)
Normal subjects
0
10
20
30
40
5–15
(A: 22;
N: 50)
16–30
(A: 29;
N: 250)
31–45
(A: 44;
N: 147)
46–60
(A: 60;
N: 139)
Total
(A:155;
N: 586)
Age group (years)
Percent SPT positive
Atopic (A)
Non-atopic (N)
0
4
8
12
16
5–15
(M: 47;
F: 25)
16–30
(M:131;
F:148)
31–45
(M: 92;
F: 99)
46–60
(M:116;
F: 83)
Total
(M: 386;
F: 355)
Age group (years)
Percent SPT positive
Male (M)
Female (F)
1/1
4/17
6/9
6/4
17/31
**
*
**
**
**
(b)
(a)
Fig. 1. Prevalence of eggplant allergy based on positive skin prick test
(SPT) with eggplant extract (EE) between atopic and non-atopic subjects
in different age groups (panel a) and gender distribution within indivi-
dual age groups (panel b). Figures in parentheses indicate the number of
subjects tested in each category.?Po0.05;??Po0.01.
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd, Clinical and Experimental Allergy, 38:1795–1802
1798 B. N. Harish Babu et al

Page 5

to approximately 0.8% of the population screened for
eggplant allergy. Out of six subjects having eggplant
allergen-specific IgE, five (83.3%) subjects belonged
to the 16–30 years age group, and the remaining 1
(16.7%) to the 31–45 years age group. Further, the gender
distribution for eggplant allergen-specific IgE was 5:1
(female:male).
Association between case history, skin prick test and atopy
Among the 68 subjects with reported history of adverse
reactions to eggplant, 32 (47.1%) had positive prick test,
while the remaining 36 (52.9%) had a negative prick test
with EE. Of the 673 subjects without any clinical history,
16 (2.2%) had a positive prick test (Table 4). Among the
741 subjects, 155 (?21%) had reported history of atopy.
The association between atopy and positive prick with EE
was significant (Po0.05). Twenty-six (16.7%) out of 155
atopic subjects had shown positive prick, whereas 22
(3.8%) among the 586 subjects without clinical history of
atopy had shown positive SPT.
The predictive value of diagnostic SPT [19] for EE
was calculated and is shown in Table 4. It was observed
that the specificity and negative predictive value of SPT to
detect eggplant allergy were 97.6% and 93.5%, respec-
tively. However, the sensitivity of SPT to detect eggplant
allergy was 47% with a positive predictive value of
66.7%. The overall efficiency was 93%. Similarly, the
predictive value of diagnostic SPT for EC was calculated
(data not shown). It was observed that the specificity
and negative predictive value of SPT with EC to detect
eggplant allergy were 99% and 93%, respectively. But
the sensitivity of SPT to detect eggplant allergy
Age group (y)
*
*
**
**
**
**
**
eggplant extract (EE)
eggplant concentrate (EC)
eggplant extract (EE)
eggplant concentrate (EC)
5-15
(72)
16-30
(279)
31-45
(191)
46-60
(199)
Total
(741)
0
2
4
6
8
10
Percent SPT positive
0
2
4
6
8
10
Percent SPT positive
(a)
(b)
Female
(355)
Male
(386)
Total
(741)
Fig. 2. Comparison of prick-test positivity with the eggplant extracts (EE
and EC) in different age groups (panel a) and gender (panel b) (Po0.01
for stratification by age groups).?Po0.05;??Po0.01. Figures in
parentheses indicate the number of subjects tested in each age group.
0
0.2
0.4
0.6
0.8
06 12 1824 30 36 4248
SPT positive subject #
A405 (nm)
A1
A2 A3
A4
A5 A6
Wheal/flare
diameter (mm)
Subject
EE EC
A1 (F/45) 5.0/14
4.5/14
A2 (F/16) 5.0/16 4.5/16
A3 (M/24) 4.5/25 4.0/16
A4 (F/26) 5.0/25 4.5/14
A5 (F/27) 4.5/20 4.0/16
A6 (F/23) 5.5/16 5.0/14
Fig. 3. Detection of eggplant allergen-specific IgE among SPT-positive subjects by ELISA. The dashed line represents the A405value (0.191) of negative
control (pooled serum from five healthy non-atopic subjects). Serum was unavailable in the case of subjects no. 30 and 37. Inset shows the weal/flare
diameters of six SPT-positive subjects (labelled A1–A6) having significantly higher A405values than other atopic subjects with SPT positivity to
eggplant. Non-atopic subjects showed weal/flare diameters of 0–1/0 for both EE and EC.
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd, Clinical and Experimental Allergy, 38:1795–1802
Prevalence of eggplant allergy 1799

Page 6

was only 25% with a positive predictive value of 81%. The
overall efficiency, however, remained the same (92.5%).
Discussion
Studies on food allergy in Asia consist mainly of ques-
tionnaire surveys in individuals with atopic disease and
have seldom used specific IgE or confirmed the allergy by
food challenges. Although adverse reactions to ingestion
of eggplant have often been perceived in the Indian
population, there are no detailed studies regarding the
assessment of the prevalence of allergic reactions to
eggplant or other foods. Here, we have made an attempt
to assess the prevalence of eggplant allergy in relation to
age and gender, based on self-reported case history and
allergy diagnostic tests (SPT and eggplant allergen-speci-
fic IgE). Self-reported prevalence of food allergy varied
from 3% to 35% for any food in a meta-analysis study
reported recently [20].
The incidence of adverse reactions to eggplant based on
case history (9.2%) and SPT with EE (4.3%) is rather high
for any class of food in the general population; in the case
of eggplant, this could be due to the presence of endogen-
ous biological amines such as histamine (3.8mg), seroto-
nin (0.2mg), tryptamine (0.05–0.3mg) and tyramine
(0.3mg) per 100g eggplant (fresh weight) and some
secondary metabolites [15, 21, 22]. Adverse food reactions
can also be caused by pharmacological, metabolic, toxic
and idiosyncratic reactions. It is known that histamine-
containing foods such as cheese, vegetables (spinach,
eggplant and tomatoes), certain meats and red wines can
cause ‘dry’ flushes and produce histaminuria [21–23].
Therefore, it is highly likely that many subjects experience
non-IgE-mediated adverse food reactions to the ingestion
of eggplant. The most dominant clinical presentation of
eggplant allergy is cutaneous contrary to the oral allergy
syndrome (OAS), commonly seen with allergy to most
fruits and vegetables. This is possibly because eggplant
contains a wide spectrum (both proteins and non-protein
substances) of allergens [12–13, 15] and is consumed
almost always in cooked form as against most fruits and
vegetables that are consumed raw.
In this study, only few subjects (1.4%) experienced
adverse reactions within 30min to 2h of ingestion,
indicating the characteristic type I hypersensitivity.
Delayed reactions in majority of the subjects with a
positive history may often be due to mechanisms that are
non-IgE mediated or immune complex-mediated hyper-
sensitivities. The negative SPT/positive history in some
subjects is likely due to non-allergic food hypersensitivity.
The asymptomatic sensitization in few subjects could be
attributed to possible cross-reactivity between eggplant
and other food/non-food allergens [14, 24, 25], which
needs further evaluation to study whether it is a precursor
for clinical sensitivity and why in these patients, who may
have specific IgE, there are no clinical reactions.
The significant difference between age groups in the
prevalence of eggplant allergy with both EE and EC
indicates the possible influence of age on the skin prick
reactivity. More than 70% of the SPT-positive subjects
belonged to two age groups 16–30 and 31–45 years for
both EE and EC, clearly indicating that young adults and
middle-aged people (15–45 years of age) appear to be the
main risk group for eggplant allergy. This is also true
when the allergen-specific IgE to eggplant was considered
(16–30 years: five subjects; 31–45 years: one subject). This
interesting finding may be due to the fact that teens,
adolescents and middle-aged people probably are the
population groups most frequently consuming the offend-
ing food both at home as well as outside home. Our results
Table 4. Association between case history, skin prick reactivity to eggplant extract (EE) and history of atopy
History of adverse reaction to eggplant?
History of other atopy
PositiveNegativeTotal PositiveNegativeTotal
Positive prick 32 (47.1)w
TP
36 (52.9)
FN
68
16 (2.4)
FP
657 (97.6)
TN
673
48 (6.5)
TP+FP
693 (93.5)
FN1TN
741
26 (16.7)22 (3.8)48 (6.5)
Negative prick129 (83.3)564 (96.2) 693 (93.5)
Total155 586 741
?Number of subjects with: TP (true positive), correctly identified by a positive SPT to eggplant allergenic extract with a history of eggplant allergy; FP
(false positive), a positive SPT to eggplant allergenic extract without a history of eggplant allergy; FN (false negative), a negative SPT to eggplant
allergenic extract with a history of eggplant allergy; TN (true negative), a negative SPT to eggplant allergenic extract without a history of eggplant
allergy.
wPercentage values of SPT (positive or negative) are given in parentheses.
Diagnostic sensitivity (percentage positivity)=TP/(TP1FN)?100=47.1%.
Diagnostic specificity (percentage negativity)=TN/(TN1FP)?100=97.6%.
Positive predictive value=TP/(TP1FP)?100=66.7%.
Negative predictive value=TN/(TN1FN)?100=93.5%.
Efficiency=(TP1TN)/(TP1FP1FN1TN)?100=93.0%.
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd, Clinical and Experimental Allergy, 38:1795–1802
1800 B. N. Harish Babu et al

Page 7

with regard to distribution of age for eggplant allergy
have close resemblance to results from the Norwegian
register for food allergies [26].
The female-over-male dominance for sensitivity to
eggplant in the overall population (?2:1) and its
further amplification in the age group 16–30 years (4:1)
clearly show the increased skin reactivity of females to
EE, indicating the high prevalence of adverse reactions
to eggplant in adult females. The gender differences
were also observed when the allergen-specific IgE was
considered, wherein five out of six subjects having
specific IgE to eggplant were females. Virtually nothing
is known about the consumption behaviour of eggplant
among males and females. These gender differences are
strikingly similar to the reported cases of asthma, wheeze,
allergic rhinitis and other atopic conditions [27–29].
It is evident from the literature that food allergy is
more common among women, and that gender differences
are well known for allergic diseases [30, 31]. In general,
data from large epidemiological studies reported a male
predominance of asthma, allergic rhinitis, food allergy
and/or other atopic conditions before puberty, and a
female predominance after puberty [30–32]. A similar
trend was observed in the case of self-reported allergy to
peanut and tree nuts in the USA [33]. Studies suggest that
some female sex steroids are pro-inflammatory and in-
crease the susceptibility to atopy [34, 35]. Testosterone is a
powerful inhibitor of histamine and known to inhibit mast
cell degranulation, while estradiol is known to enhance
IgE-dependent mast cell activation [34, 35].
The reduction in the number of SPT positives with EC
compared with EE was quite significant between age
groups as well as genders. This reduction was more
evident with an increase in age and was more pronounced
in male subjects, as older age and male sex are associated
with higher skin prick response to histamine [36]. The
absence of histamine, secondary metabolites and low
molecular weight proteins of o12–14kDa in EC appears
to be a major cause for reduction in SPT response with EC.
Hence, there is a possibility of high proportion of false
positives in SPT with EE, which may lead to overestima-
tion of the incidence of eggplant allergy. The low mole-
cular weight allergenic proteins in plant foods generally
include lipid transfer protein, 2S albumin and profilin
[37]. The absence of allergen-specific IgE for eggplant in
many SPT-positive subjects could be attributed to (1)
down-regulation of the IgE immune response due to
prolonged avoidance of the offending food; (2) presence
of circulating immune complexes between food allergens
and allergen-specific IgE and also between allergen-
specific IgE and anti-IgE (normally of IgG and IgM
classes) and (3) the allergen in question being a low
molecular weight hydrophilic molecule incapable of
binding to ELISA plates [15, 38, 39], which may directly
and non-specifically activate mast cells.
Generally, food allergy tends to occur in subjects who
also have inhalant allergies, but it is not always so [40].
The association between positive history to eggplant and
SPT is found to be close to 50%, and that between history
of atopy and SPT is 16.7%; these atopic subjects reported
experiencing aggravation of their atopic condition fol-
lowing the ingestion of eggplant. The low association
could possibly be due to non-IgE-mediated mechanisms
or food intolerance mechanisms due to histamine and
other components in the eggplant causing non-specific
activation.
In spite of high specificity and negative predictive value
of SPT to detect eggplant allergy, the sensitivity of SPT to
detect eggplant allergy (with both EE and EC) was poor,
probably due to the fact that many of the clinical
symptoms reported with eggplant may not have been
related to type I hypersensitivity. It is apparent from these
results that SPT is not a good screening tool to identify
eggplant allergy, but would be very useful to rule out
eggplant allergy. Alternatively, EE prepared using ultra-
filtration to remove molecules o3kDa (such as histamine
and secondary metabolites) would be ideal for SPTs.
In conclusion, this study reveals that eggplant allergy
occurs in 0.8% of the population with a female predomi-
nance. The gender difference in sensitization to food
allergy to eggplant is interesting and a similar trend may
be observed for other foods in future. The identification
and further characterization of the IgE-binding compo-
nents in eggplant are being attempted with a view to
compare allergens from eggplant with other foods from
the Solanaceae family.
Acknowledgements
We thank Dr V. Prakash (Director, CFTRI, Mysore) for his
keen interest and constant encouragement. We acknowl-
edge the Department of Biotechnology (DBT), Govern-
ment of India, New Delhi, for a grant-in-aid project (No.
BT/PR6281/AGR/16/574/2005) to Y.P.V., and the Council
of Scientific and Industrial Research (CSIR), New Delhi, for
the award of a junior research fellowship to B.N.H. We also
thank Dr Lancy D’Souza, Professor of Psychology, Yuvar-
aja’s College, Mysore, for his valuable assistance rendered
in the statistical analysis.
References
1 Shek LP, Lee BW. Food allergy in Asia. Curr Opin Allergy Clin
Immunol 2006; 6:197–201.
2 Burks W, Ballmer-Weber BK. Food allergy. Mol Nutr Food Res
2006; 50:595–603.
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd, Clinical and Experimental Allergy, 38:1795–1802
Prevalence of eggplant allergy 1801

Page 8

3 Goh DLM, Chua KY, Chew FT et al. Immunochemical character-
ization of edible bird’s nest allergens. J Allergy Clin Immunol
2001; 107:1082–8.
4 Wieslander G, Norback D, Wang Z et al. Buckwheat allergy and
reports on asthma and atopic disorders in Taiyuan city, Northern
China. Asian Pac J Allergy Immunol 2000; 18:147–52.
5 Patil SP, Niphadkar PV, Bapat MM. Chickpea: a major food
allergen in the Indian subcontinent and its clinical and immu-
nochemical correlation. Ann Allergy Asthma Immunol 2001;
87:140–5.
6 Kumari D, Kumar R, Sridhara S, Arora N, Gaur SN, Singh BP.
Sensitization to blackgram in patients with bronchial asthma
and rhinitis: clinical evaluation and characterization of aller-
gens. Allergy 2006; 61:104–10.
7 Dhyani A, Arora N, Jain VK, Sridhara S, Singh BP. Immunoglo-
bulin E (IgE)-mediated cross-reactivity between mesquite pollen
proteins and lima bean, an edible legume. Clin Exp Immunol
2007; 149:517–24.
8 Asero R, Amato S, Alfieri B, Folloni S, Mistrello G. Rice: another
potential cause of food allergy in patients sensitized to lipid
transfer protein. Int Arch Allergy Immunol 2007; 143:69–74.
9 Kumar R, Srivastava P, Kumari D et al. Rice (Oryza sativa) allergy
in rhinitis and asthma patients: a clinico-immunological study.
Immunobiology 2007; 212:141–7.
10 Dalal I, Binson I, Reifen R et al. Food allergy is a matter of
geography after all: sesame as a major cause of severe IgE-
mediated food allergic reactions among infants and young
children in Israel. Allergy 2002; 57:362–5.
11 Allergome: a platform for allergen knowledge. Allergy Data
Laboratories s.c., Latina, Italy. www.allergome.org.
12 Pramod SN, Venkatesh YP. Allergy to eggplant (Solanum melon-
gena). J Allergy Clin Immunol 2004; 113:171–3.
13 Lee J, Cho YS, Park SY et al. Eggplant anaphylaxis in a
patient with latex allergy. J Allergy Clin Immunol 2004; 113:
995–6.
14 Gamboa PM, Sanchez-Monge R, Diaz-Perales A, Salcedo G,
Ansotegui J, Sanz ML. Latex-vegetable syndrome due to custard
apple and aubergine: new variations of the hevein symphony.
J Investig Allergol Clin Immunol 2005; 15:308–11.
15 Pramod SN, Venkatesh YP. Allergy to eggplant (Solanum melon-
gena) caused by a putative secondary metabolite. J Investig
Allergol Clin Immunol 2008; 18:59–62.
16 Lawande KF, Chavan JK. Eggplant (Brinjal). In: Salunkhe DK,
Kadam SS, eds. Handbook of vegetable science and technology:
production, composition, storage, and processing. New York:
Marcel Dekker, 1998; 225–44.
17 Patnaik N. Garden of life: an introduction to the healing plants of
India. New Delhi: Aquarian, an imprint of Harper Collins, 1993;
106–7.
18 Sanico AM, Bochner BS, Saini SS. Skin testing methods. In:
Adelman DC, Casale TB, Corren J, eds. Manual of allergy and
immunology, 4th Edn. Philadelphia: Lippincott Williams & Wilk-
ins, 2002; 485–6.
19 Hamilton RG, Adkinson NF Jr Clinical laboratory assessment of
IgE-dependent hypersensitivity. J Allergy Clin Immunol 2003;
111:S687–701.
20 Rona RJ, Keil T, Summers C et al. The prevalence of food allergy:
a meta-analysis. J Allergy Clin Immunol 2007; 120:638–46.
21 Udenfriend S, Lovenberg W, Sjoerdsma A. Physiologically active
amines in common fruits and vegetables. Arch Biochem Biophys
1959; 85:487–90.
22 Feldman JM. Histaminuria from histamine-rich foods. Arch
Intern Med 1983; 143:2099–102.
23 Maintz L, Novak N. Histamine and histamine intolerance. Am
J Clin Nutr 2007; 85:1185–96.
24 Jenkins JA, Griffith-Jones S, Shewry PR, Breiteneder H, Mills
ENC. Structural relatedness of plant food allergens with specific
reference to cross-reactive allergens: an in silico analysis.
J Allergy Clin Immunol 2005; 115:164–71.
25 Van Ree R. Clinical importance of cross-reactivity in food
allergy. Curr Opin Allergy Clin Immunol 2004; 4:235–40.
26 Lovik M, Namork E, Faeste C, Egaas E. The Norwegian national
reporting system and register of severe allergic reactions to food.
Nor Epidemiol 2004; 14:155–60.
27 Postma DS. Gender differences in asthma development and
progression. Gend Med 2007; 4 (Suppl. B):S133–46.
28 Almqvist C, Worm M, Leynaert B, for the working group of
GA2LEN WP 2.5 ‘Gender’. Impact of gender on asthma in child-
hood and adolescence: a GA2LEN review. Allergy 2008;
63:47–57.
29 Park MA, Matesic D, Markus PJ, Li JT. Female sex as risk factor
for penicillin allergy. Ann Allergy Asthma Immunol 2007;
99:54–8.
30 Jensen-Jarolim E, Untersmayr E. Gender-medicine aspects in
allergology. Allergy 2008; 63:610–5.
31 Marklund B, Ahlstedt S, Nordstr¨ om G. Health-related quality of
life among adolescents with allergy-like conditions – with
emphasis on food hypersensitivity. Health Qual Life Outcomes
2004; 2:65. [doi: 10.1186/1477-7525-2-65].
32 DunnGalvin A, Hourihane JO’B, Frewer L, Knibb RC, Oude
Elberink JNG, Klinge I. Incorporating a gender dimension in
food allergy research: a review. Allergy 2006; 61:1336–43.
33 Sicherer SH, Mu˜ noz-Furlong A, Sampson HA. Prevalence of
peanut and tree nut allergy in the United States determined by
means of a random digit dial telephone survey: a 5-year follow-
up study. J Allergy Clin Immunol 2003; 112:1203–7.
34 Osman M. Therapeutic implications of sex differences in asthma
and atopy. Arch Dis Child 2003; 88:587–90.
35 Zaitsu M, Narita SI, Lambert KC et al. Estradiol activates mast
cells via a non-genomic estrogen receptor-a and calcium influx.
Mol Immunol 2007; 44:1977–85.
36 Bordignon V, Burastero SE. Age, gender and reactivity to aller-
gens independently influence skin reactivity to histamine.
J Investig Allergol Clin Immunol 2006; 16:129–35.
37 Breiteneder H, Radauer C. A classification of plant food aller-
gens. J Allergy Clin Immunol 2004; 113:821–30.
38 Hegde VL, Mahesh PA, Venkatesh YP. Anaphylaxis caused by
mannitol in pomegranate (Punica granatum). Allergy Clin Im-
munol Int 2002; 14:37–9.
39 Hegde VL, Das JR, Venkatesh YP. Anaphylaxis caused by the
ingestion of cultivated mushroom (Agaricus bisporus): identifi-
cation of the allergen as mannitol. Allergol Int 2002; 51:121–9.
40 Emmett SE, Angus FJ, Fry JS, Lee PN. Perceived prevalence of
food allergy in Great Britain and its association with other atopic
conditions and with peanut allergy in other household members.
Allergy 1999; 54:380–5.
? c 2008 The Authors
Journal compilation? c 2008 Blackwell Publishing Ltd, Clinical and Experimental Allergy, 38:1795–1802
1802 B. N. Harish Babu et al