Prevalence of Food Allergy in Taiwan: A Questionnaire-based
Tzee-Chung Wu1,2, Tzu-Chun Tsai2,3, Ching-Feng Huang4,5, Fang-Yuan Chang1,
Chih-Chung Lin6, I-Fei Huang7, Chia-Hsiang Chu8, Beng-Huat Lau9, Lite Wu1,
Ho-Jen Peng3, Ren-Bin Tang1,2.
1Children’s Medical Center, Taipei Veterans General Hospital; 2 School of Medicine,
National Yang-Ming University; 3 Department of Medical Research and Education,
National Yang-Ming University Hospital;4 Department of Medical Research and
Education, Taipei Veterans General Hospital; 5Graduate Institute of Medical Sciences,
National Defense Medical Center; 6Department of Pediatrics, Taichung Veterans
General Hospital; 7Department of Pediatrics, Kaohsiung Veterans General Hospital;
8Department of Pediatrics, Hualien Tzu-Chi General Hospital; 9 Department of
Pediatric, Shin-Kong Memorial Hospital;
RUNNING TITILE: food allergy in Taiwan
Dr. Tzee-Chung Wu
Children’s Medical Center, Taipei Veterans General Hospital, Taipei, Taiwan, R.O.C.
Address: 201, Sec. 2, Shih-Pai Road, Taipei, Taiwan 11217, R.O.C.
FINANCIAL SUPPORT: grants by Department of Health, Executive Yuan, R.O.C.,
Taiwan. (doh grant 94-stu-02 & 95-stu-02)
This is an Accepted Article that has been peer-reviewed and approved for publication
in the Internal Medicine Journal, but has yet to undergo copyediting and proof
correction. Please cite this article as an “Accepted Article”; doi:
Aim: Food allergy is common in children and adults, and could be potentially fatal in
minor group. It's important for physicians to identify the prevalence of food allergies
and to recognize common food allergens to make precise diagnosis and choose correct
Methods: We used a nationwide, cross-sectional, random questionnaire-based survey
to estimate the self-reported and expert-screened prevalence of food allergies and to
identify the common food allergens in Taiwan. In this study, the perceptional
diagnosis of food allergies was screened by physicians according to descriptions of
convincing symptoms and medical recordings, in the meantime non-allergic adverse
reactions to foods including food intolerance or food avoidance were clarified.
Results: A total of 30,018 individuals who met the inclusion criteria were evaluated,
and 6.95% of them were diagnosed as victims of food allergies. The prevalence was
3.44% in children under 3 years of age, 7.65% in children aged 4-18 years and 6.40%
in adults, respectively. About 77.33% of the food allergy population had experienced
recurrent allergic attacks. Systemic reactions happened about 4.89% in food allergies
group. The most commonly reported food allergen in Taiwan is seafood, including
shrimp, crab, fish and mollusk. In addition, mango, milk, peanuts and eggs were also
important food allergens in general population; while milk, shellfish, peanuts, and
eggs were common in children.
Conclusions: Less than 10% of the Taiwan population suffers from food allergy with
different allergic symptoms to variable food allergens in different age groups.
KEY WORDS: food allergy, questionnaire survey, prevalence, food allergen,
Food allergy encompasses a range of disorders caused by adverse immune
responses to dietary antigens. It affects all age groups and is increasingly encountered
in daily life, especially among children. It is similar to other atopic disorders such as
asthma, allergic rhinitis, and atopic dermatitis.
The prevalence of food allergy has dramatically increased in recent years but
there are few longitudinal studies [1-6]. Exposure to allergens may result in a broad
spectrum of symptoms ranging from minor discomfort to cardiopulmonary
compromise and potentially fatal episodes. Food allergy is recognized as a major
problem in Westernised countries and is a leading cause of anaphylaxis treated in
emergency departments in a number of countries . Thus, the imperative for
clinicians to understand the prevalence of food allergies and recognize common food
allergens in their own regions cannot be overemphasized. Reports on the prevalence
of food allergies or adverse reactions to food in Asia are limited and epidemiologic
studies on food allergies in the general population or among children are very few in
The aim of this study was to assess the prevalence of self-reported and
expert-screened food allergy in an unselected population of children and adults in
Taiwan. Common food allergens were also identified and allergic symptoms in
different age groups were classified.
PATIENTS AND METHODS
Study design and population
A nationwide, cross-sectional, random, questionnaire-based survey was
performed from April 1 to October 31, 2004. Pre-school children were recruited from
six out-patient departments in northern, middle, southern, and eastern Taiwan as they
were brought for routine health examination. School-age children and adolescents
were randomly enrolled from 35 schools selected from each stratum of Taiwan, which
was designated according to particular ethnic and geographical characteristics of
residents using the probabilities proportional to sizes method similar to the research
design of the “Nutrition and Health Survey of Taiwan Elementary School Children
(2001-2002)” . Adult subjects were also randomly selected from each stratum.
The six experts who participated in this study were experienced pediatricians
from six medical centers located in the northern, middle, southern, and eastern Taiwan
and were experts in either gastroenterology or immunology. They reviewed all of the
questionnaires and cases with equivocal statements or vague descriptions were
excluded. They also analyzed the descriptions of symptoms and records of physicians’
evaluations to distinguish food allergy from non-immunologic adverse food reactions
. The subjects’ medical records were thoroughly reviewed for data such as the
duration between intake and symptoms, and the amount of ingested food. Briefly,
cases diagnosed by clinicians and confirmed by positive laboratory tests, including
serum IgE, eosinophil count, MAST/CAPS, skin prick test, food challenge test, or
tissue biopsy were enrolled as definite cases. On the other hand, cases that tended to
be diagnosed as food intolerance (i.e., lactose intolerance), food avoidance, and
reactions to food contaminants, additives, toxins, or infections were excluded. If the
symptoms occurred within minutes, the diagnosis was presumed to be food allergy on
the basis of type I immediate hypersensitivity reaction. Non-allergic food
hypersensitivity was usually characterized by a delayed reaction, occurring hours or
even days after eating certain food. Allergic reactions did not depend on the amount
of ingested food, whereas food intolerance worsened as more food was consumed.
The Institutional Review Committee of Taiwan’s Veterans General Hospital
approved the study. All of the participants or their parents provided informed consent.
A standard, anonymous questionnaire was designed to obtain personal history
and general information, including feeding history, dietary habits (e.g., vegetarian),
and co-existing atopic disorders. The self-administered questionnaire was given to
each subject to answer. If a subject answered “Yes” to the question “Has your
child/have you ever had an allergic reaction to food?”, then the respondent moved on
to the other questions related to specifically identifying the possible foods, clinical
symptoms, types of treatments, and laboratory results. A panel of common foods,
including those previously published [8,9] and additional food with local importance,
was listed for assessment with multiple options. In cases of positive allergic reaction
to food, detailed descriptions, including the age of the first attack, clinical
manifestations, duration of symptoms, number of episodes of food allergy, medical
assessment including treatments, and allergy tests were all obtained.
Data management was performed using the SAS statistical software for Windows.
Significance level was set at p<0.05 for all of the tests.
From the 38,926 questionnaires distributed, 30,280 (77.8%) were completed.
After review and interpretation by the expert physicians, 262 ineligible cases were
excluded. A total of 30,018 cases, including 14,899 males and 15,119 females (sex
ratio M/F 0.99), were valid for further analysis. There were 813 children aged less
than 3 years, 15,169 aged between 4-18 years, and 14,036 aged more than 19 years.
Of the 30,018 cases, 2086 (6.9%) were confirmed by the experts to have a food
allergy . The percentage of food allergy was 3.4%, 7.7%, and 6.4%, respectively in
the different age groups. Of the food allergy groups, 77.3% experienced more than
one episode of food allergy (Table 1).
Types of allergic foods
Food frequently reported in previous studies and in the literature [8,9] were
included in the questionnaire. Food items listed in Table 2 were the most common
causes of food allergies in Taiwan. Milk was one of the most important food allergens
in toddlers; 32.1% (9 in 28 sensitized children) of children younger than 3 years of
age with a food allergy had a milk allergy. As age increased, the major food allergen
shifted from milk to seafood, including shrimp and crab, and some exotic fruit. In
addition to the listed food, ”other” types of food included orange, almond, corn, and
Clinical presentations of food allergies
Based on the severity of food-associated adverse reactions, 95.1% of subjects
suffered from mild irritating symptoms without life-threatening events (Table 3).
However, about one in every 714 patients with food allergy might suffer from
cardiovascular collapse, with high morbidity and mortality (Table 3).
In this study, seafood, especially shrimp and crab, is the most common cause of
severe food allergic reactions, while egg, milk, and peanut are less important. (Fig. 1).
Three cases had anaphylactic reactions, including cardiopulmonary collapse. Two of
them were sensitized to shrimp while the other had a peanut allergy.
Clinical presentations of mild food allergy were grouped into three categories:
oro-gastrointestinal symptoms, rhino-respiratory symptoms, and dermatologic
symptoms. Table 4 shows the frequency of these symptoms in the different age groups.
Even though the allergic reaction occurred after food was ingested orally,
oro-gastrointestinal symptoms did not dominate.
To date, this cross-sectional study is the first nationwide questionnaire survey in
an unselected population to assess the prevalence of food allergy in Taiwan. This
study not only has a large sample size but also has a high return rate. The lifetime
self-reported and expert-screened prevalence is around 6.9% in this study, which is
less than those of similar studies in other countries. In the 1990s, the self-reported
food allergy prevalence in the United Kingdom, Holland, and the United States was
14.7%, 12.4%, and 16.6%, respectively [11-13]. The Woods’ study in 2001 that
analyzed incidences across several countries had an average incidence of 12.2%,
ranging from the lowest, 4.6% in Spain to the highest, 19.1% in Australia. It also
reported that people experienced illness following ingestion of particular food,
presumably due to food allergy or intolerance . A 2007 meta-analysis on food
allergies in communities revealed a self-reported prevalence of 3-35% .
The prevalence and incidence of food allergies also varies immensely according
to the diagnostic criteria used. In Germany, Zuberbier reported a population-based
study with an incidence of self-reported adverse reactions to food ranging from 35%
to 3.6% in the same groups using double-blind, placebo-controlled food challenge
(DBPCFC) . Other results all showed that self-perceived food allergy/intolerance
is higher than the point prevalence, which can be detected by objective assessments,
including skin prick test (SPT), IgE titer, or DBPCFC. Though further tests were not
performed in the present study, the prevalence of food allergies was still lower than
those of other similar reports based on questionnaires in western countries. This result
may reflect the special characteristic of food allergy in Taiwan, or even in Asia. Some
claim that cultural differences and the consumption of certain dietary types may
contribute to the difference between countries . Although there are few studies in
Asian countries , food allergy in Asia may be quite unique due to the different
cultures and eating habits, which may result in occurrence of unique food allergens
. Moreover, the screening by physicians in the present study may contribute to the
elimination of some equivocal responders, making the diagnosis more reliable and
Food allergy is more common in children and is increasing. Twenty years ago,
the prevalence rate in children aged less than 4 years estimated by a US study was 6%
. Without significant differences, the prevalence was about 5-6% in children in the
first three years of life in the UK between 2001 and 2002 by a cohort study . The
self-reported prevalence in school-age children was 6.7% and 7.2% in France and the
Netherlands, respectively [19-20]. A 2005 cross-sectional study via questionnaire
survey in Thailand reported that 6.25% of children had prior food reactions . The
prevalence of parent-reported adverse food reaction was 8.1% in Hong Kong
pre-school children , and about 10.9% of elementary school children experienced
allergic symptoms to foods in a nationwide questionnaire survey in Korea . In the
present study, 7.4% of children aged less than 18 years had experienced food allergy,
which was similar to data of most Western countries.
The availability of various foodstuffs and change in dietary habits may play
important roles in the increasing prevalence in Asian communities. Nevertheless, the
results of questionnaire studies should be interpreted with caution. For example, as to
the first question of the questionnaire “has your child or have you ever had an allergic
reaction to food”, our study revealed that the adult group displayed a definitely lower
prevalence than the younger aged groups (4-18 years old) while the culmulative
prevalence used to relatively rise as age and exposure time increase. This
phenomenon points to a typical recovery tendency of some food allergies, such as
milk or egg allergies, which resolve with time. Meanwhile, the effect of generational
difference also complicate with this phenomenon. That is, younger patients have
higher risk of morbidity from food allergy because modern-day children are exposed
earlier to various exotic foods. There are some studies indeed disclosed that the
prevalence of food allergy is known to be lower in adults than children, implying that
the prevalence of food allergy in children is increasing during these decades [24, 25].
According to a meta-analysis in 2007, the self-reported prevalence rate of food
allergy varies from 1.2-17% for milk, 0.2-7% for egg, 0-2% for peanut and fish,
0-10% for shellfish, and 3-35% for other foods . Shellfish, which was reportedly a
less common food allergen than egg, milk, and peanut a decade ago in Asia ,
recently became a major sensitizing food source in the region . The present study
confirms this; our data reveals that the most common food allergen is seafood,
including shrimp, crab, mollusk, and fish. This may be due to the large consumption
of seafood in Taiwan, which is a sea island.
In pediatric groups, cow’s milk and eggs are reported to be the most common
causes of allergic reactions in younger children and seafood, particularly shrimp, in
older children. This is reported in Thailand , Singapore , and Hong Kong .
The spectrum of food allergens in this Asian study is a little different from the
prevalent food among Caucasians. For example, tomatoes and hen’s eggs are the most
common encountered allergens in a study in Turkey, while chocolate, apple, and
hazelnut are the prominent foods reported as ” ill or trouble” in some European
countries [14,16]. There are some distinctive food allergens in certain areas. Mango, a
Southeast Asian fruit, is the fourth most common food allergen in Taiwan in this study,
while sesame is quite common in countries in the Middle East . It can be
concluded that food allergens are influenced by dietary habits, which are usually
influenced by geographic factors and living environment.
In the general population, allergic rhinitis is the most common self-reported
allergic symptom, with 23.4% lifetime prevalence, followed by urticaria and allergic
asthma with a total of 9.4% lifetime prevalence . The present study discloses that
the common symptoms of food allergic reactions are rhino-respiratory symptoms and
skin manifestations, with prevalence of 58.6% and 27%, respectively. In younger
children, the most common manifestation is urticaria. As they grow older,
rhino-respiratory symptoms become more prominent. Oral-gastrointestinal symptoms
are relatively less important in this study, although foods are ingested orally and
contact the gastrointestinal mucosa.
Anaphylactic shock, the most severe complication of food allergy, accounts for
0.14% of allergic reactions in this survey, similar to the 0.19% in Young’s study,
wherein 4 anaphylaxis cases occurred in 2152 patients . Other studies reveal
higher incidences of anaphylactic shock due to food in the pediatric group, about
4.9% in France and 5.3% in Hong Kong. These studies conclude that anaphylactic
shock caused by food allergy occurs more frequently in adults than in children
[30-33], which is not corroborated by data in the present study.
In summary, the self-reported and expert-screened prevalence of food allergy in
the general population of Taiwan is 6.9%. Shrimp, crab, fish, mango, mollusk, and
milk are the main types of food associated with adverse allergic reactions. Peanut or
tree nut allergies are not as common in Taiwan as they are in Western countries.
Although positive cases may be indicative of IgE-mediated food allergy, the true
prevalence of food allergy should be further assessed by double-blinded,
placebo-controlled food challenge (DBPCFC), which is considered the gold standard
for allergy testing.
This study was supported in part by grants (DOH Grants 94-stu-02 and 95-stu-02)
from the Department of Health, Executive Yuan, R.O.C., Taiwan.
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