A Population Investigation of
Allergy Prevalence and
Cross- sensitization in
China
To the Editor,
Food allergy is a global public health problem, and its prevalence
continues to increase yearly[1]. According to
epidemiological data, up to 10% of the world’s population suffers from
food allergies[2]. Until now, there has identified
more than 200 kinds of food allergens, with varying prevalence rates by
specific food and population affected[3]. However,
geographical variability in the incidence, major food allergens, and
clinical presentation of food allergy as well as variations in symptoms
and clinical phenotypes due to race,dietary habit, age, and coexisting
allergic diseases exist[4]. The Codex Alimentarius
Commission has identified eight major food allergens, but their
prevalence trend in China is not clear. At present, some countries have
already established allergen lists according to their national
conditions [5]. However, national epidemiological
surveys of food allergy are limited in China, and the food allergen list
hasn’t been established yet. Therefore, we focused on the population of
32 different regions in China.The study collected 12,505 self-reported
data and 5360 clinical diagnosis data. Sample size stratified in 5
intervals (0-81 years old) was estimated. A questionnaire plus skin
prick tests (SPT) with food allergens were carried out. Descriptive
analysis and X2 test were made.
The result of our study showed that the proportion in the third age
interval (18-44 years old) accounted for the largest, peaking to 51%.
And the SPT positivity to egg and milk in the first and second age
interval (0-17 years old) decreased
over age while crustaceans became the first major allergen in the adult
group (≥18years old). No significant variation over gender was observed
in the skin test response to all kinds of foods. At the same time, the
prevalence of food allergens showed certain regional differences. For
example, the prevalence of insect allergy such as cicadas pupae in
Yunnan province was higher than that in other places. Most allergic
symptoms were mild. More than half of the allergic symptoms belonged to
Grade 1. Especially, Grade 3 symptoms were the highest in the egg,
accounting for 18% while Grade 4 symptoms were the most in the mango,
accounting for 1%. In addition, Grade 5 reaction (anaphylactic shock)
occurred in patients with crustaceans, milk, egg, peanut, and soybean
allergies while the soybean accounted for the highest proportion
(0.62%). The results of severe allergic reactions were consistent with
that of the WHO. Severe allergic reactions occurred in the milk, peanut,
crustacean, egg, and soybean allergies with the proportion increasing
successively. Of total population, the 56% was positive to only one
allergen, while 21% to two allergens, 11% to three allergens and 12%
to more than three allergens. Further analysis demonstrated that partial
cross-reactivity among the food involved. For example, beef - lamb, beef
- milk, beef - crustaceans, milk - lamb, milk - crustaceans, wheat -
buckwheat, peanut - soy, egg - milk, egg - wheat, egg - crustacean
allergies were all significantly associated. Expecially, we found that
cross-sensitization between egg and crustaceans.
In summary, with reference to the standards of WHO and FAO, we have
established a list of food allergens that is more suitable for the
actual situation in China. The top eight food allergens in China are
crustaceans, milk, egg, beef, peanut, soybean, mango, and mutton. Then,
we confired partial cross-sensitization among the food involved.