Investigation on probable food allergy in undergraduates of a university in Guizhou Province

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(1.School of Public Health,Zunyi Medical University,Zunyi Guizhou 563099,China;2.Department of Dermatology,The second affiliated hospital of Zunyi Medical University,Zunyi Guizhou 563099,China;3.Department of Pediatrics,The second affiliated hospital of Zunyi Medical University,Zunyi Guizhou 563099,China)

[Abstract] Objective The purpose of this study was to conduct a survey among undergraduates of Zunyi Medical University to determine the prevalence of probable food allergy(FA) and common allergic foods.Methods A total of 1 800 questionnaires were distributed to freshmen of Zunyi Medical University.Participants with a convincing IgE mediated response to specific foods or a physician diagnosis were considered to have a probable FA.One year later,people with perceived FA were invited to conduct a second survey,and serum sIgE was tested.Results A total of 1719 questionnaires were returned,and 1453(84.5 %) people provided valid questionnaires.Prevalence of self-reported FA was 12.7 %(184/1 453),and prevalence of probable FA was 7.0 %(102/1 453).The common allergic foods were fruits(32.4 %,33/102),eggs(24.5 %,25/102),milk(21.6 %,22/102) and crab(17.6 %,18/102).In the second survey a year later,173 out of 184 people(94.0 %)provided valid questionnaires.The sIgE positive rate was 4.0 %(7/173),and 5.2 %(9/173) of respondents had food allergic reaction within a year,and there was no new FA case.Thus 1.1 %(16/1 453) of the students still has probable FA at present.The most common trigger food were shrimp(56.3 %,9/16),followed by crab(37.5 %,6/16) and eggs(31.3 %,5/16).Conclusions Lifetime probable FA rate among undergraduates at Zunyi Medical University is 7.0 %,and 1.1 % of the students still have probable FA at the second survey.The major trigger foods are shrimp,crab and eggs.

[Key words] food allergy; college students; survey; allergen sIgE

1 Introduction

Food allergy(FA) is defined as an adverse immune response to food proteins,leading to typical clinical symptoms mainly involving the skin,respiratory system and gastrointestinal system[1].For severe cases,shock and even death may occur.FA was reported to occur in 5 % of adults and 8 % of children,and once the allergenic food is identified,a strict avoidance diet is recommended[2].However,more than 90 % of FA reactions are caused by eggs,milk,peanuts,wheat,shellfish,soybeans,fish,and tree nuts,which are common daily foods and important ingredients for the food industry,thus an elimination diet is difficult to follow.Despite food allergen labeling legislation,there are still high frequencies of FA reactions due to accidental exposure[3].To make it worse,the reported prevalence of FA has been on the rise in the recent last decade.FA causes widespread concern around the world.

At present,most studies in this area focus on FA in children,while research on young adults is often ignored,and reports involving FA in undergraduates are even fewer.A large number of studies have shown that the prevalence of FA and the major offending foods are geographically different.China has nearly 20 % of the world’s population and its FA pattern was reported to be different from other countries[4].In 2018,there were more than 37 million college students in China.College students are a special group whose diet relies largely on food services,and collecting FA-related information is helpful to develop appropriate prevention and management strategies.However,to the best of our knowledge,FA research among college students in the country has been rare.This study aimed to investigate the prevalence of FA and major allergenic foods among undergraduates of Zunyi Medical University in China.

2 Materials and Methods

2.1 Selection of Study Population The inclusion criteria of the survey were as follows:first-year student of Zunyi Medical University with long-term residence in Guizhou Province,Non-freshmen students and those who lived outside of Guizhou Province for more than a year were excluded.

2.2 Survey Method Survey for lifetime FA:A total of 1 800 questionnaires(21 majors) were distributed between classes to freshmen on the new campus of Zunyi Medical University(October of 2017)by cluster random sampling method.Three trained proctors were present in each class to provide necessaryinstructions.Before distributing the survey,students were informed of (1) the inclusion criteria of the survey;(2) this program would last for a whole year,during which students who have adverse reactions after food ingestion were welcome to contact us,where free diagnosis and expert instructions would be given;(3) at the end of the program(October of 2018),those who were likely to have FA would be invited for a second survey.

Survey for FA at present:At the end of the program(October of 2018),184 students with self-reported FA were contacted one by one for the survey of FA at present.Eleven of them refused to participate,and 173 valid questionnaires were collected,including 99 lifetime probable FA and 74 perceived FA but not lifetime probable FA.For the 99 lifetime probable FA,two conditions were considered probable FAs at present:1,those who ate the trigger food within a year and showed a convincing IgE mediated response; and 2,those who performed a strict elimination diet and then showed positive sIgE test result.For the 74 perceived FA but not lifetime probable FA,only those who ate the trigger food within a year and showed a convincing IgE mediated response were considered to be probable FA at present.

Blood sample collection and test:Among the 99 lifetime probable FA respondents,86 followed a strict elimination diet and we intended to test their sIgE.However,our partner hospital can only detect some trigger foods(including egg,milk,soybean,peanut,wheat,shrimp and crab),so we only performed sIgE testing on patients who reported allergies to the above 7 food sources.Their blood was collected,and then the sera were sent to the Third People’s Hospital of Chongqing for testing.The automatic in vitro allergy detection system Phadia 100 was used,and a quantitative method was used for serum-specific IgE detection.

A flowchart of current FA investigations is shown in Figure 1.

Figure 1 Flowchart of FA within a year

Each student provided written informed consent for the two surveys.This program was approved by the Ethics Committee of Zunyi Medical University,(2016)1-077.

2.3 Questionnaire A specially designed questionnaire adjusted on the basis of the EUROPREVAL survey for adults[5],approved for this project by Zunyi Medical University was used.The questionnaire for lifetime FA included relevant demographic information,common trigger foods,whether the FA was diagnosed by a physician,whether adverse reactions occurred within 2 h of ingestion and symptoms typical of FA.

The questionnaire for FA at present included more detailed information concerning whether the trigger foods were ingested within the past year,and symptoms typical for FA were listed.

2.4 Food Allergy Definitions In this study,two FA definitions were used basing on a similar definition previously established by Ben-shoshan et al[6].Perceived FA：All self-reported cases of food ingestion that followed by onset of FA symptoms.

Probable FA:all self-reported FA accompanied by either a convincing IgE mediated reaction or a physician diagnosis.

A convincing IgE mediated response to specific foods is defined as at least two mild signs/symptoms or one moderate to severe sign/symptom,which may be IgE mediated and occur within 120 min of ingestion.

2.5 Statistical analyses The data analysis was performed using SPSS statistics 18.0(SPSS Inc,Chicago,IL).The descriptive statistics for categorical variables are summarized as frequencies and percentages.A chi-squared test and Fisher’s exact test were used for categorical variables.All tests were 2-sided.P<0.05 was considered significant.

3 Results

3.1 Lifetime FA

3.1.1 Participation Rate A total of 1 719 returned questionnaires were collected,of which 266 questionnaires were not completed and were thus invalid.A total of 1 453(84.5 %) participants provided valid questionnaires,including 432 males and 1 021 females.

3.1.2 Prevalence of lifetime FA Of the 1 453 respondents,184(12.7 %) reported FA to at least one food(perceived FA).Thirty-two of the perceived FA students(17.4 %) reported that they had been diagnosed by a physician.Seventy of them had a convincing IgE-mediated response but did not consult a physician.Thus,102 students(102/1 453,7.0 %) were categorized as having a probable FA,including 24 males and 78 females.Table 1 summarizes the demographic characteristics of the respondents with lifetime probable FA.

Table 1 Demographic characteristic of the respondents

3.1.3 Trigger foods for lifetime probable FA Trigger foods for lifetime probable FA are shown in Figure 2.The most common trigger foods were fruits(33/102,32.4 %),eggs(25/102,24.5 %),milk(22/102,21.6 %),and crab(18/102,17.6 %).

Of the 102 people who had probable FA,65 people were allergic to one food and 37 people were allergic to two or more foods.

3.1.4 Symptoms for lifetime probable FA The distribution of specific symptoms is presented in Table 2.Dermatological symptoms were the most common complaints.

Table 2 Major symptoms for lifetime probable FA

3.2 FA at present For students who did not report FA,we provided them with our contact information and encouraged them to contact us in case of possible FA.However,no new cases were found.A total of 173 participants who had perceived lifetime FA returned valid questionnaires during the second survey,at a response rate of 94.0 %.Among them,9 ate allergenic food during the past year and developed allergic symptoms within 2 h of ingestion,and 7 showed positive results in the sIgE test.Therefore,16 of the students investigated were categorized as having probable FA at present,including 6 males and 10 females.

The trigger foods for probable FA at present are shown in Figure 2.The most common trigger food was shrimp(9/16,56.3 %),followed by crab(6/16,37.5 %) and eggs(5/16,31.3 %).Of the 16 students who had probable FA,7 were allergic to one food and 9 were allergic to two or more foods.Interestingly,the 3 students who were previously allergic to peanut no longer had probable peanut allergies.

Figure 2 Trigger food for lifetime probable FA

The specific symptoms for probable FA at present are shown in Table 3.Dermatological symptoms were the most common complaints.

Table 3 Major symptoms for probable FA at present

4 Discussion

College students spend most of their time on campus and commonly have meals in the canteen.To meet the demands for the majority,dishes with allergic ingredients such as eggs,fish,and soybean are present,which may easily be eaten by mistake by FA patients.On the other hand,young people become independent and are unsupervised during their college years.They are responsible for their own health and are able to decide which foods to eat.Many research findings indicate that severe FA reactions and even FA-induced death occur in universities[7-8].Thus,research on FA among university students is important for comprehensive support measures.In this work,we collected information on both lifetime FA and FA at present.To reduce recall bias,the survey for FA at present was conducted one year later.

In this study,the total incidence of reported FA was 12.7 %,which is similar to that found by surveys conducted in some other countries,e.g.,Kuwait University students have a self-reported FA rate of 12.0 %,and Dutch adults have a self-reported FA rate of 12.1 %[9-10].The rate of self-reported FA is approximately twice as high as probable FA(7.0 %),a proportion similar to that found in an FA survey conducted among US adults[11].The prevalence disparity between perceived FA and probable FA may indicate that many students with self-reported FA actually have no immunological or clinical evidence of real IgE-mediated FA[9].However,they can still be annoyed by other types of FA,such as non-IgE mediated or mixed FA.

This study showed that the most common allergenic foods for lifetime probable FA were fruits(32.4 %),eggs(24.5 %),milk(21.6 %),and crab(17.6 %).

Fruits,at the top of the trigger food list,might cross-react with pollen,wheat,shellfish,and crustaceans[12-14].The high frequencies of egg and milk allergies may be due to lifetime FA counts,and more FA cases occur during childhood.There are numerous reports that eggs and milk are the major allergenic foods for children[15-16].On the other hand,the survey for FA at present indicated that the main trigger foods are shrimp,crab,and eggs.The most common trigger foods are different from those found in studies conducted in other countries.Among American adults,the most common FAs are induced by shellfish,milk,and peanuts[11,17].For European countries,foods that induce adult allergies are commonly hazelnut,peach,apple,shellfish,and fish[18].Among Iranian adults,the most common allergenic foods are sesame seeds,eggs and milk[19].Common allergenic foods are different among countries and regions,which may be related to geographical environment,lifestyle and ethnic factors[20].Studies have shown that seafood is the leading cause of FA in the Asia-Pacific region,which may be related to this region having the highest consumption of seafood in the world[21].

Compared with lifetime FA,the number of people with FA at present was lower,especially for those with eggs and milk allergies.This is in accordance with other investigations,pointing out that more than half of children outgrow egg/milk allergies[22].And three students who had peanut allergies outgrew the allergy.It was reported that approximately 20 % of peanut allergy patients outgrow the allergy[23].Because there are only 3 peanut allergy cases,limited by the number of patients,it is not clear whether more people outgrow peanut allergies in China or it is just a coincidence.

One limitation of this study is that,not all allergenic foods could be tested by the hospital during the sIgE testing step.This is a common problem for all hospitals because companies refuse to produce allergens that affect only a small portion of the population.Another limitation is that we used a survey that covered a long time range for lifetime FA,which may have led to memory bias.Despite these limitations,we performed a survey one year later,thus more accurate data were collected for FA at present.

5 Conclusion

FA reduces the quality of life of patients and is a very serious food safety problem.FA prevalence among university students in China is not low,and this situation calls for strengthening school education and prevention and emergency measures.