Food allergy is an adverse immune response reaction to food and estimated to affect nearly 3-8% of children in America [1,2,3]. In Korea, the prevalence of food allergy in children aged 6-12 years was estimated at 10.9% in 1995, 8.9% in 2000 and 12.6% in 2012, according to a survey from the Korean version of International Study of Asthma and Allergy in Childhood (ISAAC) [4,5]. In 2005, a survey of children living in Seoul showed that 11.7% experienced a food-related allergic reaction more than once [6]. Treatment for food allergies is avoidance of allergenicrelated foods and epinephrine auto-injector (EPI) for accidental allergic reactions [7].

Food allergy presents a variety of symptoms on the skin (urticaria, dermatitis, eczema, angioedema, itching) and in the gastrointestinal tract (nausea, vomiting, diarrhea, abdominal cramping) and respiratory tract (rhinitis, asthma, laryngeal edema) [8]. Food-induced anaphylactic shock is the most frightening symptom that is acute in onset, occurring within minutes or hours, and may lead to death if prompt treatment is not administered [9]. Major food allergens among children are eggs, cow's milk, fish and other seafood, while peanuts, tree nuts, fish and crustaceans (shrimp, crab, lobster) are common among adults [8,10].

A survey of 993 children aged 18 and younger who visited 7 hospitals in the Seoul and Gyeonggi area showed that eggs, cow's milk and dairy products, peach, shrimp, pork, peanuts and tree nuts were common allergenic foods [11]. Lee et al. [5] studied the prevalence of food allergies and perception of food allergen labeling in school foodservice for 27,679 students at 1,000 elementary, middle and high schools in Korea. Approximately 12.6% of students showed food-related allergies, and 6.8% of respondents had been diagnosed with food allergies by a doctor. Cow's milk, peach and crab were the most common allergy-related foods among first and fifth graders.

A series of nationwide cross-sectional questionnaire surveys of Korean children in 1995, 2000 and 2010 showed that the prevalence of food allergies in children has increased [4,5]. The Ministry of Education implemented a mandatory 'school lunch food allergen labeling system' in 2012 that requires disclosure of allergenic food ingredients in school meals and developed 'the manual for school lunch food allergen labeling' [12,13]. In the United States, food allergy guidelines have been published by the American Academy of Allergy, Asthma, and Immunology and the American Academy of Pediatrics [14,15,16]. School management guidelines for food allergies detail preventive measures, such as a food allergen avoidance diet, substitution diet, food allergy education that includes avoidance of food sharing and cross-contact, and epinephrine for acute food reactions [17]. Based on guidelines and preventive measures, the role of parents, dietitians and teachers is important in the care and protection of children with food allergies [17]. Further, the education and management of young students with food allergies is important because mostly spend time at school [18] and lack awareness of food allergies and the ability to handle them [19].

Previous studies reported on the prevalence of food allergies and causative foods. However, little has been done to identify differences in perception level of food allergy labeling and knowledge of food allergies and dietary practices among groups with and without food allergy experience. The aims of this study were to investigate food allergens and symptoms of food allergy, and to examine knowledge of food allergies, recognition of food allergy labeling, and good dietary practices by elementary school children in fourth, fifth and sixth grade with and without food allergies.

This study investigated food allergens and food allergy symptoms of fourth, fifth and sixth grade elementary school students, and examined food allergy-related knowledge and perception of food allergen labeling.

Our results showed that the prevalence of food allergy among respondents was 19.7%, and the most common food allergy-related symptoms were urticaria (26.7%), itching (22.1%), vomiting (11.6%), others (8.1%) and nausea (4.7%). Lee et al. [5] reported a food allergy prevalence of 12.6% (27 of 679) among students in Korea and 6.8% of these had been diagnosed with a food allergy by doctors. Our result (19.7%) was higher than the other study (12.6%) and national surveys (9-11%) [4,5]. This may be explained by the self-administered questionnaire for children, not have diagnosed a doctor. Subjects may have confused food allergy with other adverse reactions such as foodborne disease, lactose intolerance or food additive hypersensitivity.

The mostly common allergenic foods in this study were cow's milk and shrimp (7.0%), eggs and mackerel (5.8%), peanuts and tomato (3.5%), wheat and crab (2.3%) and pork, peach, and soybean (1.2%). Cow's milk, eggs, soy and peanuts are foods known to trigger allergies frequently among children [4], though an allergy to cow's milk or eggs is usually subside after childhood or adolescence [26]. A study on the prevalence and main characteristics of food allergenic school children in France reported that 62 of 182 respondents (25.4%) outgrew food allergies. Children most outgrew a food allergy to cow's milk (55.2%), but never to tree nuts [27]. Peanut and seafood allergies are most common among adults in North America, and a buckwheat allergy is common among adults in Japan and Korea [28,29,30]. The prevalence of food allergy to specific foods may be affected by age, ethnicity and eating habits [4,8].

Our study reported a number of allergenic foods outside the 12 designated by the Ministry of Food and Drug Safety (MFDS) [31], including cheese, cucumber, kiwi, melon, clams, green tea, walnuts, grape, apricot and pineapple. Currently, there are more than 160 allergenic foods worldwide. The 'school lunch food allergen labeling system' has been implemented by the Ministry of Education since 2013, and uses a red color and number from 1-12 for designated food allergens to indicate their presence on foodservice menus [13,32]. A study on management of food allergies in school lunch programs reported that 75% of most frequently served school meals contained more than one food allergen among 890 menu items [33]. Chicken, mushroom, kiwi and clams triggered food allergies, in addition to the 12 most common food allergens. Different varieties of food allergens have been reported [34,35,36], and specific food allergens such as tree nuts can seriously impact Korean children [36,37]. However, food allergens not designated by the MFDS are not managed or disclosed in school lunch programs [18]. Kim et al. [33] found that 84% of 154 participating schools tend to assign complete responsibility to food-allergic children and their caregivers. Therefore, "allergenic food labeling" should be improved, and policy makers from the Ministry of Education need to consider food allergies outside the 12 common food allergens. All allergenic foods should be managed with the same care as any food item can cause an allergic reaction in children.

Healthy dietary life practices between the two groups were not significantly different, except 'drink two cups of milk.' This result may be explained by the need to restrict or avoid allergenic foods or potential food allergens such as milk, fish, eggs and meat among children with food allergies. A study suggested that allergy subjects were prone to lifestyle choices such as more frequent alcohol drinking and smoking than non-allergy subjects. [23] The allergy group had dietary habits of skipping breakfast more often, higher consumption of instant foods and less fruit, and more irregular eating patterns, in addition to more frequent consumption of pork, eggs, walnuts, tuna, kiwi and shellfish than non-allergy counterparts [23].

To the best of our knowledge, prevalence of food allergy in childhood and type of food allergens for a representative sample of Korean children has not yet been investigated. Therefore, longitudinal studies and the establishment of a surveillance monitoring center for food allergy incidents are needed for accurate data on prevalence of food-allergic children and all causative food allergens.

On perception of food allergen labeling on school meals, results showed that respondents viewed it as important but were not satisfied. Data showed that differences between students with and without food allergy experience were rarely significant. However, Lee et al. [5] found that food-allergenic students read labeling more carefully and frequently on school menus than students without food allergies. Lee et al. [11] studied the perception of allergenic food labels among 962 subjects that included 337 food-allergic subjects and 656 non-food allergic subjects. The survey found that 38.3% of food-allergic and 18.6% of non-food allergic subjects understood allergy-related labels and 79.2% of food-allergic and 70.1% of non-food allergic subjects expressed a negative view on the current food allergen labeling system. Reasons for dissatisfaction were too ambiguous, ingredient list too technical, font size too small, and hard to understand food allergen labels. Rhim and McMorris [38] found that only 21% of school staff could read hidden allergens on food labels. Sicherer et al. [39] reported that 55% of peanut-allergic children accidentally ingested them at school due to allergens hidden in food, food-sharing and cross-contact. Food-allergic consumers or those buying for individuals with a food allergy urgently need to read and easily understand food allergy-related labels. Convenient and clear labeling of food allergens and identification of possible crosscontamination with allergenic ingredients is needed to make informed and safe food choices. Adding more food allergens to the list of 12 statutory food allergens requiring mandatory ingredient labeling must also be considered, as management guidelines of food allergen labeling state that the system is provided to help food allergic consumers.

On food allergy-related knowledge, children knew the definition of food allergy, food allergens, and the difference between a food allergy and foodborne disease, but were not informed about mechanisms of food allergies or anaphylaxis. For prevention and treatment of food-allergic incidents among children, schools need to provide education on food allergy, preventive measures and treatment guidelines. In America, most schools provide special meals on request and food substitution for foodallergy students [38]. Food allergy education should contain easily understood contents and a class teaching real-life skills, such as how to read a food label or shop for safe ingredients. A comprehensive educational program with the cooperation of parents, school teachers and dietitians for food allergic children can prevent and manage serious consequences of food-allergic reactions in children.

The study had limitations. First, the study was a case study with the upper grade students at an elementary school, which must be considered when generalizing the results. Second, knowledge of food allergies did not show a significant difference between students with and without food allergy experience, except one question. Therefore, future study is needed to identify the association between food allergy and the learning capacity of students. Third, the prevalence of food allergy among students was totally dependent on the self-evaluation of respondents. Students with food allergy symptoms were not asked if a doctor diagnosed a food allergy, which may explain our data showing a somewhat higher prevalence rate than other studies. A future study should include a survey question on diagnosis of food allergies by a doctor.

This study suggested meaningful outcomes in that additional allergenic foods should be designated to ensure safe food-service and school administrators should advocate for a better allergy labeling system to inform and protect students. Future studies can use information about prevalence and types of food allergy among Korean children to develop effective educational programs and implement preventive measures on food-related allergies.