food allergy is an increasing problem worldwide , affecting about 6% of children and 2% of adults ( 1 ) . the prevalence of food allergy as well as other allergic diseases has risen in the last few decades ( 2 ) . allergen avoidance is one of key components in the management of allergies ( 3 ) . recognition of common food allergens in each geographical region is valuable for physicians to be able to remove only culprit allergens from the diet for a limited period of time . in the united states , the most common food allergens are cow s milk and eggs , while the most common allergens in europe and middle east countries are fruits and eggs , respectively ( 15 ) . the most common food allergens among iranian children with allergy ( asthma , allergic rhinitis , atopic dermatitis , and urticaria ) that were established with the prick test , were milk , eggs , and wheat flour , respectively ( 6 ) . furthermore , the most current cause of anaphylaxis in iranian children was food ( 89.7% ) , with milk and wheat being the most common ( 7 ) . because , anaphylaxis is a life - threatening condition , identifying foods that cause this condition is very important ( 8) . true identification and elimination of foods responsible for food allergy are better management approaches for food hypersensitivity reactions . complete avoidance of common foods ( egg , wheat , milk , soy , fish , and peanuta ) is not possible . skin prick tests ( spt ) are useful for demonstrating the foods responsible for ige - mediated reactions , but there are no definite laboratory studies to help identify cell - mediated responses ( 3 , 4 ) . elimination diets followed by food challenges can determine the foods responsible for cell - mediated food allergies ( 9 ) . the purpose of this study was to determine the most common food allergens in children with various allergic symptoms , including atopic dermatitis , allergic rhinitis , asthma , anaphylaxis , and digestive problems in mashhad , iran . in iran , we need further studies that demonstrate the overall prevalence of food allergies and the rate of hospital admissions for food - induced anaphylaxis - the most severe expression of food allergy . three hundred and seventy - one patients with cutaneous ( atopic dermatitis and urticaria ) , respiratory ( asthma and allergic rhinitis ) or gastrointestinal ( diarrhea , vomiting , colitis ) manifestations , who were referred to the pediatric allergy and gastroenterology clinics affiliated with mashhad university of medical sciences from september 2012 to august 2014 were investigated for food allergies . for ige - mediated disorders , the allergy skin prick test ( spt ) and for cell - mediated disorders exclusion diets , food challenge , and endoscopic examination were performed in addition to spt . we also scaled up the results to give the estimated number of patients with recorded diagnoses of food allergies in iran . this study was approved by human ethics protocols with informed written consent from each patient ( 4 ) . also , the study was approved by the ethics committee of the medical school at the mashhad university of medical sciences . all patients underwent routine allergy diagnosis tests , including clinical history , physical examination , and the skin prick test ( spt ) . the skin prick test was done based on standard procedures , using purified allergen extracts with negative and positive controls being normal saline and histamine , respectively ( l0 mg / ml ) , as mentioned above . the extracts were placed on the volar surface of the forearm and subsequently introduced into the epidermis using a disposable hypodermic needle . data were excluded if the wheal reaction of negative control ( saline ) was larger than 2 mm and the wheal reaction of positive control ( histamine ) was less than 3 mm . a reaction was considered positive if the resulting wheal was at least 3 mm larger than the negative control . the results were analyzed by spss version 17 ( new york , ny , usa ) , and statistical analysis was done with the chi - squared test and t - test . the values of the quantitative variables were checked by the kolmogorov - smirnov test for normal distribution . results with normal distribution were analyzed by parametric anova or student s t - test . non - parametric mann - whitney and kruskal - wallis tests also were used for assessment of results with non - normal distributions . three hundred and seventy - one patients with cutaneous ( atopic dermatitis and urticaria ) , respiratory ( asthma and allergic rhinitis ) or gastrointestinal ( diarrhea , vomiting , colitis ) manifestations , who were referred to the pediatric allergy and gastroenterology clinics affiliated with mashhad university of medical sciences from september 2012 to august 2014 were investigated for food allergies . for ige - mediated disorders , the allergy skin prick test ( spt ) and for cell - mediated disorders exclusion diets , food challenge , and endoscopic examination were performed in addition to spt . we also scaled up the results to give the estimated number of patients with recorded diagnoses of food allergies in iran . this study was approved by human ethics protocols with informed written consent from each patient ( 4 ) . also , the study was approved by the ethics committee of the medical school at the mashhad university of medical sciences . all patients underwent routine allergy diagnosis tests , including clinical history , physical examination , and the skin prick test ( spt ) . the skin prick test was done based on standard procedures , using purified allergen extracts with negative and positive controls being normal saline and histamine , respectively ( l0 mg / ml ) , as mentioned above . the extracts were placed on the volar surface of the forearm and subsequently introduced into the epidermis using a disposable hypodermic needle . data were excluded if the wheal reaction of negative control ( saline ) was larger than 2 mm and the wheal reaction of positive control ( histamine ) was less than 3 mm . a reaction was considered positive if the resulting wheal was at least 3 mm larger than the negative control . the results were analyzed by spss version 17 ( new york , ny , usa ) , and statistical analysis was done with the chi - squared test and t - test . the values of the quantitative variables were checked by the kolmogorov - smirnov test for normal distribution . results with normal distribution were analyzed by parametric anova or student s t - test . non - parametric mann - whitney and kruskal - wallis tests also were used for assessment of results with non - normal distributions . this study was performed on 371 patients 53.9% of whom were males and 46.1% were females . patients younger than 2 accounted for 35.8% of the patients , while 34.6% were 2 to 7 , 22.7% were 8 to 12 , and 6.9% were 1318 . the most common presenting symptoms in our patients were allergic rhinitis ( 45% ) , asthma ( 32% ) , atopic dermatitis ( 30% ) , colitis ( 17.5% ) , and urticaria ( 8.3% ) . the presenting symptoms with lower incidence were anaphylaxis ( 2% ) , gerd ( 2% ) , and recurrent infection ( 0.5% ) . in all studied patients , the most common foods responsible for food allergy were egg white ( 17.8% ) , pepper ( 15.8% ) , curry ( 14.3% ) , egg yolk ( 14% ) , cow s milk ( 10% ) , and tomato ( 7.8% ) . the less common food allergens in our study were cocoa ( 5% ) , orange ( 4.7% ) , peanut ( 4% ) , banana ( 4% ) , cereals ( 4% ) , soya ( 3.7% ) , grape ( 3.7% ) , almond ( 3.5% ) , wheat ( 3% ) , fish ( 2.8% ) , sesame ( 1.5% ) , and meat ( 0.7% ) . in our study , egg white , egg yolk , and cow s milk were the most common food allergens in patients younger than 2 and , as the child aged , the allergies were mostly outgrown and their frequency decreased . in patients older than 2 , pepper and curry were the most common food allergens ( table 1 ) . in this study we realized that the most common food allergens in patients with respiratory symptoms were pepper and curry , in patients with gastrointestinal manifestations , it was cow s milk , and in patients with skin problems , they were egg white and egg yolk ( table 2 ) . this study demonstrated that the most common food allergens in 371 patients who were referred to pediatric allergy clinics in mashhad were egg white , pepper , curry , egg yolk , cow s milk , and tomato . however , other studies in another countries and in another geographical region in iran had different results . in our study in mashhad , the most common food allergen was egg white with the highest frequency among the children younger than 2 ( 48.1% ) . in research that was done by pourpak in tehran , cow s milk was the most common food allergen in almost all cases for children less than one year old ( 10 ) . in contrast , mukoyama identified egg , cow s milk , and wheat as the top three food allergens among children under the age of six in japan . he reported that , when the child grows up , this list was changed to fish , shrimp , and black wheat ( 11 ) . alvarado discovered that fruits ( 54.2% ) , nuts ( 20% ) , and fish ( 14.35% ) were the most common food allergens in spanish children ( 12 ) . marrugo concurred with alvarado in sensitization rate for fruits with 14.9% as the main trigger , but he ranked marine food and meat as the second and third most - common food allergens in colombia ( 13 ) . rivas partially concurred with us , as egg was his top allergen in children under five years of age . ( ours was egg white . ) yet , his findings were compatible with marrugo , ranking fruits and nuts at the top in the population older than five ( 14 ) . al - hammadi also indicated that egg , fruits , and fish were the three top allergens in asian children based on his findings . this list was followed by peanut , nuts , cow s milk , wheat , and vegetables ( 15 ) . however , kavaliunas blamed fruits , marine food , and milk ( and dairy products ) for the advent of food allergy in european children , in agreement with alvarado and marrugo s top allergy triggers ( 16 ) . our second most - common food allergen was pepper , with 43 children between 2 to18 years old affected . pourpak found that tomato ( 36 children with 28.1% between 6 and 12 years old ) , egg white ( 28 children with 37.5% < 1 year old ) , and egg yolk ( 24 children with 33.3% < 1 year old ) were placed in declining order of second , third , and fourth common food allergens ( 10 ) . the foods responsible for food allergy are different in the various countries because of the probable role of genetic , cultural , and nutritional factors . compatible with another studies , the children outgrew their sensitivity to egg white , egg yolk , and cow s milk , while these are the most food allergens in children younger than 2 . after children are 2 years old , the frequency of allergy to pepper , curry , cacao , and tomato increases slowly . these results occurred because , often , food allergies are not manifested to egg and milk until after 5 years of age ( 3 ) . in this study , the most common food allergens in this group were curry , pepper , tomato , cacao , orange , and grape . in these patients , we know that cross reaction between allergen of salsola kali ( profiling ) and fruit proteins in grape and melon , many children with this allergy show oral allergy syndrome after eating these fruits ( 17,18 ) . oral allergy syndrome is an ige - mediated hypersensitivity that usually is confined to the oropharynx and consist of the rapid onset of oral pruritus , tingling of the lips , tongue , palate , and throat . symptoms are generally short lived ( 3 ) . in 3040% of children with moderate to severe atopic dermatitis , food allergies occur . the skin prick test can help us to determine which food was responsible , and this test was sensitive , cheap , and available . among our patients , 30% came with atopic dermatitis , and , in them , the most common food allergens were egg white , egg yolk , cow s milk , pepper , and tomato . this result is appropriate to other studies that were done in the past , such as in the study of salehi in which the most common food allergens in children with atopic dermatitis were egg ( 39.22% ) in < 2 years old , cow s milk ( 35.13% ) and egg ( 32.43% ) in children who were 2 to 6 years old , and peanut ( 25% ) and egg ( 16.67% ) in children older than 6 years old . therefore , the prevalence of egg allergy is highly significant in patients with atopic dermatitis in salehi s research in tehran ( 19 ) . bergmann shows cow s milk , hen s egg , peanut , wheat , soy , nuts , and fish are responsible for > 90% of food allergies in children with atopic dermatitis ( 20 ) . in kim s research , the most common foods causing food hypersensitivity were egg and milk in patients with atopic dermatitis in korea ( 21 ) . kwon confirmed the most - common food allergens in atopic dermatitis patients were egg and milk ( 22 ) . gastrointestinal manifestations in our patients were colitis , abdominal pain , early satiety , and poor weight gain . in our study , the most common food allergens in patients with gastrointestinal manifestations were cow s milk , egg white , egg yolk , pepper , curry , cereals , and banana . in the last studies , sensitivity to cow s milk was the most common cause of food allergy in young infants , but it also has been associated with hypersensitivity to soya , egg , wheat , rice , chicken , and fish in older children ( 3 ) . cell - mediated hypersensitivities predominate ( e.g. gastrointestinal problems ) , making the standard prick skin test of little diagnostic value ; therefore , challenge tests should be done to determine the foods responsible for these symptoms . the prevalence of culprit foods that produce food allergies depends of several factors , including age , presenting manifestation , and where the patient lives . since many food allergies are outgrown , patients should be reevaluated regularly to determine whether they have lost their reactivity to specific food allergens . future studies must be designed rigorously using standardized methodology , including dbpcfc , to limit the potential sources of bias that could weaken the estimates of food allergies , and more high - quality studies are needed in other regions of iran so that the results can be compared .
introductionfood allergy is an increasing problem worldwide , but the foods responsible for food allergy are not the same in different countries , probably because of the role of genetic , cultural , and nutritional factors . 
 the aim of this study was to determine the common food allergens in pediatric patients with different presentation of food allergy.methodsin this cross - sectional study , all of the patients were referred to pediatric allergy clinics affiliated with mashhad university of medical sciences from september 2012 to august 2014 . for patients with ige - mediated food allergy that was diagnosed with clinical manifestations , the skin prick test was done . 
 the results were analyzed by spss version 17 and statistical analysis was done with the chi - squared test and the t - test . 
 p values < 0.05 were considered statistically significant.resultsthree hundred seventy - one patients ( 53.9% male , 46.1% female ) with ages in the range of three months to 18 years were studied . 
 the most frequent food allergen in all patients with decreasing prevalence were egg white ( 17.8% ) , pepper ( 15.8% ) , curry ( 14.3% ) , egg yolk ( 14% ) , cow s milk ( 10% ) , and tomato ( 7.8% ) . 
 the most common presenting symptoms were respiratory ( allergic rhinitis 45% , asthma 32% ) , dermatologic ( atopic dermatitis 30% , urticaria 8.3% ) , colitis ( 17.5% ) , and gasteroesophagial reflux disease ( gerd ) ( 2% ) . according to the prevalence of food allergens in different age groups 
 , we realized that , after the age of three years , the frequency of sensitization to egg white , egg yolk , cow s milk , wheat and cereals was decreased and allergy to pepper and curry was increased.conclusionthe prevalence of culprit foods that produce food allergies depends on several factors , including age , presenting manifestation , and where the patient lives . 
 as many food allergies are outgrown , patients should be reevaluated regularly to determine whether they have lost their reactivity or not .