BACKGROUND Adverse food reactions are not uncommon among children. Several of these reactions are IgE-mediated. Prevalence of adverse food reactions among Thai children has not been fully explored. OBJECTIVE The objectives of the study are (1) to determine prevalence of adverse food reactions and food allergy among Thai children, (2) to determine types of foods producing such reactions, (3) to study clinical manifestations of these reactions, and (4) to study various risk factors relating to food adverse reactions among these children. METHODS A total of 656 Thai children were surveyed (188 subjects between 6 months to 3 years of age and 468 subjects between 3 to 6 years of age). The study was a cross-sectional study. Parents answered food allergy questionnaire. Families with children reporting adverse food reactions were invited to participate in further investigation for food allergy with skin prick testings and food challenges. RESULTS Forty-one of 656 children (6.25%) were reported to experience prior food reactions by questionnaire survey. Common foods reported to be the cause of reactions among younger children were cow's milk and eggs whereas seafood, particularly shrimp, was the most commonly reported food for older children. Three of 21 children underwent food challenge had positive challenges. Skin prick tests to incriminated food were all positive in these three children. Significant risk factors for developing adverse food reactions among these children were personal allergic history (OR = 4.89, CI 2.2-10.75) and family history of allergy (OR = 2.87, CI 1.42-5.89). CONCLUSIONS Prevalence of adverse food reactions using food allergy questionnaire was 6.25%. From a limited number of those with positive food challenges, prevalence of IgE-mediated food allergy among this group of Thai children is estimated to be 0.45% (CI 0.01-0.8%).