Soy allergy in atopic children

Background: Although soy is considered a major food allergen (along with milk, egg, peanut, fish, and wheat), the prevalence of soy allergy in the pediatric population is not well defined. Objective: To determine the prevalence of soy allergy in atopic children attending the Allergy Clinic at the Pediatric Department of Milan University. Methods: Seven hundred four patients with allergic signs and symptoms, aged 1 month to 18 years, were recruited between December, 1991 and April, 1992. The subjects with positive skin prick tests to soy were tested using a DBPCFC with powdered soy formula in fruit juice, and rice or corn flour as placebo. Ln children who refused the liquid challenge, capsules containing dehydrated soy flour or talcum powder as placebo were administered. An age-matched and sex-matched group of subjects with negative skin prick tests to soy were tested using an open challenge with soy formula. Results: A positive skin prick test to soy was found in 148/704 patients (21%); 131 out of 148 children with positive skin prick test (group A) and 131 out of 556 children with negative skin prick test to soy (group B) were challenged with soy: 8/131 (6%) in group A had a positive soy challenge while no clinical reactions were observed in children in group B. A younger median age, a positive past and current personal history of cow milk allergy, and a previous history of soy allergy were found most often in children with positive soy skin prick test and positive soy challenge than in children with positive skin prick test and negative soy challenge. The eight soy-allergic children reacted to the soy challenge mostly with cutaneous and gastrointestinal symptoms; symptoms were immediate in six and late in two children. The eliciting dose of soy was very small in the immediate reactions; higher and repeated doses were necessary for the onset of late reactions. Conclusion: The prevalence of clinical soy allergy in our children with positive skin prick tests to soy is 6.1% (8/131), while none of 131 children with negative skin prick test to soy reacted to the challenge.