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. In 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 reaction; 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.

Immunologic cross-reactivity among cereal grains and grasses in children with food hypersensitivity.

BACKGROUND: Because of a lack of clinical data from food challenges, allergists often recommend dietary restriction of all cereal grains in patients with sensitivity to at least one grain. OBJECTIVES: The purposes of this study were to assess the degree of intrabotanical cross-reactivity among cereal grains and related grasses, to better define the prevalence of multiple grain hypersensitivity, and to define the protein fractions associated with wheat hypersensitivity. METHODS: One hundred forty-five patients evaluated by food challenges and skin prick tests were divided into three groups: group 1, cereal grain and grass allergies; group 2, wheat allergy alone; and group 3, grass allergy alone. Fifteen patients were further selected from groups 1 to 3. Sodium dodecylsulfate--polyacrylamide gel electrophoresis and immunoblot analyses were performed on six grains and four related grasses with sera from these patients. RESULTS: Only 21% of patients had symptomatic reactivity as determined by food challenge; 80% had reactivity to only one grain. As determined by immunoblot analyses, patients in groups 1 and 2 showed extensive cross-reactivity (within each group) among grains but little cross-reactivity among grasses, whereas patients in group 3 showed cross-reactivity between the grains and grasses. Patients with wheat allergy had specific IgE binding to wheat fractions 47 kd and 20 kd, bands not recognized by patients with grass allergy. CONCLUSIONS: Clinically insignificant cross-reactivity exists among cereal grains and grasses; therefore, elimination of all grains from the diet of a patient with grain allergy is unwarranted. Further purification and characterization of the 47 kd and 20 kd wheat fractions is needed to provide more specific in vitro testing.

Soy sensitivity: personal observation on 71 children with food intolerance.

The controversies on the use of soy milk as a substitute in cow's milk intolerance prompted us to study: the incidence of soy sensitivity in a pediatric population (71 children, mean age 5.9 years, 45 boys and 26 girls) with food intolerance: the influence of a prior soy milk feeding on soy sensitivity: the relationship between soy, cow's milk and seed allergy. The patients were subdivided in two groups, one of atopic patients (50 subjects, 28 of which previously fed soy) and the other of non atopic patients (21 subjects, 12 of which previously fed soy). In the atopic group prick and RAST gave positive results to soy in 46% of case, with no difference between subjects fed soy and not. There was a relationship between any and peanut RAST in 82%; between soy and pea in 70%; between soy and cow's milk in 27% of cases. Soy milk challenge was positive in 10 out of 58 children (6 atopic and 4 non atopic); 4 our of 21 atopic patients with a cow's milk intolerance had a positive soy milk challenge: 3 of 10 non atopic patients with cow's milk intolerance were reactive to soy too. 77% of atopic and 90% of non atopic children were responsive both to seeds and soy. It can be concluded that soy sensitivity is rather rare in patients with food intolerance (17.2% of cases) and is not correlated with cow's milk intolerance while is significantly correlated with seeds allergy; there is no difference between atopic and non atopic subjects and between patients previously fed soy and never fed soy.