Food allergy and chronic urticaria: the value and limits of in vitro testing for IgE antibodies specific for food allergens

Objective: The intent of this study is to evaluate chronic urticaria patients in view of the observation that multiple food allergies could be a causative factor. The CAP Radioallergosorbent (RAST) Fluoroimmunoassay (FEIA) test will be utilized for measuring specific IgE antibodies. The value, interpretation and limits of the test, being a new sensitive assay, will be evaluated. Design: Patients suffering from chronic urticaria, who gave clinical history suspecting foods as causing their complaints, were selected, for this investigation. Subjects: The study included 112 patients suffering from chronic urticaria. The sex distribution was 61 female and 51 male. Their ages ranged between 19 to 65 years. Serum samples were obtained and tested against the suspected food allergens. These included 16 foods which consited of egg (white), egg (yolk), milk, fish, meat, peanut, wheat, tomato, strawberry, cacao, chicken meat, shrimp, cheese, yeast, banana and orange. Results: Specific IgE antibodies, to one or more food, were detected in 42 (37.5%) of the patients. These included reactions in all CAP PAST classes, class 1 to class 4. Out of these, only six patients (5.4%) showed multiple food allergies with significant CAP PAST values. These were further evaluated for possible food allergy. Conclusion: Detection of IgE antibodies, specific for food allergens, is worthwhile in chronic urticaria patients who suspect foods as causing their complaints. As the assay is sensitive, results should be interpreted carefully. Because the test is expensive and the yield is low, the panel of food allergens, selected for testing, should be limited to the minimum possible number.