Objects: The aim of this study was to investigate in adult asthmatics, which kinds of food allergen can cause a positive reaction by skin scratch test and cause symptoms when administered as a food challenge.
Subjects and method: Three thousand one hundred and two adult asthmatic patients were submitted to skin scratch tests with housedust mite. Japanese cedar extracts and 33 types of food. Sixty one adult asthmatic patients with a history of immediate, adverse reactions after food ingestion underwent open food challenge.
Result: Six hundred and twenty five of 3102 subjects (20.1%) had a positive test to one or more food allergens. The commonest food allergens were shrimp (27.7%), crab (27.7%), yeast (23.8%) and buckwheat (15.8%). The positive tests of shrimp, egg and cow's milk were highest in patients under 20 years and decreased with age, however the test rates of crab and soybean were not influenced by age. Positive food challenge responses occurred in 30/60 subjects (50%). The foods, which most of ten provoked a reaction, were buckwheat, shrimp, crab and bread.
Conclusion: Skin scratch test results in adult asthmatics were different from those in atopic children where the commonest foods with positive tests were egg, cow's milk and soybean. Except for patients with a previous life-threatening reaction. Food allergy should be diagnosed by food challenge where a patient's history of adverse reaction to food, positive skin test and RAST strongly support specific food reactivity.