Food hypersensitivity in patients of Swedish allergy centers

Introduction: The lists of foods that cause hypersensitivity, varies between different countries and can also change with time because of changed eating habits. Our main goal was to find out which foods that, according to the views of the patients, cause hypersensitivity. We also wanted to compare the case histories of patients with the results of the skin tests with some common foods. Methods and patients: Consecutive patients, referred for allergy testing at the 4 clinics were asked: "Do you think that you have a hypersensitivity against foods?" Those answering "Yes" (n = 467, 310 women and 157 men) were asked to fill in a questionnaire in which 52 different foodstuffs were listed. For each of the foodstuffs, the patients were asked to answer if they regarded themselves having a sure or a probable hypersensitivity. Skin prick tests (SPT) were performed with standardized 10 HEP extract of birch, timothy and mugwort and with not standardized extract of wheat, cod, hazelnut and shrimp. Results: The foods that most frequently caused hypersensitivity were apple, kiwi, stone fruits (like plum, cherry and peach), peanut, orange, tomato and crustaceans. The majority of the patients reported a hypersensitivity against several foods (median 5) while only 20% had a monoallergy. The most common symptoms were oral allergy syndrome (OAS) (67%), skin symptoms (47%) and gastrointestinal symptoms (38%). The foods that most frequently caused OAS, were stone fruits, kiwi, carrot, hazelnut, banana, parsley and celery while orange, crustaceans, fish, chocolate, tomato and strawberry more often elicited skin symptoms. Milk, peas, bean, egg, poultry and spice often caused gastrointestinal symptoms. A significant correlation was found between positive SPT with birch pollen and hypersensitivity against apple, pear, hazelnut, kiwi, stone fruits, potato scarves and sunflower seed. A significant correlation was found, too, between positive SPT with mugwort and hypersensitivity against carrot, celery and parsley. The correlation between the case histories and the results of the SPT varied between the allergens. If the patients' histories were regarded as the true answer regarding clinical relevant hypersensitivity, the sensitivity of the SPT with hazelnut was 51%, with cod 23%, with wheat 9% and with shrimp 22%. The specificity of the SPT was with hazelnut 84%, with cod 98%, with wheat 89% and with shrimps 95%. If, however, the SPT was supposed to be the correct result, the sensitivity of the CH with hazelnut was 72%, with cod 65%, with wheat 6% and with shrimp 56%. The specificity of the case history was for hazelnut 68%, for cod 89%, for wheat 93% and for shrimp 80%. Conclusion: Vegetable food like nuts, apple, kiwi, peanut and stone fruits often cause food hypersensitivity in Sweden. The birch pollen allergy highly influence the pattern of the food hypersensitivity. In comparison with a similar investigation that was carried out 1973, hypersensitivity against kiwi and peanut is nowadays much more frequent. The correlation between the case histories and the results of the SPT is rather poor and varies between the allergens.