The purpose of this study was to assess the frequency of reported food-induced symptoms, and of food allergy or intolerance in 169 allergic patients monosensitized to grass pollen and in a control group of 50 patients who were monosensitized to Dermatophagoides. This study clearly demonstrates that patients with grass pollen-allergic respiratory disease report adverse food reactions more frequently than patients allergic to Dermatophagoides. This increased incidence is due to a high percentage of adverse reactions to some vegetable foods, especially peanut, garlic, tomato, onion; and fruits, such as peach; and animal foods, such as egg (white) and pork. By separating the food-allergic patients from the food-intolerant patients, the number of subjects with food intolerance was higher than that of the patients with food allergy. Crossreactivity between pollen allergens and fruits and vegetable allergens may explain the association between pollen allergy and food allergy, but not the higher incidence of food intolerance. An increased intestinal permeability to macromolecules may be hypothesized as part of a primary defect in permeability in "atopic (pollen allergic?) constitution."