Precipitating antibodies to foods have been assayed in three groups of patients with atopy. Forty-five per cent of patients with atopic eczema and IgE-mediated food allergy had precipitins to foods in their serum compared with only 15% of patients with atopic eczema without evidence of food allergy, and 16% of patients with atopic asthma and/or rhinitis. It is likely that this results from increased intestinal permeability in the group with eczema and food allergy.