Ketotifen, benzocycloheptathiophene, (Zaditen) an orally active, anti-allergic and anti-asthmatic drug in a dose of 1 mg twice daily was given from 2 to 20 months in 20 selected patients with food allergy (FA) or food intolerance (FI). Sixteen children and four adults of which ten had atopic dermatitis (AD), six urticaria or/and angiooedema (two of which with oropharynx pruritus, oedema of the lips and anaphylactic shock), two asthma, and two gastrointestinal disorders. Food allergy was proved by clinical history, exclusion diet positive challenge test, skin prick tests (SPT) total IgE (PRIST) and specific IgE (RAST). Gastrointestinal permeability was measured in 5 out of 20 patients using mannitol and lactulose as probe molecules on three occasions: (1) by ingestion of the markers alone, (2) with concomitant ingestion of the offending food(s), and (3) with previous administration of ketotifen (2 mg) six hours before ingestion of markers and offending food. In all five individuals, food ingestion resulted in a significant rise of lactulose: mannitol urinary ratio and previous administration of ketotifen resulted in a normalization of the mannitol:lactulose urinary ratio. Patients with urticaria and/or angiooedema, gastrointestinal symptoms, asthma, and oropharynx pruritus with oedema of the lips were completely protected. In patients with AD, 70% were greatly improved or improved but 30% remained the same. It is our impression that ketotifen offers a new therapeutic dimension and therapy in FA.