An apparently gluten-induced photosensitivity in horses

Primary photosensitization was observed in 3 Appaloosa mares, The skin lesi ons were diffuse erythema followed by edema and subsequently weeping and fi nally dry gangrene and ulceration. The severe photosensitivity dermatitis w as apparently induced by gluten ingestion. Resolution of lesions occurred a fter withdrawal of the suspected dairy concentrate feed and prevention of e xposure to sunlight. Neither the ponies nor donkey, which were not fed with the suspected concentrate, exhibited similar skin lesions;or other clinica l abnormalities. Gluten metabolites may contain photodynamic agents that ca use photosensitization in horses.