The cause of this group of diseases that affects cats, dogs, and horses is primarily an underlying hypersensitivity reaction. This is particularly true in cats and horses. Insect, environmental, and dietary hypersensitivities have been documented in cats, while insect hypersensitivity has been seen in some equine cases and in a smaller number of canine cases. Genetic predisposition and bacterial infections have also been noted as causes in cats. In all species, idiopathic cases exist.
Last full review/revision May 2013 by Stephen D. White, DVM, DACVD