Diet and skin disease in dogs and cats.

Dietary factors have a major role in the maintenance of healthy coat and skin, and are significant in the etiology and therapy of certain skin diseases. Nutritional deficiencies are now uncommon as a result of the widespread feeding of complete and balanced pet foods. Deficiencies of (n-6) polyunsaturated fatty acids, zinc and vitamins, however, do arise in certain animal- or product-related instances. Supraphysiologic doses of vitamin A have been used in the management of vitamin A-responsive dermatosis in Cocker spaniels; other keratinization defects and seborrheic conditions may respond to retinoid therapy. Much interest has been paid to the therapeutic value of polyunsaturated fatty acid supplements in the management of dermatologic conditions associated with hypersensitivity reactions or keratinization defects. These studies have generally yielded disappointing results, which may reflect shortcomings in the design of some trials. Nevertheless, a placebo-controlled, double-blind, cross-over study has demonstrated a clear benefit of high dose (n-3) fatty acids in the management of pruritic skin disease. There is also preliminary experimental evidence that specific dietary (n-6):(n-3) fatty ratios are useful in the dietary management of inflammatory diseases. Although results of controlled clinical trials are awaited, the argument exists that it is the absolute amount of (n-3) fatty acid intake rather than ratio that is responsible for potential health benefits.