An enzyme-linked immunosorbent assay was developed for quantifying feline serum allergen-specific IgG directed against selected house dust, pollen and flea allergens. The assay was used to compare allergen-specific IgG concentrations in sera from healthy cats, cats with non-dermatologic illness, confirmed allergic cats and undiagnosed pruritic cats. Our results demonstrate that cats with confirmed allergic skin disease have significantly more IgG directed against house dust, flea and ryegrass allergens than other cat groups examined. These results support the theory that cats with allergic skin disease have an underlying TH2 lymphocyte response that directs production of both allergen-specific IgG and IgE.