Clinical Update on Feline Allergic Dermatitis

The terms allergic dermatitis and hypersensitivity dermatitis (HD), comprising food hypersensitivity (food HD), flea HD and nonflea/ nonfood HD (“atopic dermatitis”), are used interchangeably for this syndrome. it is now preferred to stop using the term atopic dermatitis or atopy in cats as presence of antigen-specific igE, with possibly exclusion of flea-specific igE, cannot be linked to clinical signs of feline allergic dermati- tis. in contrast, serum levels of allergen-specific igE correlate with age, outdoor life style, absence of deworming, and absence of flea control measures (1).
Pruritus is the hallmark clinical symptom in cats with allergic dermatitis but the clinical presentation of the skin lesions varies and comprises miliary dermatitis, head-and neck dermatitis, self-induced alopecia, and eosinophilic dermatitis (e.g. eosinophilic plaque). recent studies have investigated first whether certain clinical signs are characteristic for certain subgroups of feline allergic skin disease (nonflea/ nonfood HD, flea bite HD and food HD) and secondly if diagnostic criteria could be established for diagnosis of these diseases similar to the diagnostic criteria for atopic dermatitis in dogs (2,3).
In the first study around 500 pruritic cats were enrolled and the following diagnoses were made: flea HD (29%), food HD (12%), nonfood/ nonflea HD (29%), other pruritic diseases (24%) (2). although the authors found some lesional distribution patterns more commonly in some subgroups none of these was pathognomonic. in cats with nonfood/ nonflea HD extremities and abdomen were more commonly involved. Cats with flea HD displayed more often lesions on the rump or tail, dorsum or flank area. a difference in clinical signs between food HD and nonflea/ nonfood HD could not be found.
In the second study, data were used only from cats in which a flea HD had been excluded and a mathematic approach was applied to develop a set of diagnostic criteria for diagnosis of nonflea/nonfood HD.3 When 6 out of a list of 10 criteria were fulfilled a sensitivity of 90% and a specificity of 83 % could be achieved. of note is however that selection of cats based on these criteria does not exclude food as a cause for the allergic disease (3). [...]