F LINE PRURITUS Amelia G. White, DVM, MS, DACVD
INTRODUCTION Allergies in cats are one of the most challenging and frustrating medical conditions we deal with as veterinarians. This is largely due to the severity of dermatological lesions, significantly decreased quality of life, limited medical therapy options and difficulty administering medications to cats. Cats tend to develop significant psychogenic components to pruritic behaviors that need to be addressed in order to maintain adequate control of the clinical signs.
Types of Allergy in Cats
There are several types of allergies in cats and the most common include flea bite hypersensitivity, mosquito bite hypersensitivity, atopic dermatitis and adverse food reaction (food allergy). Each of these conditions creates significant pruritus and dermatitis that Prominent lesions of the eosinophilic granuloma complex. Rodent ulcer on the upper lip. can lead to self-mutilation and severe secondary bacterial and Image courtesy of Dr. Amelia G. White. fungal skin infections. These allergies are not curable, but, with a thorough understanding of which allergies are problematic for the cat, they can be well-managed long term.
The Eosinophilic Granuloma Complex/ Syndrome
Cats are unique in that they tend to develop similar dermatological lesions despite a differing causative allergy. In general, cats tend to develop lesions infiltrated with eosinophils. Lesions are highly pruritic to the point of self-mutilation. The classic lesions that make up this complex are: 1) miliary dermatitis (tiny millimeter sized crusted papules), 2) eosinophilic granulomas (mouth, lateral pelvic limbs or interdigital), 3) rodent/indolent ulcer (eosinophilic ulcer on upper maxillary lip margin) and 4) eosinophilic plaque (ventral abdomen or dorsal head). Identifying these lesions on a cat is helpful in understanding that an allergy is most likely driving the dermatological abnormalities. Additional workup is required to determine which allergy or allergies play a role. Prominent lesions of the eosinophilic granuloma complex. Multiple eosinophilic granulomas on the medial pelvic limb. Image courtesy of Dr. Amelia G. White.
FLEA BITE HYPERSENSITIVITY Pathogenesis
Flea bite hypersensitivity, or flea allergy, is the most common type of allergy in the cat (and in the dog). It occurs when the cat is sensitized to flea salivary proteins. While in dogs it has been demonstrated that intermittent flea exposure is associated with
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