Diagnosis and Treatment of Pruritus in Cats Algorithm

Feline patients with pruritus typically present with 1 or more of 4 cutaneous reaction patterns: head and neck pruritus, self-induced alopecia, eosinophilic granuloma complex, and miliary dermatitis.¹ These patterns can be seen with any pruritic condition and are not restricted to cats with feline atopic syndrome.¹ Owners of pruritic cats may be unaware that the patient is pruritic and may present them for these cutaneous lesions.¹ Overgrooming may be interpreted as normal grooming behavior by some owners.¹ In cats with self-induced alopecia, pruritus is more likely than behavioral overgrooming, and psychogenic alopecia is likely overdiagnosed.¹ It is important for the clinician to consider differentials for pruritus when presented with a cat demonstrating any of the cutaneous reaction patterns, regardless of whether the owner brings up pruritus as a concern.

Parasites

Flea allergy is common in cats and should be considered in any cat not receiving regular preventives, even if kept indoors or if living in a household with unaffected cats. Cats with fleas or flea allergy may groom fastidiously, making it difficult to find evidence of fleas on examination. Demodex gatoi can cause severe pruritus in cats and may not be seen in skin scrapings in infested cats, nor do all exposed cats develop pruritus.² Empiric treatment for demodicosis should be considered for any itchy cat.

Infections

Fungal and bacterial infections should be excluded as a primary or contributing factor to the pruritus.¹ In cats, dermatophytosis may cause pruritus and should be ruled out,¹ especially if alopecia is part of the clinical presentation. In the author’s experience, bacterial infection is seen less often in atopic cats than in dogs; therefore, treating empirically with antibiotics without cytologic evidence of infection is not recommended. Rods may be seen as oral flora from overgrooming and are not always indicative of infection. Yeast overgrowth in cats is often associated with atopy¹ but has been associated with underlying systemic disease; therefore, additional workup should be considered when identified.³ Sphynx and Devon Rex breeds may also be predisposed to yeast overgrowth.³

Allergies

If the patient remains pruritic after ectoparasites and any infection have been controlled, then allergies should be considered.¹ If there is a clear pattern of seasonal worsening, a diagnosis of feline atopic skin syndrome (FASS) or environmental allergies can be made.¹ In a cat with year-round symptoms that worsen seasonally, concurrent food and environmental allergies are a possibility. In any cat affected clinically year-round, an elimination diet trial is recommended to evaluate for possible food allergy.¹ Glucocorticoids can be used during the diet trial to manage clinical signs but must be tapered to evaluate response to the diet.

Once a diagnosis of FASS has been confirmed, allergen-specific immunotherapy (ASIT) should be discussed. ASIT is most commonly administered subcutaneously or sublingually with the route based on the individual cat’s tolerance and owner preference. Because ASIT can take several months before clinical benefit is seen, symptomatic control should be considered regardless of whether ASIT is elected (TABLE 1).