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Feline Atopic Skin Syndrome

William Oldenhoff, DVM, DACVD, ACCESS Specialty Animal Hospital, San Fernando Valley, California


November/December 2021

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In the Literature

Santoro D, Pucheu-Haston CM, Prost C, Mueller RS, Jackson H. Clinical signs and diagnosis of feline atopic syndrome: detailed guidelines for a correct diagnosis. Vet Dermatol. 2021;32(1):26-e6.


The nomenclature surrounding feline allergic dermatitis caused by environmental allergy is complicated. Atopic dermatitis is not generally used, as environmentally allergic cats lack many of the hallmarks of atopic dermatitis seen in dogs and humans. Alternate terminology (eg, nonflea, nonfood-induced hypersensitivity dermatitis) has thus been used, but clearer and more understandable clinical classification is required. Feline atopic syndrome describes all allergic diseases in cats, including flea allergy dermatitis, feline food allergy, feline asthma, and feline atopic skin syndrome; therefore, feline atopic skin syndrome (FASS) is now the preferred term for cats with allergic dermatitis due to environmental allergy. 

This study sought to summarize the current literature on the clinical presentation of FASS and develop diagnostic guidelines. Patients with FASS are typically presented with one or more reaction patterns (ie, miliary dermatitis; self-induced alopecia; face, head, and neck pruritus; eosinophilic granuloma complex). Although mean age of onset varies widely, most reports suggest a young age of onset that ranges from 0.5 to 4.8 years of age.1-7 Female cats1-5,8-10 and Abyssinians6,7 may be overrepresented. There is also evidence of heritability, as is seen in humans and dogs.11-15  

Patients with feline food allergy can be presented with the same reaction patterns as patients with FASS. Other differential diagnoses include ectoparasites, staphylococcal skin infection, and Malassezia spp overgrowth. FASS can be diagnosed when other differential diagnoses, including food allergy, are ruled out. 

Allergen testing should be performed after clinical diagnosis is made and should be used to formulate immunotherapy. Intradermal testing is considered the gold standard but lacks standardization and is generally considered to be more difficult to perform in cats as compared with dogs. Allergen-specific immunoglobulin E serology is widely used but also lacks standardization, and there are reliability concerns.


Key pearls to put into practice:


Correct diagnosis of FASS requires understanding of typical presentation and methodically ruling out other causes of skin disease, including treating skin infections and ruling out ectoparasites and food allergies.


Appropriate use of allergy tests is critical. Intradermal and serum allergy tests do not result in an FASS diagnosis; allergy testing should instead be used as a guide to allergen selection in allergen-specific immunotherapy. Diagnosis is achieved through the clinical process. Allergy testing should only be pursued if the pet owner is committed to immunotherapy, not with the goal of learning which allergens need to be avoided, as allergen avoidance is usually not possible.


Immunotherapy is the only treatment that can reverse allergy progression. Therapies to control clinical signs are important to maintain patient comfort but do not stop disease progression. For most allergic patients, allergen-specific immunotherapy is recommended because it is the safest long-term treatment option.


For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

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