Allergy may be the primary cause of or a contributing factor for anal sac disease. It is thus important during physical examination to look for subtle changes (eg, erythema or alopecia on the paws, erythema on the pinnae or inside the ear canals) owners may not observe in the home. Patients may be presented for signs of anal sac disease only, as owners typically focus on the odor and perceived mess associated with anal sac problems and overlook classic signs of allergy (eg, scratching, licking paws). In one study of patients with recurrent anal sac disease, atopic dermatitis was the most common comorbidity.4
Patients with signs of allergic dermatitis should undergo an allergy workup, typically starting with an 8- to 10-week elimination diet trial. Treatment for environmental allergy can be initiated if response is not beneficial. Allergen-specific immunotherapy based on allergy testing is a safe and effective long-term treatment option. Other allergy treatment options include oral corticosteroids, oral cyclosporine, and oral oclacitinib. Reducing allergy triggered inflammation is the primary mechanism of allergy therapy for prevention of anal sac disease. Consequently, oclacitinib is usually least beneficial for long-term control due to its primary mechanism of action, which is to block interleukin-31 and the sensation of itch. In addition, quality flea prevention is essential for all allergy patients, as flea bites can trigger a food or environmental allergy flare, even without presence of a flea allergy. Response to treatment should be based on behavior in the home and rectal examination with anal sac expression/palpation.