A 2-year-old spayed female cat has severe facial pruritus with linear ulcers. What is the most appropriate next diagnostic step?

In the case of a 2-year-old spayed female cat presenting with severe facial pruritus accompanied by linear ulcers, a hypoallergenic diet trial represents a logical next step. This approach aims to rule out food allergies as a contributing factor to the cat's skin issues.

Food allergies in cats can manifest in various ways, including pruritus and skin lesions. By initiating a trial of a hypoallergenic diet, which is formulated with novel protein sources or hydrolyzed proteins that the cat has not previously consumed, it allows for the observation of clinical improvement. If the cat's symptoms subside during the diet trial and reappear upon reintroduction of the original diet, it provides evidence supporting a food allergy diagnosis.

This method is often preferred initially as it is non-invasive and avoids the side effects associated with pharmacological treatments. Other options, such as allergy testing, can be less reliable due to varying sensitivity and specificity in diagnosing food allergies, and may not address immediate clinical concerns. Similarly, corticosteroids like methylprednisolone and immunosuppressants like cyclosporine can alleviate symptoms, but they do not provide insight into the underlying cause of the pruritus and may mask the problem instead of addressing it directly. Therefore, a trial