Focal alopecia in the dog

Abstract

Focal alopecia is a common dermatological sign in the dog. Self-inflicted trauma can cause focal alopecia; where there is evidence of this the investigation of hair loss should follow that for pruritic skin disease. Where pruritus is not a significant cause of hair loss, focal alopecia may be inflammatory or non-inflammatory in nature. The former is caused by a direct inflammatory insult to the hair follicle; the latter by abnormalities in hair formation (follicular dysplasia) or interruptions in the normal hair growth cycle (hair cycle arrest). A logical approach to cases should include a carefully taken history, general physical examination and dermatological examination, followed by appropriate diagnostic tests. Skin scrape assessment for dermatophytes and trichography are useful in all cases. Further diagnostic tests such as blood samples and biopsies may be needed in some dogs.