Radiation‐Induced Alopecia in Dogs With Nasal Tumours: Coat Type Influences Development and Onset

BACKGROUND: Radiation-induced alopecia (RIA) is a common adverse effect of radiation therapy, yet factors influencing its development in dogs remain unclear. OBJECTIVES: To characterise acute RIA in dogs with nasal tumours and to evaluate associations with coat type and radiation dose. ANIMALS: Thirty-eight client-owned dogs were treated with radiation therapy for nasal tumours. MATERIALS AND METHODS: Medical records were reviewed retrospectively. Dogs were classified by coat type (straight versus curly or wire-haired). Time to onset of alopecia was assessed as the interval from the first irradiation to the first detection of alopecia, and cumulative skin dose was calculated up to alopecia onset. Dogs developing acute RIA during radiation therapy were compared with those without RIA. Dogs developing alopecia only after completion of radiation therapy were excluded. RESULTS: Seventeen of 34 dogs developed acute RIA during radiation therapy. Coat type was significantly associated with RIA development (p = 0.003), with all dogs with curly or wire-haired coats affected. These dogs developed RIA earlier than those with straight-haired coats (median 14 versus 20 days; p = 0.047). Within affected dogs, RIA developed first in regions receiving higher skin doses and subsequently progressed to regions receiving lower skin doses. CONCLUSIONS AND CLINICAL RELEVANCE: Coat type influences the development of acute RIA in dogs, with curly or wire-haired breeds showing earlier onset and greater extent of alopecia. Alopecia progression reflects regional skin dose distribution. These findings may assist clinicians in predicting the risk of RIA and informing owners about the potential development and timing of radiation-induced alopecia.