Seasonal flank alopecia in dogs
4-year-old spayed female Boxer that every autumn–winter develops well-demarcated, geographic, hyperpigmented alopecia on both flanks without pruritus. The hair regrows on its own in spring. General examination and blood tests are normal.
What is the most appropriate approach?
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A. Start empirical levothyroxine, as symmetrical alopecia suggests hypothyroidism
Empirical treatment without a diagnosis is a mistake: the seasonal pattern with spontaneous regrowth and normal blood tests are not typical of hypothyroidism.
B. Clinical diagnosis of seasonal flank alopecia: explain it is cosmetic and consider melatonin
Correct. The breed, geographic flank distribution and seasonal recurrence with spontaneous regrowth are diagnostic. No treatment is required; melatonin before the expected season may reduce episodes in some dogs.
C. Take a fungal culture and treat with itraconazole for suspected dermatophytosis
Dermatophytosis does not follow a bilateral symmetrical seasonal pattern with spontaneous regrowth every year, nor does it spare the rest of the body in this way.
D. Perform an ACTH stimulation test and treat with trilostane
There are no signs of hypercortisolism (polyuria, polyphagia, thin skin) and trilostane is not indicated for a cosmetic alopecia.
lightbulb Key takeaway
Predisposed breeds: Boxer, English Bulldog, Airedale, Schnauzer and Korthals Griffon. It is linked to photoperiod: in the northern hemisphere it usually starts between late autumn and spring. Some episodes do not fully regrow or the hair returns a different colour; if the presentation is atypical, rule out endocrine disease before labelling it.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.