Seasonal Flank Alopecia

Written by: Dr. Sarah Sims, DVM


Why is my dog’s hair falling out when it is getting colder outside?

It may seem counterintuitive, but hair loss starting in the fall and continuing through early spring is the hallmark of a condition called Seasonal Flank Alopecia. In this condition, there is a disruption in the growth cycle of the hair as the days get shorter. The typical pattern is symmetrical hair loss of the flanks with darkening of the skin:


It mainly affects young adult dogs from the following list of breeds:

  • Airedale
  • Boxer
  • Bulldog (English, American and French)
  • Doberman Pinscher
  • Pitbull
  • Schnauzer

How is Seasonal Alopecia Diagnosed?

There is no tried and true test to confirm the diagnosis of Seasonal Flank Alopecia. The diagnosis is typically made by ruling out the other common causes of hair loss in dogs, such as:

  • Severe allergies
  • Fleas
  • Ringworm
  • Bacterial infections
  • Mange
  • Hypothyroidism
  • Cushing’s disease

If your dog tests negative for all of these other causes, and the alopecia is happening in the darker months and is not itchy, your veterinarian will likely call it Seasonal Flank Alopecia.


Seasonal Flank Alopecia Treatment for Dogs

This is one of the only causes of hair loss in dogs that does not require treatment, as it is only a cosmetic concern. However, if your dog’s baldness is cramping your style, you can try using melatonin supplement from September thru May to encourage the hair’s normal growth cycle to continue.

Dose of Melatonin for Dogs Hair Loss: 2 mg per 10 pounds 3 times per day

For more info on dogs and melatonin check out our post.

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