Seasonal Flank Alopecia

Canine Recurrent Flank Alopecia 

Also Known As: Seasonal Flank Alopecia

Transmission or Cause: An incompletely understood disorder which causes seasonal hair loss on the flanks. This disorder may involve photoperiod changes in melatonin and prolactin hormone production which then affects hair follicles. 

Affected Animals: Most commonly seen in young adult bulldogs, boxers, schnauzers, and airedales. 

Clinical Signs: Non-inflammatory, not itchy hair loss in the flank area. Exposed skin may appear darkened. Hair loss usually affects both sides, but can affect only one side. Hair loss often occurs between November and March and spontaneously regrows several months later. In some dogs the amount of hair loss and the duration before regrowth may increase with each repeated episode and may become permanent. No other signs of disease are seen. 

Diagnosis: Clinical signs and breed are suggestive, but other causes of patchy hair loss include Demodectic mange, ringworm, or hormonal diseases such as hypothyroidism or Cushing’s disease. These diseases should be ruled out by appropriate testing. 

Skin biopsy of affected areas show abnormally shaped hair follicles which are filled with keratin. Treatment: Melatonin can be helpful to prompt hair growth in some dogs and is given daily for two to three months until complete hair growth occurs. Restarting melatonin yearly, four to six weeks prior to anticipated onset of hair loss, may prevent recurrence. 

Prognosis: The prognosis for hair growth is unpredictable. Hair regrowth can be partial and the new hair may grow in a different color and/or texture. This is purely a cosmetic disorder which does not affect the dog’s quality of life.