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SEASONAL FLANK ALOPECIA
ALSO CALLED "CANINE FLANK ALOPECIA," "CYCLIC FLANK ALOPECIA,"
WHAT IS THIS?
(original graphic by marvistavet.com)
Seasonal flank alopecia is exactly what it sounds like, though it helps to know that the word "alopecia" means hair loss. With seasonal flank alopecia, a dog loses hair in the flank area on a seasonal basis. Different dogs seem to choose different seasons to lose their hair (fall and spring are popular) and when the season changes the hair generally grows back. Sometimes a dog will skip a season only to lose hair again the next year. Most affected dogs are Boxers, Airedales, and English bulldogs though numerous other breeds have been affected.
The hair loss is generally confined to the flanks (area just ahead of the rear legs) though sometimes the bridge of the nose is involved. The skin typically is darkly pigmented in the areas of hair loss. Both flanks are generally affected symmetrically and sometimes there is skin infection present in the balding areas. Sometimes the hair re-grows in a different color than the original hair. Some dogs never re-grow their hair.
Diagnosis is generally made by the classic appearance of the pigmented bald spot and the the history of recurrence. Diagnosis can be confirmed with skin biopsy if more confirmation is desired.
WHY DOES THIS HAPPEN?
At the present time no one knows why this occurs. It is felt to relate to the effects that daylight cycle and light exposure have on the pineal gland. Shorter days seem to lead to a decrease in melatonin from the pineal gland and this leads to the skin change. Breed predisposition suggests a genetic factor as well. Dogs of any age can be affected but the average age is about 4 years.
IMPLANT UNDER THE SKIN
A possibly more effective method seems to involve the use of melatonin implants under the skin. These were not available in the U.S. until recently. A small implant the size of a grain of rice is implanted between the shoulders much in the same way as a microchip ID is implanted. If hair regrows and it seems to work, the a new implant can be inserted every 4-6 months. Some drowsiness can be a side effect for the first 1-3 days and occasionally a sterile abscess forms at the site necessitating removal of the implant.
Seasonal flank alopecia is a cosmetic problem which is not harmful to the dog. It is not unreasonable to leave it untreated. Discuss these options with your veterinarian.
Page last updated: 5/27/2023