Dog hair loss causes

Q: My boxer, Betsy, started losing her hair last spring, and now it’s happening again. A friend told me that this happens with some dogs, and it’s related to the weather. Can you tell me more? P.L., Farragut

A: Your friend may be thinking about a condition called seasonal flank alopecia. Alopecia is the medical word for “loss of hair.” The hair loss is generally bilateral and on the flanks (the sides of the abdomen).

The condition is not related to the weather, but to the change in seasons. Veterinary researchers believe that the hair loss is related to the number of daylight hours, which rapidly change during the spring and fall. In affected dogs, this causes the hair follicles to stop developing normally. Springtime alopecia tends to be more common than fall.

Although the hair falls out, the exposed skin is relatively normal, although it may become darker and pigmented. Pets are generally not itchy, the skin is not red, and skin infections are uncommon.

We generally see seasonal flank alopecia in young adult dogs, beginning around 2-4 years old. The condition is common in boxers, but certainly can occur in any dog. Most dogs will experience hair regrowth in 4-8 months. A few dogs will have hair grow back a different color, and a few dogs may never have hair regrowth. Dogs with seasonal flank alopecia tend to have annual recurrences.

Melatonin plays a role in regulating circadian rhythms, and supplementing affected dogs with oral melatonin can help some patients.

There are other medical conditions in which dogs lose hair on their lateral flanks, such as disease of the thyroid gland or the adrenal gland. Affected dogs should be examined and have blood testing performed to rule out more serious conditions. If Betsy hasn’t been examined by your veterinarian recently and she is experiencing hair loss again, now is the perfect time to have her examined.

If you have questions about your pet, you may e-mail Dr. Myers at