Seasonal alopecia or cyclic follicular dysplasia is the condition where a dog starts losing hair on the flanks and on the back. The skin becomes darker at the places where the hair loss is present and the hair becomes somewhat coarse and dry. The condition usually starts in the late fall or the early spring. It lasts for up to 6 months and the hair usually regrows after that. Seasonal alopecia can keep occurring in the future (possibly every year), or it can occur only once and never show up again. Dogs that are affected by this condition are usually 2 to 4 years of age. There is no proven reason for why this condition occurs, but some believe that lack of sunlight might play a role. The reasoning behind this is that during the long and cold winters, dogs spend less time outdoors and there is less sunlight. Many dogs start exhibiting the condition in the early spring as a result of this. Some suggest treatment with melatonin to speed up the regrowth of hair. However, no proof exists that melatonin is in fact responsible for the hair regrowth. Breeds that are more susceptible to this condition than others are: Affenpinscher, Airedale Terrier, Boxer, Bulldog, Staffordshire Terrier, and Wirehaired Pointing Griffon.

Note: Before concluding that your dog has seasonal alopecia, make sure that the veterinarian rules out thyroid disease which has similar symptoms. To check for this, a blood test needs to be performed. Also, the veterinarian may want to take a small skin sample to test for parasites and mites and certain bacteria.