Seasonal alopecia, also called seasonal flank alopecia and light responsive alopecia, is a recurrent hair-loss condition that affects dogs, cats, horses, cows and pigs, according to the Merck Veterinary Manual. Alopecia is the partial or total hair loss in areas of the body where hair usually grows. Animals with seasonal alopecia lose hair on their flanks during certain times of the year. Veterinarians usually begin the process of identifying and treating seasonal alopecia by ruling out causes for the animal's hair loss.
The several types of alopecia have many causes; however, veterinarians have determined that seasonal alopecia is nonpruritic, which means the hair loss is not caused by unexplained itching and scratching, and noninflammatory. While hair loss occurs mostly in the flank area, hair loss can occur on the bridge of the nose. Although your dog can have seasonal hair loss happens in any season, most animals lose their hair in the spring or fall.
Animals with seasonal hair loss usually grow new hair after the season ends. Often, an animal may skip a season of hair loss and lose their hair in the following season. Your animal's flanks show symmetrical hair loss and its skin is darker in the hair loss areas. A skin infection might affect the balding areas and the skin might appear scaly and thin. Your animal's new hair might be a different color than the original hair. Some animals never grow new hair in the balding spots.
Many dog breeds are affected by seasonal alopecia, but those that appear to be affected most are Airedales, boxers and English bulldogs. Other dogs with a high incidence are griffons, schnauzers and bearded collies. Seasonal alopecia is more common among animals in higher latitudes, according to the District of Columbia Academy of Veterinary Medicine. Some veterinarians believe that seasonal alopecia, or light responsive alopecia, affects animals during seasons when days are shorter and animals get less sunlight, especially house-bound pets and animals in areas with dark winters.
Your veterinarian might perform an examination, tests and skin biopsies to make a diagnosis of seasonal alopecia. Some veterinarians believe the cause is a hormonal condition that affects the hair follicles. Others point to a genetic melatonin deficiency that affects the skin. DVM360, an online veterinary magazine, cites lack of exposure to sunlight as the cause and notes the presence of hyperpigmentation and truncal alopecia in dogs with the condition.
Some veterinarians recommend melatonin as a treatment for seasonal alopecia. Melatonin is a naturally-occurring biochemical used by the body to regulate circadian rhythms. Melatonin can shorten the hair loss episode and prevent recurrence, according to the District of Columbia Academy of Veterinary Medicine, which reports a 50 to 75 percent positive response rate to melatonin treatment. Melatonin, in oral form or injections, is given until your animal begins to grow healthy hair. Melatonin also is used to prevent or treat future occurrences of the condition. Some veterinarians prescribe oral melatonin and increased sunlight exposure to treat seasonal alopecia. Animals receiving treatment have varying degrees of success at growing new hair.