If your horse is beginning to look rather scruffy and is losing hair instead of beginning to put on a fine winter coat, the reason may be a case of seasonal alopecia also called seasonal flank alopecia since it often affects the flanks of horses.
Seasonal alopecia affects many mammals including horses 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 and other body parts 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.
With seasonal alopecia, the hair loss is not caused by scratching or itching and the skin does not become inflamed. Although it can occur at any time of the year, it usually occurs in the spring and the fall.
The normal pattern of hair growth in horses is triggered by the shortening and lengthening of day light periods as the seasons change. The pineal gland responds to the changes in daylight, producing more or less melatonin and thus influencing hair growth.
Some horses vary from the normal pattern, growing hair at regular times but soon losing it over some areas of the body. Known as seasonal alopecia, this condition may be caused by an imbalance in the pineal gland which fails to regulate the production of melatonin in relationship to the changes in daylight.
Horses hair coats are also influenced by disease, stress, and fever. Pituitary pars intermedia dysfunction known as Cushing’s disease is a cause of hair coat abnormalities in older horses.
The timing and type of light used in stables, barns and paddocks can be an influence on unusual shedding because the light wavelength from these sources is similar to that of natural sunlight. Keeping a horse on a more natural lighting schedule may help to prevent hair loss.
Horses that lose too much hair in the winter may need to be blanketed for warmth, and those that develop a very thin coat in the summer should be observed for sunburn. Other than these considerations, seasonal alopecia is not known to have negative effects on a horse’s health.
A veterinarian should be consulted about any horse that has unusual hair loss. If the hair loss results from dermatitis in some form, it is not seasonal alopecia and diagnostic tests such as skin biopsy, skin scraping, and fungal culture can help to find a definitive diagnosis so that appropriate treatment may be given.