Bob Judd, DVM, DABVP (Equine Medicine), DABVP (Canine and Feline Practice)
Some horses can develop a lack of skin pigmentation, usually around their eyes, called vitiligo. If you have seen horses with a lack of pigment in some regions of the skin and there is no inflammation, vitiligo is possible.
Fortunately, the condition is cosmetic only and has no detrimental effects on the horse. Equine nutritionist Dr. Clair Thunes, Ph.D., states in the publication The Horse that the syndrome is thought to be an immune-mediated condition and occurs in other mammals, including humans, dogs, and pigs.
An animal’s immune system attacks and kills melanocytes, which are the cells that produce the pigment in the animal’s skin. When these cells are destroyed, the skin becomes white or unpigmented.
The disease was mentioned 3500 years ago in humans, but the first known report in horses was in 1931. That does not mean the condition did not exist before, but there were no scientific reports.
The disease can occur in several breeds and is particularly common in Arabians. It is referred to as Arabian fading syndrome or pinky syndrome. Arabian mares sometimes develop the condition around their eyes when pregnant, but it is unknown why this happens.
It is thought that vitiligo can be stress-related, as it comes and goes, and could be why it occurs in pregnant mares. Doctors have tried numerous treatments on people with varying results.
Nutritional changes may help in some horses. In a study, one horse with this condition was supplemented with vitamins A, D, E, and B12, while another horse was fed excessive copper supplements. Both horses had their conditions resolved, but treatments are difficult to evaluate scientifically in a disease where the symptoms come and go, so it is hard to prove that vitamins and copper played a role in the resolution of vitiligo in these two horses.
If you think your horse may have vitiligo, consult with your veterinarian to rule out any other skin condition.