Skin color is determined by melanocyte cells in the skin. Those cells produce melanin which gives skin its color. When skin is exposed to the sun, those cells are stimulated to produce more melanin. That’s how you get a suntan. But what can cause the opposite result? Obviously dogs, like people, come in many different shades. (Dogs can even be albinos – or lacking in pigment altogether.) That means that some dogs are less pigmented to start with. But why might your dog lose that original coloration and develop depigmentation? Let’s discuss some of the possible reasons.
Skin color changing as a result of age
I’m sure you’ve known dogs that go gray as they get older – especially on their faces. According to the Veterinary Internal Medicine textbook, such age-associated graying is a result of decreasing numbers of melanocytes and occurs most frequently in German Shepherds, Labradors, Golden Retrievers and Irish Setters.
Skin color changing as a result season
There are other breeds of dogs that are prone to a seasonal lightening of the nasal planum (the hard, tough, hairless end of their nose). Sometimes referred to as “Snow Nose” these dogs (Siberian Huskies, Labradors and Golden Retrievers) can have darker noses in the summer months and lighter noses in the winter. These same breeds plus German Shepherds, Samoyeds, Afghan Hounds and Dobermans (among others) can also experience a gradual or waxing and lightening or fading of their nose color over time. This condition is known as “Dudley Nose1."
You may know people with vitiligo which, according to Davidson College research, is a progressive disease in which the melanocytes are gradually destroyed causing unpigmented areas on the skin. Dogs can also develop vitiligo. They, too, develop pigment loss from their skin or hair on their heads, but it can occur in other locations too. In some cases, antibodies against melanocytes have been identified in the serum of infected dogs indicating an immune component to the disorder. And skin biopsies of the affected areas will typically reveal a total lack of any remaining melanocytes.
What all three of these causes for depigmentation have is common is the fact that they are not a disease that can bother or hurt your dog at all. There is no reason to worry about them and there is nothing to be done to ‘correct’ them. The depigmentation is purely cosmetic.
Skin color changing as a result of outside influences
For instance, any contact dermatitis/irritation can cause depigmentation as can certain chemicals in rubber that can affect the production of melanin pigment where the rubber touches the skin1. According to the Veterinary Internal Medicine textbook, the administration of certain drugs like ketoconazole, procainamide, and vitamin E have been reported to cause generalized changes in coat color in dogs, and injections of other drugs (glucocorticoids, for instance) can cause localized loss of pigment.
Skin color could be more serious
Hormonal disorders (imbalances of thyroid, adrenal or sex hormones) can alter pigmentation as can bacterial and fungal infections and even cancers (neoplasias). Immune-mediated diseases also occur in dogs where the dog’s own antibodies attack different parts of the skin resulting in depigmentation.
Discoid lupus erythematosus is one such disorder and the second most common immune-mediated disease in dogs. Discoid lupus causes not only depigmentation of the nasal planum but also progresses to the formation of swelling, erosions, ulcers and crusting which are aggravated by UV light exposure; and chronic cases have been reported to develop into squamous cell carcinoma cancers2. Other serious immune-mediated diseases affecting the skin and causing depigmentation include pemphigus erythematosus, systemic lupus erythematosus, pemphigus foliaceus and uveodermatologic syndrome (Vogt-Koyanagi-Harada-Like Syndrome).
The take home message is that changes in your dog’s hair or skin color are often benign changes without any serious consequences to your dog’s overall health. However, sometimes that is not the case and a serious problem needs to be seriously addressed. It is up to you and your veterinarian to evaluate your dog and to perform whatever diagnostic tests are necessary in order to distinguish between the two so that you can respond appropriately.
If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.
1. Ettinger, Stephen J., and Edward C. Feldman. "Veterinary Internal Medicine." Inkling. Elsevier, 2010. Web.
2. MacDonald, John, MEd. "Immune Mediated Dermatoses." Western Veterinary Conference 2013. Western Veterinary Conference 2013. Web.