Nasal Solar Dermatitis (Collie Nose) in dogs

This is a weepy, crusty dermatitis that affects Collies, Australian Shepherds, Shetland Sheepdogs, and related breeds. It is seen most commonly in sunny regions such as Florida, California, and the mountainous regions of the West. It is caused by lack of pigment on the nose and prolonged exposure to the ultraviolet rays in sunlight. Lack of pigment is hereditary in some dogs, but it can be acquired through skin diseases and scarring.

Initially, the skin appears normal except for the lack of black pigment. With exposure to sunlight, the skin at the border between the muzzle and nose becomes irritated. As the irritation continues, hair falls out and the skin begins to ooze and crust. With continued exposure, the skin breaks down. In advanced cases, the whole surface of the nose becomes ulcerated and the tip itself may disappear, leaving unsightly tissue that bleeds easily. Skin cancer may develop.

Nasal solar dermatitis must be distinguished from discoid lupus erythematosus, pemphigus foliaceus, and zinc responsive dermatosis  (skin diseases in dogs). All three diseases produce a skin reaction similar to nasal solar dermatitis. A distinguishing feature of nasal solar dermatitis is that pig- ment was lacking before the disease developed. In the other three, the pigment disappears as the disease progresses. Note that once depigmentation occurs in dogs with these diseases, the damaging effects of sunlight add to the problem.

Treatment: Prevent further exposure by keeping your dog indoors as much as possible when the sunlight is the most intense—between 9 a.m. and 3 p.m. Letting the dog out on cloudy days does not address the problem, because ultraviolet rays penetrate clouds. Sunscreens are of some aid in protecting dogs who spend time outdoors. Use products containing an SPF greater than 15. Apply the sunscreen 30 to 60 minutes before exposure and again later in the day. Treat an irritated nose with a skin preparation such as Cortaid that contains 0.5 to 1.0 percent hydrocortisone.