Snow nose is most often a temporary loss of pigment in the center of the nose. A pink-to-brown light stripe appears in the center of the nose, with the edges of the nose remaining black. The nose returns to its full black color during months with longer daylight. Snow nose was once thought to be a condition found only in cold climates, hence the name, but dogs in warmer southern climates have also been reported to have snow nose. As dogs age, the snow nose might stay around all year long.
The cause is not completely understood. Snow nose is more common in light and white-coated breeds. This condition by itself isn't a health problem, but caution is advised in sunny weather because the depigmented area is at increased risk for getting sunburned. Some vets advise testing the thyroid levels to make sure that there isn't an underlying thyroid problem in your dog.
Other Things to Consider
Other conditions can cause a loss of pigmentation on a dog's nose. If you use plastic food and water bowls for your dog, for instance, a change in nose color could be a reaction to the plastic. Try switching to glass, ceramic, or stainless steel bowls and see if the snow nose goes away.
Snow nose is not a health concern, but any changes in your dog's nose, including crusts, sores, discharge, sneezing, or wheezing, should be checked as soon as possible by your veterinarian.