Melanin is a natural sunscreen. Humans can increase the production of melanin by repeated exposure to the sun. Dogs don't have melanin in their skin the way humans do, they are in particular danger from sunburns by being shaved or excessive hair loss.

Skin is the largest organ of any living being. In dogs, skin acts as a protective shield from ultraviolet rays, hot and cold weather, and guards against dehydration by preventing fluid loss. Skin is exposed to both internal and external attacks by parasites, mites, scratching, licking, pollution, and other foreign particles.
Skin diseases are a common problem in all dogs. Skin disorders can be infectious, long lasting, contagious, and in some cases indicative of other pre-disposed diseases.
Read through the list of common skin diseases to understand the common causes and symptoms of each disease.