Dog skin disorders are among the most common health problems in dogs. Skin disorders in dogs have many causes, and many of the common skin disorders that afflict people have a counterpart in dogs. The condition of dog's skin and coat can also be an important indicator of its general health. Skin disorders of dogs vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. They also need to be differentiated on the basis of being of primary or secondary (due to scratching, itch) in nature, making diagnosis complicated. Dog skin disorders may be grouped into categories according to the causes.

Skin disease may result from deficiency or overactivity of immune responses. In cases where there is insufficient immune responses the disease is usually described by the secondary disease that results. Examples include increased susceptibility to demodectic mange and recurrent skin infections, such as Malassezia infection or bacterial infections. Increased, but harmful immune responses, can be divided into hypersensitivity disorders such as atopic dermatitis, and autoimmune disorders (autoimmunity), such as pemphigus and discoid lupus erythematosus.

The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals, except that it is not protected by a pelt. Though nearly all human skin is covered with hair follicles, it appears hairless. There are two general types of skin, hairy and glabrous skin. The adjective cutaneous literally means "of the skin" (from Latin cutis, skin).

Because it interfaces with the environment, skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue. This is often discolored and depigmented.

In humans, skin pigmentation varies among populations, and skin type can range from dry to oily. Such skin variety provides a rich and diverse habitat for bacteria which number roughly at 1000 species from 19 phyla.