Generalised Demodectic mange is a potentially debilitating skin condition of dogs caused by Demodex canis, the demodectic mite. Mites are often transmitted from a nursing bitch to her puppies and in adult dogs appear when the immune system is weak. Certain dog breeds are more sensitive to demodectic mange. Lesions initially appear on the muzzle and paws, which then spread all over the animal.

Localized cases occur when these mites proliferate in one or two small, confined areas. This results in isolated scaly bald patches-usually on the dog's face-creating a polka-dot appearance. Localized demodicosis is considered a common ailment of puppyhood, and approximately 90% of cases resolve with no treatment of any kind.

Generalized demodectic mange, in contrast, affects larger areas of skin or a dog’s entire body. Secondary bacterial infections make this a very itchy and often smelly skin disease. This form of mange could also be a sign of a compromised immune system, hereditary problem, endocrine problem or other underlying health issue. Treatment depends on the age at which the dog developed the disease.