Demodicosis, also called demodectic mange or red mange, is caused by a sensitivity to and overpopulation of Demodex canis as the animal's immune system is unable to keep the mites under control.
Demodex is a genus of mite in the family Demodicidae. Demodex canis occurs naturally in the hair follicles of most dogs in low numbers around the face and other areas of the body. In most dogs, these mites never cause problems. However, in certain situations, such as an underdeveloped or impaired immune system, intense stress, or malnutrition, the mites can reproduce rapidly, causing symptoms in sensitive dogs that range from mild irritation and hair loss on a small patch of skin to severe and widespread inflammation, secondary infection, and in rare cases can be a life-threatening condition. Small patches of demodicosis often correct themselves over time as the dog's immune system matures, although treatment is usually recommended.
Minor cases of demodectic mange usually do not cause much itching but might cause pustules on the dog's skin, redness, scaling, leathery, hair loss, warm to the touch, or any combination of these. It most commonly appears first on the face, around the eyes, or at the corners of the mouth, and on the forelimbs and paws. May be misdiagnosed as a "hot spot" or other skin ailment.