Malassezia dermatitis, also called yeast or fungal dermatitis, is caused by a type of yeast (fungus) found on the skin and in ears of dogs.
Though a normal inhabitant of these areas, an abnormal overgrowth of this micro-organism can cause a skin inflammation or dermatitis.
It is often triggered by an underlying disease, such as parasites, an endocrine disease or allergies against fleas or food ingredients. Dogs with allergies or oily/flaky skin seems particularly prone to yeast overgrowth.
An overgrowth of yeast causes skin irritation, hair loss, a reddened, greasy, smelly skin with affected patches becoming darker (hyperpigmentation).
In chronic cases, the skin will also become thicker. The arm pits, lower neck, ears, feet and nail beds are most commonly affected. The hair may become red with chronic infection. This is fairly common between the toes or on the chops.
Some breeds of dogs are particularly susceptible to Malassezia dermatitis, including Poodles, Basset hounds and West Highland White Terriers.