Greasy or flaky skin in dogs is often a symptom of a skin condition called Seborrhea. It can be severe and obvious but more commonly is mild and can go unnoticed. Normal skin is constantly being replaced in a 4-week cycle, Seborrhea happens due to an imbalance between new and dying skin cells.
There are two forms of seborrhea: oily (oleosa) and dry (sicca). A combination of both is frequent. A change in the amount and quality of the oily skin secretions (sebum) caused seborrhea. It can be generalised and affect the majority of the dog's skin or localised affecting just small areas.
Underlying disease such as allergies, endocrine disorders or dietary deficiencies can be causes of Seborrhea. In moderate to severe cases, it is important to have your dog checked for these underlying causes as they may need specific treatment.
Primary (inherited) seborrhea also exists. It affects young dogs of certain breeds including Westies, Dachshunds, and Labrador Retrievers commonly. In Shar Peis, primary seborrhea is common in the body folds.
Sebborheic skin exudes a waxy, greasy substance and occasionally you may see comedones (blackheads). Often, dogs have an unpleasant smell due to this excessive production of fatty acids which gives a characteristic odour of "wet dog".
With dry seborrhea, dandruff is more frequent and a lack of sebum irritates the skin. Skin darkening (hyperpigmentation) and hair loss are also common.
The damage to the natural protective skin barrier creates a favourable place for bacterial or yeast infections and itching may appear too. The ears or the tail ('stud tail') are sometimes affected or it may be that only one part of the body is involved.
Stud tail is an overactive sebaceous gland with seborrhea symptoms limited to the upper part of the tail.