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) causes this condition. An imbalance between new and dying skin cells causes the flakes on your dog's coat and excessive skin peeling.
Underlying conditions such as allergies, endocrine disorders, and dietary deficiencies are common. These conditions cause an imbalance of the skin's ecosystem leading to secondary seborrhea.
Primary (inherited) seborrhea also exists. It affects young dogs of certain breeds including West Highland White Terriers, Dachshunds, Labrador Retrievers and others. In Shar Peis, primary seborrhoea is common in the body folds.
Oily skin can be waxy or greasy. Often, dogs have a bad odor due to this excessive sebum production.
With dry seborrhea, dandruff is more frequent and a lack of sebum irritates the skin. Skin hyperpigmentation and hair loss are also common.