Dandruff in horses (seborrhoea) is a flaky, scaly disease of the skin. It is not an itchy skin disorder, and secondary bacterial infection is not always a problem. Seborrhoea is classified as either primary or secondary. Either form may be dry or oily.
Primary seborrhoea is rare and primarily seen on the mane, tail and front of the cannon--front of the leg, below the knee--of the hind limbs. Primary seborrhoea is sometimes called "stud crud," even though it is not limited to stallions (sexually intact males).
Secondary seborrhoea is associated with skin infection, nutritional deficiencies, liver disease, intestinal malabsorption, vitamin A deficiency, sex hormone imbalances and autoimmune skin diseases.
Dry seborrhoea is characterised by scaling and flaking that looks much like dandruff. According to Dr. Christine Rees, DVM, Texas A & M Univ., the skin itself is relatively healthy, but the condition may be caused by nutritional problems.
Oily seborrhoea scales are held together by sebum, forming thick, yellow-brown crusts. As the crusts peel off, you may see bare patches of skin up to 8 inches in diameter. Over time, the skin becomes thickened and inelastic and the horse generally loses weight and condition.
Primary seborrhoea is incurable but can be managed with topical medications. Secondary seborrhoea may clear up when the underlying cause is treated. For dry seborrhoea, clipping the coat regularly and using a product which contains sulfa or sulphur, a salicylic acid shampoo or a catalytic product aids in keeping the skin free of flakes. Benzoyl peroxide and sebum-dissolving shampoos help to loosen scales in horses with oily seborrhoea. Topical and oral antibiotics are administered when there is a secondary bacterial infection.