All horses occasionally spend their time scratching. Besides feeling good it removes loose hair, parasites, and mud. But when the scratching becomes obsessive to the point of breaking hairs and self mutilation there usually is a disease process going on. Some of the more common places horse's itch are mane and tail and the ventral midline.

This article helps differentiate these diseases on the basis of their appearance and history. Some of the more important diseases then have articles on them, and a link is provided to a more thorough discussion.

The most common causes of primary itching in horses are insect bites. Some diseases which are not normally itchy may cause a hypersensitivity reaction, scratching, and hair loss. Usually in these cases a primary skin disease is noticed prior to the scratching. Less common problems are autoimmune skin diseases and rare are the food allergy and contact sensitivities. Some of the infectious skin diseases can cause secondary itching also. A list of causes of itchiness (medical term is pruritus) in horses includes:

• biting midges: culicoides, horn flies, buffalo gnats
• ticks
• any chemical applied to the skin
• lice and mange mites
• bacterial and fungal skin diseases: ringworm, dermatophilus, grease heel
• onchocerca
• pinworms
• certain plants and shavings: yellow poplar shavings
• autoimmune diseases: pemphigus

Though the list looks formidable, an exam and careful history will greatly reduce the number of possibilities.