Scratches is a chronic, seborrheic dermatitis characterized by hypertrophy and exudation on the caudal surface of the pastern and fetlock. It often is associated with poor stable hygiene, but no specific cause is known. Heavy horses (eg, draft horses) are particularly susceptible, and the hindlimbs are affected more commonly. Standardbreds can be affected in the spring when tracks are wet.
Scratches may go unnoticed if hidden by the “feather” at the back of the pastern. The skin is itchy, sensitive, and swollen during the acute stages; later, it becomes thickened and most of the hair is lost. Only the shorter hairs remain, and these stand erect. The surface of the skin is soft, and the grayish exudate commonly has a fetid odor. The condition can become chronic, with vegetative granulomas. Lameness may or may not be present; it can be severe and associated with generalized cellulitis of the limb. As the condition progresses, there is thickening and hardening of the skin of the affected regions, with rapid hypertrophy of subcutaneous fibrous tissue.
Persistent and aggressive treatment is usually successful. This consists of removing the hair, regular washing and cleansing with warm water and soap to remove all soft exudate, drying, and applying an astringent dressing. If granulomas appear, they can be cauterized. Cellulitis requires systemic antibiotic therapy and tetanus prophylaxis.
Last full review/revision September 2015 by James K. Belknap, DVM, PhD, DACVS