Scratches refers to skin crusting and scabbing that affects the lower limbs, below the fetlock. It remains a poorly understood syndrome that can result from allergic, bacterial, fungal, immune-mediated, parasitic, photo-activated, or viral causes, alone or in combination.

It more commonly occurs on the hind limbs, but can affect the front limbs too. In most cases, it affects more than one limb. It is also more common on lower limbs with unpigmented skin with white hair. In a particular horse, it will often only appear on limbs with pink skin. In draft breeds, Chorioptes mites are often part of the problem and require treatment.

Scratches is more common in wet climates and is made worse by wet/dry weather cycles. It is especially common in horses consistently grazing wet pastures and in wet grass.

In some cases, breaks in the skin caused by this condition allows bacteria to enter, causing a very severe infection of the lower limb that appears as sudden onset lameness and limb swelling (Sporadic Lymphangitis). In most cases, a specific diagnosis of the cause for the lesions is not made. Often bacterial infection is a complicating layer on top of the primary cause.

Treatment involves identifying and addressing underlying causes, if possible, and the lesions are often treated with antiseptic shampoos and antibiotic/antifungal/steroid creams.