Horse Rain Rot: Bacterial Skin Infection and Welfare

Rain rot (rain scald or dermatophilosis) is a common bacterial skin infection in horses caused by Dermatophilus congolensis. Understanding its causes and treatment protects horse welfare.

Key Facts

Rain rot is caused by Dermatophilus congolensis, a unique organism with characteristics of both bacteria and fungi.
It occurs when prolonged moisture softens the skin, allowing the organism to penetrate, especially in horses without adequate shelter.
Characteristic lesions are matted tufts of hair with crusts underneath, often described as "paintbrush" lesions.
The back, rump, and neck are most commonly affected, but the condition can be widespread in severe cases.
Rain rot is mildly contagious between horses via shared grooming equipment, rugs, and direct contact.
Immunocompromised horses, those under nutritional stress, or those with heavy insect burdens are more susceptible.
Treatment involves removing crusts (painful without softening first), topical antiseptic washes, and sometimes systemic antibiotics for severe cases.

Welfare Considerations

Rain rot causes skin pain, itching, and discomfort in affected horses. The crusted lesions are tender to touch, and horses may show reluctance to be groomed, saddled, or rugged in affected areas. Severe, widespread infections can cause systemic illness. The welfare failure is often one of management — horses kept without adequate shelter in wet conditions, or whose skin condition is not monitored regularly, develop preventable disease. Treatment requires softening and removing crusts, which is uncomfortable for the horse without prior preparation (such as warm water soaking). Good welfare practice requires providing adequate shelter, regularly inspecting the skin under rugs and at friction points, and treating promptly at first signs of lesion development.

What You Can Do

Provide horses with adequate shelter from prolonged rain — field shelters or stabling during wet periods significantly reduce risk.
Inspect your horse's skin regularly under rugs and tack, particularly the back, rump, and girth area.
Do not share grooming equipment, rugs, or tack between affected and unaffected horses.
Treat rain rot by softening crusts with warm water or antiseptic wash before gentle removal to minimise pain.
Consult your vet for systemic antibiotic treatment in severe or widespread cases.
Maintain good nutritional status and parasite control to support skin immunity.