Rain rot, also known as dermatophilosis, is a bacterial skin infection caused by *Dermatophilus congolensis*. Despite its common name, it is not a fungal infection. The organism thrives in warm, moist conditions and causes characteristic crusty, paintbrush-like scabs along the horse's back, neck, and rump. ## What it is *Dermatophilus congolensis* is an actinomycete bacterium that exists on the skin of many horses without causing disease. When the skin barrier is compromised by prolonged moisture, insect bites, or trauma, the organism invades the epidermis and causes superficial pustules that rupture and form thick crusts. The crusts contain embedded hairs and have a classic "paintbrush" appearance when lifted. ## Signs and symptoms - Tufted, paintbrush-like scabs along the dorsal surface (back, croup, neck, withers) - Hair epilates easily in clumps with pus or crust on the underside - Exposed skin underneath is pink, moist, and sometimes raw - Lesions may spread to the face and legs in severe cases - Usually not pruritic (not itchy), which helps distinguish it from other skin conditions - Worsens significantly during wet weather ## Causes and risk factors Rain rot develops when the skin remains wet for prolonged periods, especially in combination with skin trauma from insects or grooming. Risk factors include poor stable hygiene, horses kept outdoors in wet conditions without shelter, heavy feathering, and compromised immune function. The disease is more common in young horses and during periods of high rainfall. ## How it is diagnosed Diagnosis is usually straightforward based on the characteristic appearance and distribution of lesions. Microscopic examination of crusts can confirm the presence of *Dermatophilus* organisms (railroad track appearance of bacterial filaments). Bacterial culture is occasionally used in complicated cases. ## Treatment and management Treatment involves removing the crusts (after softening with oil or antimicrobial shampoo) and applying topical antibacterial agents. Keeping the horse dry is essential. In severe or widespread cases, systemic antibiotics may be required. Improving stable hygiene and providing shelter from prolonged rain help prevent recurrence. Most cases resolve within 1 to 3 weeks with appropriate treatment. ## When to call the vet Contact your veterinarian if the lesions are widespread, the horse is systemically ill, or the condition does not improve with basic topical treatment within a week or two. Severe cases can lead to secondary infections or significant discomfort. ## Prevention Prevention centers on keeping the horse as dry as possible and maintaining good skin hygiene. Providing adequate shelter during wet weather, avoiding sharing grooming equipment during outbreaks, and promptly treating any skin trauma reduce risk. ## Frequently asked questions **Is rain rot contagious?** Yes, it can spread between horses through direct contact or shared equipment, especially in wet conditions. **Is rain rot the same as rain scald?** Yes, the terms are often used interchangeably, though "rain scald" sometimes refers specifically to lesions on the back and rump. **Can rain rot affect the legs?** Yes, lesions can appear on the lower legs, though the classic presentation is along the dorsal midline. This information is for educational purposes only. Always consult with a licensed veterinarian for diagnosis and treatment of your horse.
Tufted, paintbrush-like scabs along the dorsal surface (back, croup, neck, withers); hair epilates easily in clumps with pus or crust on the underside; exposed skin underneath is pink, moist, and sometimes raw; lesions may spread to the face and legs in severe cases; usually not pruritic; worsens significantly during wet weather
Rain rot, also known as dermatophilosis, is a bacterial skin infection caused by *Dermatophilus congolensis*. Despite its common name, it is not a fungal infection. The organism thrives in warm, moist conditions and causes characteristic crusty, paintbrush-like scabs along the horse's back, neck, and rump. ## What it is *Dermatophilus congolensis* is an actinomycete bacterium that exists on the skin of many horses without causing disease. When the skin barrier is compromised by prolonged moisture, insect bites, or trauma, the organism invades the epidermis and causes superficial pustules that rupture and form thick crusts. The crusts contain embedded hairs and have a classic "paintbrush" appearance when lifted. ## Signs and symptoms - Tufted, paintbrush-like scabs along the dorsal surface (back, croup, neck, withers) - Hair epilates easily in clumps with pus or crust on the underside - Exposed skin underneath is pink, moist, and sometimes raw - Lesions may spread to the face and legs in severe cases - Usually not pruritic (not itchy), which helps distinguish it from other skin conditions - Worsens significantly during wet weather ## Causes and risk factors Rain rot develops when the skin remains wet for prolonged periods, especially in combination with skin trauma from insects or grooming. Risk factors include poor stable hygiene, horses kept outdoors in wet conditions without shelter, heavy feathering, and compromised immune function. The disease is more common in young horses and during periods of high rainfall. ## How it is diagnosed Diagnosis is usually straightforward based on the characteristic appearance and distribution of lesions. Microscopic examination of crusts can confirm the presence of *Dermatophilus* organisms (railroad track appearance of bacterial filaments). Bacterial culture is occasionally used in complicated cases. ## Treatment and management Treatment involves removing the crusts (after softening with oil or antimicrobial shampoo) and applying topical antibacterial agents. Keeping the horse dry is essential. In severe or widespread cases, systemic antibiotics may be required. Improving stable hygiene and providing shelter from prolonged rain help prevent recurrence. Most cases resolve within 1 to 3 weeks with appropriate treatment. ## When to call the vet Contact your veterinarian if the lesions are widespread, the horse is systemically ill, or the condition does not improve with basic topical treatment within a week or two. Severe cases can lead to secondary infections or significant discomfort. ## Prevention Prevention centers on keeping the horse as dry as possible and maintaining good skin hygiene. Providing adequate shelter during wet weather, avoiding sharing grooming equipment during outbreaks, and promptly treating any skin trauma reduce risk. ## Frequently asked questions **Is rain rot contagious?** Yes, it can spread between horses through direct contact or shared equipment, especially in wet conditions. **Is rain rot the same as rain scald?** Yes, the terms are often used interchangeably, though "rain scald" sometimes refers specifically to lesions on the back and rump. **Can rain rot affect the legs?** Yes, lesions can appear on the lower legs, though the classic presentation is along the dorsal midline. This information is for educational purposes only. Always consult with a licensed veterinarian for diagnosis and treatment of your horse.
Tufted, paintbrush-like scabs along the dorsal surface (back, croup, neck, withers); hair epilates easily in clumps with pus or crust on the underside; exposed skin underneath is pink, moist, and sometimes raw; lesions may spread to the face and legs in severe cases; usually not pruritic; worsens significantly during wet weather