“Rain Rot” or “Rain Scald” is a skin disease of horses commonly seen during periods of wet, cloudy weather. Many people mistakenly think it is a fungus, but it is caused by a bacterium called Dermatophilus congolensis. The bacteria enter the skin after it has been weakened by frequent wetting, and causes exudates (discharge of pus or serum) that mat the hairs together.
The result is areas of crusting over the back and rump, and occasionally the legs. The matted crusts are often painful if pulled off or if the horse is groomed, revealing pus and red, inflamed skin beneath the matted hairs. While mild cases of rain rot may resolve on their own within 2-4 weeks, some infections become severe.
Affected horses should be kept dry! Exposure to sunlight is beneficial for many skin problems including rain rot. Medicated shampoos can be used once or twice weekly, and topical antibacterial sprays or ointments can be helpful. Scabs should not be picked off, but gentle brushing with a soft brush or flexible rubber curry may help loosen them, if it does not cause discomfort to the horse. Systemic antibiotics are often needed to cure the infection that does not resolve on its own.
“Scratches,” “dew poisoning,” “mud fever,” “cracked heels,” and “grassy heel” are all names for the skin condition more correctly called pastern dermatitis. Scratches causes redness, pain, crusting scabs, and in severe cases swelling, lameness and cracking of the skin in the heel, pastern and fetlock area of the leg. Scratches commonly occurs in wet conditions and is more prevalent in horses with white leg hair and consequently pink skin.
Contact irritants and allergens such as long or stubbly pasture grass, mud, pollen and weeds irritate the skin and cause inflammation. Secondary infections can be bacterial, viral, parasitic, and fungal or a combination of these.The cornerstone of treatment of scratches consists of keeping the skin clean and dry! Long hair around affected areas should be trimmed or clipped. Medicated shampoos or soaps (benzoyl peroxide, chlorhexidine, providone iodine) can be used once or twice weekly. Zinc oxide creams (diaper rash creams) can be used as a moisture barrier.
For more severe cases, antibiotic-corticosteroid creams or ointments should be used. Systemic antibiotics, anti inflammatories, and antihistamines may be needed, especially for horses that experience limb swelling or lameness.