What does Rain Scald or Rain Rot look like?:
An indication that your horse may be getting rain rot is the presence of fine grey dander when you brush its coat. Rain scald appears as scurfy patches on a horse’s or pony’s back, shoulders and haunches. The hair may be ‘staring’ or matted in small areas. The hair grows through the patches at first and the scald may not be apparent until you feel the rises on the skin. Pull away the hair and the scurf will lift. The skin beneath will appear raw and oozing. If left untreated infection can set in.
What Causes Rain Rot?:
Rain scald occurs when horses (who are often, but not necessarily in poor condition) are exposed to wet weather and muddy conditions. If the horse’s or pony’s skin stays damp and dirty for long periods of time it becomes infected by bacterium. Sometimes, within a herd managed in exactly the same manner, some horses will be affected and some not.
The same conditions and bacteria cause grease heel.
How Can I Avoid It?:
Keeping your horse clean and dry will help prevent rain scald. During wet weather make sure that your horse has shelter, or is wearing a rainproof (and breathable) sheet or blanket. Some horses will not use a run-in shed and need to be brought in to dry out completely. If the weather is very cold, a rain sheet may not be the best choice as it will keep your horse dry, but it prevents piloerection or what we call 'goose bumps' that help the horse stay warm. It would be better to keep your horse stabled or put on a lined winter rug that can help the horse stay warm without its natural defenses. Some people rinse that back area with a vinegar solution to keep the skin acidic. I've not tried this so can't attest to it's effectiveness. If the skin is already broken however, vinegar will sting, so use caution and common sense.
How Can I Treat the Problem?:
Gently brush away and clip loose and long hair. (Sterilize your scissors or clippers before and after use.) Wash the affected areas with a mild antiseptic like betadine soap. Apply a topical such as a zinc oxide cream or antiseptic ointment. There are several topical lotions, liquids and creams available at tack shops.
During treatment the horse will have to be kept in dry, clean conditions. It could take several weeks for the skin to heal.
If the skin is infected, does not respond to home treatment within a few days, or is badly cracked, consult your veterinarian. Continue to keep the horse dry and clean to prevent a recurrence.
Any brushes or equipment used on a horse with rain scald should be sterilized before use on another horse. It may be easier to keep a separate set of brushes for each horse being treated to prevent cross-contamination.
You may have to wait to ride or drive your horse as putting a saddle or harness over top of broken skin will be uncomfortable for your horse.