Rain Rot in Horses 101: Causes, Symptoms and Treatment


Rain rot in horses is also called rain scald, dermatophilosis, and streptothricosis. No matter what it’s called, it’s an aggravating skin infection may cause extreme discomfort and hair loss in affected horses and ponies. Some horses and ponies are able to heal from rain rot on their own. However, some equines have been known to catch a secondary disease like Staphylococcal folliculitis and, sadly, die. Fortunately, there are many things a concerned horse owner can do to prevent and treat rain rot.

What is Rain Rot in Horses?

Rain rot is a skin infection that causes lesions, lumps, scabs, and hair loss. If the rain rot starts while the horse has its long winter coat, then patches will stick up like the hairs of a paintbrush before falling out. Lighter colored horses and ponies as well as those that have white markings like blazes or spots tend to be more prone to the bacteria that causes rain rot. Since rain rot in horses and ponies shares similar symptoms to ringworm and some other skin infections, it’s best to let a vet get a skin scraping to run tests to make sure the horse is suffering from rain rot and not something else.

What Causes Rain Rot in Horses?

Rain rot is caused by a bacterium called Dermatophilus congolensis. Normally, this bacterium lives peacefully on a healthy horse’s skin. When the horse is exposed to a lot of wetness, such as constant drenching rains, constant bites from insects, or high humidity, then the bacterium goes haywire and grows tentacle-like substances which cause the scabs, bumps, and hair loss of rain rot. Rain rot in horses is a common problem in the United Kingdom and in the Pacific Northwest because these are areas with a lot of rain.

Treatment Options Available for Rain Rot in Horses

The good news is that healthy horses tend to spontaneously recover once the weather turns hot and dry or cold and dry. However, not all horses and ponies are fortunate enough to be perfectly healthy. Also, biting insects like flies and mosquitoes can spread the bacterium that causes rain rot in horses, so treatment is recommended for all equines showing symptoms and then getting a positive diagnosis from a vet.

The main treatment is to groom the horse every day and bathe the horse in a medicated shampoo to help kill microbes. Usually these anti-microbial shampoos have ingredients like benzoyl peroxide which help kill the bacterium but also help remove dead skin and scabs. The scabs and hairless areas are intensely itchy. Be gentle when bathing the affected areas and removing scabs.

Attention: Horses and ponies with rain rot on the back or withers usually cannot be ridden because the weight of a rider and saddle is too painful for the horse.

In rare cases, an antibiotic shot may be needed:

  • if the horse or pony is in danger of getting a secondary infection;
  • if the rain rot is still persistent despite the shampoos and scab removal.

Veterinarians are more cautious in giving antibiotics now that many bacteria have developed immunity to many of them. An antibiotic can also upset the horse’s digestive system and cause diarrhea or other problems.

The prognosis for a horse or pony with rain rot is very good as long as the owner follows the veterinarian’s instructions. Many horses and ponies recover completely.

Prevention of Rain Rot in Horses

Fortunately, many things a horse owner does to keep their animals happy and healthy will also help in preventing rain rot. A good fly protection plan helps reduce the chance of getting rain rot from insect bites. Use fly spray during fly season and clean stalls every day. Have the manure piles removed from the property regularly so they do not attract flies. Keep the horse on a regular deworming schedule to prevent parasites which can soon make the animal too sick to fight off a skin infection.

Horses should be groomed every day and dried after getting wet. Use a sweat scraper to help remove excess wetness and help make drying out quicker. Horses left in pastures for long periods of time need weather-proof blankets to stay dry. These blankets need to be checked every day to make sure the horse has not dislodged the blankets or torn them. Horses also need at least a lean-to get out of the rain in a pasture if they are not stabled. All tack should be cleaned to prevent dirt and irritation that could eventually lead to rain rot. Make sure brushes and blankets are cleaned regularly.

If a horse or pony does get infected, isolate the animal from others to prevent infection. Use only one set of brushes and grooming items for an infected horse. Disinfect all brushes, hoof picks and other grooming equipment every day. This reduces the chances of the rain rot spreading to all horses and ponies in the stable.

In Conclusion

Rain rot or rain scald is a skin infection caused by a bacterium that causes intense itching and pain in a horse. Horses and ponies suffering from rain rot may be in too much pain to be ridden. Horses and ponies living in excessively rainy and humid areas need to be groomed properly every day to help prevent rain rot. Although some rain rot goes away on its own it should not be ignored.

Rain rot can lead to secondary infections which may be deadly. At the first signs of rain rot, call a vet. The vet will run skin scrape tests to make sure the cause is rain rot and not ringworm or another fungal infection. Treatment is usually bathing the affected areas with medicated shampoos but also may involve a round of antibiotics.

Photo: depositphotos.com.

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