The name “rain rot” is one of those terms that can be easily misunderstood. Although named for rain, rain doesn’t cause rain rot, just as worms don’t cause ringworm. There are three main reasons why horses get rain rot, and if your horse develops it every time the weather turns wet and humid, you might want to blame it on the rain, but you would likely be mistaken.
Rain rot, also known as rain scald or dermatophilosis, is a bacterial skin infection associated with Dermatophilus congolensis. The bacteria can be present without causing any obvious problems. Trouble develops when conditions allow the organism to get past the skin’s natural defenses and multiply.
Understanding the true cause of rain rot will help you do more than simply treat rain rot after it develops. It can help you figure out why your horse is getting it in the first place.
The Three Pieces of the Rain Rot Puzzle
When you think about the formation of rain rot, consider it a problem that only develops when several things work together.
1. Moisture
Prolonged moisture softens the outer layers of the skin and creates an environment where the bacteria responsible for rain rot can become active. Moisture doesn’t necessarily have to be caused by rain or standing outside in it. It can come from high humidity, sweat trapped beneath blankets or tack, frequent bathing without adequate drying, or a consistently damp coat.
That is why rain rot got its name. It is more common during hot and humid conditions. But moisture itself is not the culprit; it is just a contributing factor. If rain alone were the cause, every horse standing in the same wet pasture would develop it, and they don’t.
2. Damage to the Skin Barrier
Healthy skin is your horse’s first line of defense against rain rot. When the protective layer becomes damaged, bacteria have an easier opportunity to invade. Sometimes the damage is obvious, such as a cut or scrape. Other times, it can be unnoticeable.
Insect bites are one of the most common reasons for damage. Flies, mosquitoes, gnats and other insects bite the skin. The horse will typically respond by rubbing or scratching the irritated area, creating more damage.
Friction can do the same.
If you have an improperly fitting piece of equipment that repeatedly rubs the same area, sweat and moisture trapped beneath the equipment can often compound the problem and lead to issues.
Therefore, noticing rain rot is only half of the battle. If you see it in a particular location, that will give you insight and clues into why your horse might be developing it to begin with.
3. How Well the Horse’s Natural Defenses Are Working
Of all the causes of rain rot, the one that is commonly discussed least is why two horses can live in the same pasture and conditions, experience the same rain and humidity, and encounter the same insects, yet one develops rain rot and the other does not.
Why?
The underlying condition and health of the horse matter.
Skin isn’t simply something that covers the organs; it is an organ itself and an important part of the body’s defense system. Nutrition, general health, stress and other underlying factors can affect the health of the skin and its ability to respond when that protective barrier is challenged.
That doesn’t necessarily mean that every horse with rain rot has a compromised immune system or nutritional deficiency, but repeated infections should make you pause to consider what else is contributing.
If Rain Rot Keeps Coming Back, Ask Why
Treating visible skin conditions is important, but simply treating them after the fact could be the real problem. If your horse develops rain rot over and over again, you might be missing the real issues and overlooking what needs to be done to prevent it from coming back again.
It’s important to start looking for patterns.
Ask yourself what conditions led to the irritation and problem. Does it appear at a specific time? Is it connected to a pest control issue, a rubbing blanket, or is your horse’s nutrition lacking? You have to take a good look at the entire picture rather than assuming you know what the problem is.
Nutrition Matters to Healthy Skin
Healthy skin has to be built from the inside out.
Things like adequate protein, essential fatty acids, vitamins, minerals, and access to clean water are all important and contribute to normal skin and coat health. A horse whose nutritional needs aren’t being met may have a skin barrier that isn’t functioning as effectively as it should or needs to.
That doesn’t mean you should run out to buy supplements.
It means you have to take a hard look at your nutrition over time to see if you can pinpoint what might be lacking to cause skin problems. Look at your horse’s entire diet and talk with your veterinarian or equine nutrition professional rather than just trying to correct the problem using individual supplements that may or may not be the issue.
Don’t Forget About Stress and Overall Health
Stress is not good for any organism, horses included. Stress can affect horses physically as well as behaviorally.
Travel, illness, pain, changes in the environment, inadequate nutrition and other stressors can influence overall health. An underlying medical condition can also make horses more susceptible to infections.
A single case of rain rot during an exceptionally hot and humid spell doesn’t necessarily indicate that there is a larger health concern looming. But a horse that repeatedly gets rain rot despite good environmental management deserves a closer look.
Recurring or severe skin problems are worth addressing with your veterinarian, especially if you notice other things like weight loss, poor coat quality, lethargy, slow healing, fevers, or any other signs that your horse might not be at its best.
Stop Blaming the Rain
That song might have been a hit at one time, but rain rot can often distract owners from what is really happening. A better way to think about rain rot is to consider the relationship between moisture, the integrity of your horse’s skin barrier, and their ability to repair the skin barrier against insult.
When rain rot happens once, treat the condition and improve the environment.
If it keeps happening, start asking why.
Preventative care is always better for your horse, so considering things like nutrition, insects, tack and blanket fit, friction, and external sources plus internal ones is the best way to keep your horse’s health intact both inside and out.
At Purely Equines, we believe good horse care isn’t simply about finding something to put on a problem after it appears. It’s about understanding your horse well enough to recognize the conditions that allow problems to develop before they do.
Because sometimes rain rot isn’t telling you that it’s been raining; it’s telling you to take a closer look at your horse’s health.
If you are having a hard time with rain rot, our Derma-Soothe Shampoo, Coat Shield, and other products are designed to help restore your horse’s natural defenses so it can fight the way it should. Check them out today.
