You run your hand across your horse's back and feel something that shouldn't be there.
Small bumps. Crusty patches. Maybe a few tufts of hair come away in your hand with a scab attached.
After weeks of rain, humidity or a constantly damp coat, there's a good chance rain rot may be to blame.
Rain rot is a common skin condition in horses, particularly during periods of wet, humid weather. But despite its name—and its sometimes fungus-like appearance—rain rot isn't caused by a fungus.
It's a bacterial skin infection.
And moisture creates exactly the environment it needs to become a problem.
What Is Rain Rot in Horses?
Rain rot, also called rain scald or dermatophilosis, is an infection of the outer layers of the skin caused by the bacterium Dermatophilus congolensis.
The bacteria can sometimes exist on the skin without causing obvious problems. Trouble begins when the skin's natural protective barrier becomes compromised—especially when it remains wet for extended periods.
Prolonged rain, humidity and a constantly damp coat soften the skin and create conditions that allow the bacteria to become active and spread.
That's why outbreaks are especially common during rainy seasons and in horses that spend long periods outside without an opportunity to completely dry.
What Does Rain Rot Look Like on a Horse?
Rain rot often feels noticeable before it looks dramatic.
Early on, you may feel small raised bumps beneath the coat. As the infection progresses, hair can become matted together in little tufts.
Those tufts may eventually lift away with crusts or scabs attached at the base—a characteristic appearance sometimes described as "paintbrush lesions."
Common signs of rain rot in horses include:
- Small raised bumps beneath the coat
- Crusty or scabby skin
- Tufts of matted hair
- Hair that pulls away with a scab attached
- Areas of hair loss
- Tender or painful skin
- Occasional discharge beneath larger scabs
- Lesions across the back, rump, neck or other areas exposed to moisture
Itching can occur, but unlike sweet itch, severe itching isn't necessarily the hallmark of rain rot. Some horses are much more tender or painful than itchy.
Where Does Rain Rot Usually Show Up?
Think about the places rain lands and moisture sits.
Rain rot commonly develops along the horse's:
- Back
- Topline
- Rump
- Neck
- Shoulders
It can also occur on the lower legs when they remain wet or muddy for prolonged periods.
Horses with thick coats may be particularly susceptible because moisture can become trapped close to the skin long after the surface of the coat appears dry.
What Causes Rain Rot in Horses?
The bacteria are the cause of the infection, but moisture is often what opens the door.
Several factors can make a horse more susceptible.
Prolonged Wet Weather
Weeks of rain and humidity are almost the perfect setup for rain rot.
Continually wet skin becomes softer and more vulnerable, allowing bacteria to penetrate the outer protective barrier.
A Coat That Never Fully Dries
A horse doesn't necessarily need to be standing in the rain all day.
Sweat trapped beneath blankets, thick winter coats, poorly ventilated coverings and repeated bathing without adequate drying can all keep moisture against the skin.
Skin Damage
Tiny breaks in the skin can make it easier for bacteria to establish an infection.
Insects, rubbing, scratches and other minor skin trauma can all contribute.
Reduced Natural Defenses
Young horses and animals with weakened immune systems appear to be more susceptible to dermatophilosis.
That's one reason we like to look beyond the surface when a horse repeatedly struggles with skin issues.
Is Rain Rot Contagious?
It can spread from horse to horse.
The bacteria can be transferred through direct contact or contaminated items such as:
- Brushes
- Curry combs
- Blankets
- Saddle pads
- Tack
- Clippers
- Barn equipment
Biting insects may also mechanically carry the organism from an infected animal to another horse.
If one horse in your barn has rain rot, don't share grooming supplies or blankets until the issue has cleared and the equipment has been thoroughly cleaned.
There is also a rare potential for transmission to people, so wearing gloves while handling active lesions and washing your hands afterward is a smart precaution.
How Do You Treat Rain Rot in Horses?
There are two important pieces to dealing with rain rot:
Address the infection and eliminate the wet environment that allowed it to thrive.
1. Get the Horse Dry
This sounds simple, but it's one of the most important parts of managing rain rot.
Move the horse somewhere the coat and skin can remain dry. Improve shelter, airflow and bedding conditions when necessary.
If blankets are contributing to trapped moisture, make sure you're not repeatedly putting a damp blanket over a damp horse.
Dry conditions alone can make a significant difference, and uncomplicated cases may improve as wet weather resolves.
2. Don't Just Rip Off the Scabs
Those crusts can be tender.
Veterinary treatment often involves gently softening or soaking affected areas before removing loose crusts, rather than aggressively picking or scraping them off dry.
Your veterinarian may recommend an antimicrobial shampoo or other topical treatment depending on the severity of the infection. More significant or widespread infections can require prescription antibiotics.
3. Clean Anything That Touches the Horse
Brushes, blankets, saddle pads and other equipment can potentially harbor infectious material.
Separate the affected horse's supplies and clean them thoroughly before using them again.
This is especially important in barns where grooming tools are routinely shared between horses.
4. Watch for Severe or Persistent Cases
A mild patch of rain rot and an extensive, painful bacterial infection aren't the same thing.
Call your veterinarian if:
- A large portion of the body is affected
- The skin is extremely painful
- There is significant swelling or discharge
- Lesions involve the lower legs and affect movement
- Your horse is losing condition
- The problem continues despite getting the horse dry
- You're not certain it's actually rain rot
Several other conditions—including ringworm and other forms of dermatitis—can resemble rain rot, so persistent skin disease deserves a proper diagnosis.
Rain Rot vs. Ringworm: What's the Difference?
They're easy to confuse, but they're not the same condition.
Rain rot is bacterial. Ringworm is fungal.
Rain rot typically produces crusty, matted tufts of hair and often appears across areas exposed to prolonged moisture.
Ringworm commonly produces circular areas of hair loss with scaling or broken hairs and frequently develops around areas where tack contacts the horse.
Both can spread through contaminated grooming equipment, which is another reason not to assume every scabby or bald patch is "just rain rot."
Supporting Your Horse From the Inside
Topical care and proper veterinary treatment address what's happening on the skin.
At Silver Lining Herbs, we also believe healthy skin starts with supporting the systems responsible for the body's natural defenses.
INF-X for Horses
Because rain rot is associated with a bacterial challenge, INF-X for Horses is one of the products we commonly reach for as nutritional support.
INF-X combines herbs selected to support healthy immune function and the body's normal defenses during bacterial, viral and fungal challenges. Horse owners have also reported using INF-X while supporting horses dealing with rain rot and other skin challenges.
It's important to remember that an herbal supplement does not replace appropriate treatment for a bacterial infection. A horse with significant dermatophilosis may still require veterinary-directed topical or systemic antimicrobial treatment.
Immune Support for Horses
Skin is one of the body's largest protective barriers, and immune health plays an important role in keeping that barrier functioning normally.
Immune Support for Horses provides nutritional support for normal immune function, normal detoxification processes, and healthy skin and coat—making it another option to consider for horses that seem particularly susceptible to environmental skin challenges.
How to Prevent Rain Rot From Coming Back
If your horse seems to get rain rot every time the forecast turns soggy, prevention is worth the effort.
Focus on keeping the skin's natural barrier intact and reducing prolonged moisture.
- Provide adequate shelter during extended rainy periods.
- Allow sweaty or wet horses to dry completely.
- Don't trap moisture beneath blankets.
- Groom regularly so you notice skin changes early.
- Wash and completely dry blankets and saddle pads.
- Avoid sharing grooming equipment between affected horses.
- Keep muddy areas around shelters and gates under control when possible.
- Maintain good overall nutrition and immune health.
- Stay on top of biting insects that may damage the skin or contribute to spread.
The goal isn't to keep a horse from ever getting wet.
It's to prevent the skin from remaining chronically wet and compromised.
The Bottom Line on Rain Rot in Horses
The rain itself doesn't actually cause rain rot.
Rain creates the conditions that allow Dermatophilus congolensis to take advantage of weakened, waterlogged skin.
Once you recognize those telltale bumps, crusts, and tufts of hair, think about the whole picture:
Get the horse dry. Protect the skin. Control the infection. Clean the environment. Support the horse.
Many uncomplicated cases respond well once the horse is kept dry and proper skin care begins. But painful, widespread, or persistent cases deserve veterinary attention—especially because not every crusty skin condition is rain rot.
Supporting a Horse With Rain Rot?
Explore INF-X for Horses for nutritional immune support during bacterial, viral, and fungal challenges, or add Immune Support for Horses to help maintain normal immune function and healthy skin and coat.
Always consult your veterinarian for diagnosis and treatment of persistent, painful or widespread skin infections.