You run your hand over your horse’s rump and feel a couple of little bumps buried in the coat. Maybe it’s dirt. Maybe something got caught in there. You curry over them, a few flakes come loose and you don’t think much of it.
By tomorrow, there are twice as many. A day later, half the rump feels bumpy and your previously agreeable horse would really prefer you keep that curry comb to yourself.
Rain rot has arrived.
After years of working with horses in South Florida, I’d estimate that at least half of the horses I’ve cared for have developed some degree of mild rain rot at one point or another. Some cases amount to a handful of crusty bumps that disappear almost as quickly as they arrived. Others spread across the rump and back, taking patches of hair with them and leaving sore, irritated skin underneath.
The good news is that rain rot is usually very manageable, especially when it’s caught early. The less exciting news is that there really isn’t a magic potion for it. In my experience, the most reliable treatment has always been much less glamorous: get the skin clean, use an appropriate antimicrobial product, get the horse completely dry and most importantly, keep them that way long enough for the skin to recover.
What is rain rot in horses?
Rain rot is the common name for dermatophilosis, a skin infection caused by Dermatophilus congolensis. Despite the collection of antifungal products that tend to get thrown at it in barns, rain rot itself is not a fungal infection. D. congolensis is an actinomycete bacterium that causes a superficial, crusting infection of the skin.
The organism itself isn’t the whole story. Moisture and damage to the normal skin barrier play important roles in allowing infection to develop. Prolonged rain, high humidity and warm conditions are all associated with dermatophilosis, which explains why those of us caring for horses in hot, humid climates become particularly familiar with it.
That also explains why the name “rain rot” is actually pretty appropriate. A horse getting caught in one rain shower doesn’t automatically mean he’ll wake up covered in crusts but repeatedly wet skin that stays damp creates a much more favorable environment for the infection.
What does rain rot look like?
One of the first signs of rain rot may be something you notice with your hands before you ever see it.
When I’m grooming a horse, I sometimes notice that an area of skin feels slightly warmer than the surrounding skin. Soon after, I’ll find one or two little raised bumps beneath the hair. They can be easy to mistake for dirt or debris caught in the coat.
As the infection progresses, those isolated bumps can multiply surprisingly quickly.
The classic rain rot lesion is a crust or scab with hair attached to it. When the crust releases, the hair often comes with it and leaves a small bald patch underneath. With enough lesions close together, those little bald spots can eventually turn into fairly substantial areas of hair loss. This crusting and clumping of hair is a characteristic presentation of equine dermatophilosis.
In the horses I’ve worked with, the rump is by far the most common place I find it, followed by the back. I’ve also seen it on the legs. On the sides of the face, I tend to notice hair loss more than the thick, obvious crusting I see over the rump and topline. The forehead area is another commonly affected location. I can’t remember personally dealing with a notable case on the neck, although rain rot certainly isn’t restricted to the areas where I happen to see it most often.
That is an important caveat. My experience tells you what I personally encounter in the barn, not every place dermatophilosis can occur.
Is rain rot painful?
It certainly can be.
A horse with a few early lesions may barely care that you’re touching them. Once an area becomes heavily crusted and inflamed, the reaction can be very different. Horses that normally love being groomed may suddenly pin their ears, flinch or move away when you run a curry comb across the affected area.
Veterinary guidance also recognizes equine dermatophilosis lesions as painful, which is one reason treatment is recommended rather than simply waiting indefinitely for the infection to resolve.
This is also where the traditional instruction to “get all the scabs off” needs a little common sense attached to it.
The crusts contain infectious material and removing them is part of treatment but that doesn’t mean attacking a painful horse with a curry comb until every single bump is gone. Veterinary recommendations call for gently soaking and removing the crusts.
If a crust is firmly attached and removing it is obviously painful, soften it first. With bathing and treatment, many begin to release much more easily. There is a big difference between removing loose, softened crusts and ripping firmly attached scabs away from inflamed skin.
Your horse will make that quite clear, listen to him.
How I treat rain rot
For uncomplicated cases that I catch early, my approach is simple.
I start with an antimicrobial bath. I’ve used products such as EQyss Micro-Tek and E3 antibacterial/antifungal shampoo over the years, following the product directions and allowing the shampoo to sit on the skin for its recommended contact time before rinsing thoroughly.
Chlorhexidine also has veterinary support for dermatophilosis. The Merck Veterinary Manual identifies 2–4% chlorhexidine antimicrobial shampoo as an effective adjunctive topical treatment.
During the bath, I work very gently. As the crusts soften, I remove what releases reasonably easily rather than making it my mission to leave the horse completely scab-free in one afternoon.
Then comes the part I consider just as important as the shampoo:
get the horse completely dry.
I towel dry thoroughly and when possible, let the horse stand in front of a fan or hand walk in the sun until I’m confident the coat and skin are actually dry.
A bath is temporary moisture with a specific purpose. Leaving a horse damp for hours afterward is something else entirely.
Whatever you do, I would not put a fly sheet, turnout sheet or blanket back onto a horse whose coat is still damp after bathing. You’re putting a layer over the exact warm, wet environment you’re trying to get away from.
Once everything is dry, I will sometimes work a small amount of Coat Defense powder down to the skin. That’s part of my own management routine rather than a treatment I’m presenting as proven to cure dermatophilosis. The antimicrobial cleansing, thorough drying and environmental management are doing the heavy lifting.
You have to change the environment too
This is probably the biggest lesson I’ve learned from dealing with rain rot.
You can bathe the horse, treat the skin and dry him beautifully but if you send him straight back into the same wet conditions every night, you’re making the job considerably harder.
Successful treatment requires addressing the environmental conditions that allowed the infection to develop. Veterinary guidance specifically emphasizes keeping affected horses dry and preventing chronic moisture exposure.
That doesn’t necessarily mean a horse needs to spend days locked in a stall.
If the paddocks are soaked or storms are rolling through, you may substitute turnout in a covered or indoor arena for a day or two. Depending on the horse and the facility, exercise might come from hand walking, a treadmill or a hot walker instead. The point is to give the skin a chance to recover without repeatedly soaking it again.
Sometimes getting ahead of rain rot means temporarily changing the horse’s routine while his body finishes the job.
My own horse, Simon, is a good example. Rain rot thankfully isn’t one of his chronic skin problems but he’s still had it several times over the 16 years I’ve owned him. It has almost always followed the same pattern: rainy season, overnight turnout and an unexpected shower while he’s wearing a fly sheet.
The barn can watch the forecast carefully and keep him in when significant rain is expected but anyone who has lived around Florida weather knows how that goes. Sometimes a little 3 a.m. weather system appears anyway.
Wet horse plus damp fly sheet plus warm weather is a combination I try very hard to avoid.
Should you clip a horse with rain rot?
This is one of those questions where timing makes an enormous difference.
Having a clipped horse before a skin problem develops can make management considerably easier. Short hair makes it easier to see the skin, clean affected areas, get shampoo where it needs to go and crucially, get and keep the horse dry.
Once a horse is already covered in raised, painful crusts, I generally consider my window of opportunity to clip comfortably to have passed.
Clipper blades can catch the crusts and pull them away before they’re ready to release. Scabs and debris also end up in the blades while you’re trying to run clippers across skin that’s already irritated and sore.
Veterinary guidance notes that clipping may sometimes be necessary in the management of dermatophilosis. In practice, I think the condition of the skin matters enormously. There’s a difference between carefully removing excess hair where needed and trying to body clip straight through an established, painful outbreak.
Is rain rot contagious?
Yes, and this is where barn management deserves more attention than it gets.
Clinically affected horses can spread infectious material and veterinary recommendations include isolating affected animals when appropriate as well as paying careful attention to the cleanliness of tack, blankets, grooming tools and other equipment.
I grew up in a lesson barn where every horse had his own brushes and we disinfected grooming tools at the end of each day and that habit stuck with me.
What did not stick with me is the communal sweat scraper.
Almost every barn I’ve worked in has had one or two sweat scrapers hanging in the wash stall for everybody. Some barns go a step further and provide a communal bath bucket stocked with rubber scrub gloves, curries and other bathing supplies. I completely understand the sentiment. It’s convenient and looks beautifully organized.
It’s also an excellent way to move whatever was on Horse A directly onto Horse B.
Ideally, each horse should have his own grooming and bathing equipment (I’m looking at you, multi-horse owners). Brushes, curries and sweat scrapers are inexpensive insurance compared to treating a barn full of skin disease.
Saddle pads, fly sheets and blankets deserve the same consideration. Equipment that has come into contact with an affected coat should be cleaned appropriately rather than passed along to another horse.
So please, for the love of horses everywhere, retire the communal sweat scraper.
One other reason to take hygiene seriously: dermatophilosis is considered zoonotic, meaning it can occasionally infect people. Human cases are uncommon but I’d still wear gloves when handling affected crusts or heavily involved skin and wash my hands well afterward.
What about MTG, Listerine and all the other rain rot remedies?
If you’ve been around horses long enough, someone has a DIY rain rot cure.
I’ve tried plenty of them.
As a teenager I experimented much more freely with barn remedies, including Listerine (Sorry, Simon). There was also a period when MTG seemed to be recommended for practically every skin problem a horse could develop. I’ve used that too.
These days, I don’t reach for either.
I’ve found MTG to be a greasy, smelly mess that can be irritating and I haven’t seen enough benefit to justify coating already unhappy skin in it. The same basic problem applies to many of the heavy ointments, oils and concoctions I’ve tried. They make an enormous mess without producing a noticeable improvement over good antimicrobial cleansing, drying and environmental management.
I’m also much less interested now in the endless rotation of “magic” over the counter products.
Then there are the old-timer remedies.
Someone’s great-grandfather bred Tennessee Walkers and poured gasoline on rain rot and apparently it cleared right up.
Please stop.
Skin that’s already inflamed and painful does not need an improvised chemical experiment performed on it. The fact that something can kill microorganisms does not make it appropriate to put on damaged living tissue.
There are established topical antiseptics used for dermatophilosis, and chlorhexidine is among those supported in veterinary references. There’s very little reason to see how creative we can get with treatment.
How to prevent rain rot
If there’s one skin condition where I genuinely think prevention is easier than treatment, this is it.
You can’t control the weather but you can control quite a bit of what happens afterward.
Pay attention to horses that come in wet. Remove soaked sheets and blankets rather than leaving them sitting against the coat. Make sure a horse is completely dry after bathing before covering him again. Clean grooming equipment regularly and don’t share it between horses. Wash saddle pads, blankets and fly sheets regularly so you’re not repeatedly putting contaminated equipment against clean skin.
During stretches of wet weather, run your hands over the horse while grooming. Don’t just look.
Those first few tiny bumps are incredibly easy to miss visually, particularly in a dark or thick coat. Feeling two suspicious bumps today gives you a much better chance of intervening before you’re looking at what feels like hundreds of them tomorrow.
For horses I know are particularly prone to skin trouble, I also keep an appropriately prepared chlorhexidine spray on hand and pay close attention to suspicious areas before they turn into a full outbreak. What product and concentration is appropriate depends on what you’re using and how it’s labeled, so this isn’t an invitation to start mixing concentrated chlorhexidine by eye. Ask your vet what they recommend.
More than anything, though, dry skin is your friend.
When should you call the vet for rain rot?
I’ve been fortunate that none of the rain rot cases I’ve managed have progressed to the point that a horse needed systemic antibiotics. Catching outbreaks early and being fairly aggressive about changing the environment has worked well for me.
That doesn’t mean every case will be so simple.
Severe, generalized or chronic dermatophilosis may require systemic antimicrobial treatment. If your horse is extensively affected, particularly painful, systemically unwell or simply isn’t improving despite appropriate care, it’s time to involve your veterinarian.
I’d also call when the skin disease doesn’t behave the way you expect rain rot to behave.
Not every crusty skin condition on a horse is dermatophilosis. Dermatophyte infection, better known as ringworm, can also cause crusting and hair loss, among other differential diagnoses. D. congolensis can be identified from crust samples by cytology and PCR testing has also been studied as a diagnostic method in horses.
If you’ve been faithfully treating “rain rot” and nothing is changing, the answer may not be another bottle from the tack store, it may be finding out whether you’re actually treating rain rot in the first place.
The bottom line
Rain rot is one of those horse problems that can look impressively ugly without necessarily requiring a costly, complicated solution.
Catch it early. Treat the skin gently. Use an appropriate antimicrobial cleanser. Soften crusts rather than ripping them away. Dry the horse completely and change the wet conditions that helped the infection take hold. Keep grooming equipment clean and separate between horses.
Then give the skin some time to heal.
After years of experimenting with more rain rot remedies than I care to admit, I’ve become considerably less interested in finding the next miracle treatment. The boring answer has been far more dependable: clean, dry and don’t keep putting the horse back into the environment that caused the problem in the first place.
Sometimes good horse care really is that unexciting.
Sources
Merck Veterinary Manual. Dermatophilosis (“Rain Rot”) in Horses. Updated July 2026.
Merck Veterinary Manual. Dermatophilosis in Animals.
Merck Veterinary Manual. Antibacterials for Integumentary Disease in Animals.
Texas A&M School of Veterinary Medicine & Biomedical Sciences. Taking a Raincheck on Equine Rain Rot.
Frank LA, Kania SA, Weyant E. RT-qPCR for the diagnosis of dermatophilosis in horses. Veterinary Dermatology. 2016;27(5):431-e112.
Foster AP. et al. Common superficial and deep cutaneous bacterial infections in domestic animals: A review. Veterinary Pathology.