How to Treat Rain Rot on Horses

Jessica McDaniel
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What Causes Rain Rot

Rain rot is typically caused by a severe, untreated fungal infection called dermatophytic hypersensitivity. It is most commonly found in high-energy, fast-growing, young horses, and rarely appears in older animals. Rain rot occurs more frequently during spring and autumn due to a change of temperature and humidity levels.


Horses typically exhibit hair loss, scaly patches, inflamed skin lesions, crusting, and hair discoloration due to rain rot. Dermatophytic hypersensitivity is found on the head, shoulders, and legs of horses. Rain rot on the body typically appears near the head of the horse and extends down the back.

Rain Rot

If left untreated, rain rot causes continued hair loss, discoloration, scaly patches, crusty lesions, thinning of the hair coat, and scarring.

How Rain Rot in Horses Happens

Rain rot in horses is a skin condition that is characterized by a rain-like pattern of hair loss. It is most common in horses that have skin folds, such as the Arabian horses. The skin and subcutaneous tissue become raw from the constant irritation of licking and rubbing. This condition occurs when the animal is kept in muddy and dirty environments. It is also called mud fever, wet eczema, and dirty-leg disease. It affects all types of horses and colts, but it is fatal if left untreated.

Because mud fever is caused by bad environmental conditions, it is a good idea to remove the animal from the dirty environment and provide it with high quality nutrition. The goal is to keep the immune system working well and to avoid stress. Although no cure can prevent the effects of this problem, there are treatments that can effectively manage it.

If you notice grey, brown or black discoloration on the skin surface around the lower limb and under the belly flap, your horse has mud fever. Check the horse's legs and if you discover the hair is falling out and there are some open wounds, then you must take immediate action.

Rain Rot Causes

Rainrot begins with exposure to poor quality weather conditions. Rainy and wet conditions, especially wet, humid conditions promote bacterial keratitis which is the infection responsible for causing rain rot. Gut infections, external parasitic infections, and injury can also play a role in weather rot.

During warm weather, the skin can be irritated by fungus as well. The fungus called piedra, or white rain rot, is normally a freshwater infection that occurs during wet weather. Rain rot can develop due to fungal infections such as piedra or bacterial infections such as whirling disease that can then turn into piedra infections.

Rain Rot in Horses: Diagnosis

If your horse suddenly develops an itchy, scaly, red rash between the shoulder blades that is usually hot and tender, and there is no sign of external fleas, you could be dealing with rain rot.

Rain rot is caused by bacteria called Streptococcus equi subspecies zooepidemicus. S. equi z.e. is transmitted via horses through water and putrid bedding. Rain rot is most common among young horses who have not had a chance to develop a loyal gut flora.

Rain rot is highly contagious and like the name suggests, is common in wet, humid areas. It can be transmitted through contaminated clothing or tack, wet pastures, and when you handle an infected horse. It can also be transmitted to pastures, nearby water, and your barn exterior.

What it looks like

Rain rot in horses is a fungal skin infection that results in hair loss and a raw, irritated skin with sores. The infection can be caused by bacteria, but it is more commonly caused by fungus. The disease strikes horses’ hooves and lower legs, with the condition most often appearing during rainy or muddy conditions.

One main symptom of rain rot is a peppery or garlic smell coming from the horse’s feet. Other symptoms include:

  • leathery looking skin
  • overgrowth of the hoof horny tissue
  • scabs on the hooves

You can tell if your horse has rain rot if it is running a fever, has swollen lymph nodes, has sores on its legs, and/or has a severe case of rain rot with patches of his skin rotting off.

As with any disease, it is important to consult your veterinarian. His or her appropriate course of action will depend on the severity and type of the rain rot.

How Your Horse May Act

Rain rot can be easily mistaken for another skin disease called sweet itch. While they both have similar symptoms, sweet itch is caused by a type of fungus. Whereas, rain rot is caused by bacteria. Symptoms of sweet itch are usually flaky skin and exudate. Symptoms of rain rot include a buildup of exudate, which may have a foul odor.

If your horse is scratching or biting at an area on his body, this may be a sign that he is suffering from sweet itch or rain rot. However, if he’s not scratching or biting, it’s possible that he could be experiencing rain rot while not showing any signs of it.

Your horse may not be acting worse for weather. If you’re not sure of what skin disease he is experiencing, the best thing for you to do is make sure he has access to plenty of cool water. Give him a bath if you can and keep his environment cool to help prevent skin disease.

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Official Diagnosis

Rain rot is usually caused by the fungus Rhodotorula. When the coat is compromised or damaged, it provides an open entrance for the bacteria to take hold. This can be caused by conditions including: mud, wet conditions, winter weather, horse parasites, cuts, abrasions, or improperly fitting tack.

The lymph system is what will ultimately be affected. Lymph nodes, which are in and around the joints, will swell. You may also notice swellings due to the inflammation of the lymphatic vessels in the armpits, genitals, and legs.

The tissue starts to break down as a result of the infection. Your horse may also have sensitivity to touch in these areas as a result.

When determining if your horse has rain rot, you want to rule out other causes first. This will include:

  • Elevated body temperature
  • Discharge from the affected area
  • Pain in the armpit, joints, or leg

It’s important to also determine whether or not the affected area has turned into a case of thrush or fungus. Though many horse owners will assume rain rot and thrush are the same thing, they are actually two different types of infections

Thrush is caused by a fungus that affects the skin like ringworm, and can easily spread. It most often affected the hooves of the horse.

Rain Rot Treatment For Horses

Rain rot is a skin condition common to horses that live in humid climates. Rain rot is caused by a fungus that lives in the soil. In its early stages, rain rot can be mistaken for mud and followed by an "acne" like skin condition. As the condition progresses, the skin begins to break down and form open wounds.

Rain rot is the most common type of fungal infection of the skin in horses and has a large impact on a horse’s health and ability to live a quality life.

Rain rot will not affect your horse’s lifespan but is an uncomfortable condition that causes a lot of pain and suffering.

Rain Rot Treatment For Horses Your horse will become infested with rain rot when it comes in contact with several different types of fungus… or when it’s immune system is wiped out from conditions like equine infectious anemia or Lyme’s disease.

Two types of skin fungus that cause rain rot are:

Dermatophilous Fungus

Dermatophilous fungus is actually the most common fungal disease in the world. It lives in soils and is found everywhere. Horses that live in a wet, humid climate or live on a diet high in grain are more susceptible to this fungus.

Environmental Fungus


The most important aspect of treating rain rot is to get it diagnosed accurately, so any medications you use will be helpful. Your veterinarian will need to examine the horse, so he or she can get a good look at the affected area. The client should come prepared with a photo of the affected area, if possible. It will be helpful to the veterinarian if you can describe the build-up of the skin and where it is located ¨C front or back, side or stomach.

Preventing the spread of the fungus is equally as important as treating it, so it is necessary to thoroughly clean and dry the horse after each exposure to rain, and apply medication to the affected areas. Your veterinarian will prescribe medication that is specifically formulated for the treatment of rain rot.

There are different products used to prevent rain rot, which will be prescribed by your veterinarian. One of the most common such products is kelp and vitamin E. Some of the treatment options for rain rot include oral medications to address any fungal or bacterial infections and topical disinfectants that you apply to affected areas. Some of these topical disinfectants will help prevent wound infections too.

Home Treatment

Rain rot is a condition that affects horses after being exposed to heavy rain. Rain rot can be caused by a bacterial or fungal infection.

Rain rot typically affects the head. If your horse has rain rot, you may see hair loss on the forehead and muzzle as well as on the ears, eyelids, and nostrils. Rain rot may also cause the hair on these areas to look "dirty"–soiled with brownish stains.

Since rain rot is primarily caused by bad weather, there's not much you can do to prevent it. If your horse has mild rain rot, you can try bathing the affected areas with a solution of mild shampoo and warm water.

Bathe your horse regularly, and ensure that he gets lots of dry-time after each bath. He may also benefit from a deep-conditioner, which will help to restore his coat and prevent further damage.

Listen to Your Veterinarian

It’s always best to listen to your veterinarian’s advice, for help in determining your horse’s condition. While you may have your own opinions about how your horse is feeling, the veterinarian’s opinion should be taken into consideration when making decisions.

Below are some common questions that vets will ask you about your horse:

  • How has your horse been recently? Has he experienced any other symptoms besides rain rot?
  • What was your horse doing in the weeks just prior to developing rain rot? Was he in a drought, and if so, was rain water offered?
  • What has your horse’s diet consisted of the last several weeks? Does he seem to have any allergies to any feed or treats he may have received?
  • Has your horse’s level of care changed significantly in any way recently?
  • Has your horse groomed frequently and taken care of his feet?
  • Has your horse been drinking excessively or eating hay on the ground?
  • Has your horse had a change of pasture and access to water?
  • Has anyone started a new job recently caring for your horse?
  • Has anyone in your barn experienced illness?
  • Has anyone in your barn left?

Rain Rot in Horses: Prevention

This article focuses mainly on the symptoms of rain wounds, how to treat them using an inexpensive treatment and how to prevent them from re-occurring with the use of fly sheets.

It is important to remember that rain rot is not the same as mud fever. Although both horses and donkeys can get mud fever, due to an allergy to fungus in the soil, rain rot is the official name used by veterinarians for rain wounds. They are caused by a viral infection and are common in horses that are kept out in fields that take long to dry. They tend to develop after periods of rain or as a reaction to the dirt from the wet ground.


Getting your horse to a vet as soon as possible to have the wound properly checked is the most important step in treating rain wounds. If you catch it early enough, your vet may be able to treat it with antibiotics. Unfortunately, it is often too late to treat the rain wounds with antibiotics by the time we notice them.

Treatment obviously involves cleaning the wound, washing it with Dettol or another antiseptic wash and then covering it in a stable bandage. It is important to keep the bandage clean by changing it at least twice a day.

Prevent Rain Rot if You Can! If Not, Treat it Immediately

The main cause of rain rot is a fungus called Piedra. Rain rot is the type of fungus that grows on the surface of the skin. It is caused by the fungus that attaches to the skin, which then breaks the skin and creates the unsightly, oozing sores. Rain rot can be transmitted between horses, so make sure to treat your horses immediately if an infection is found.

Rain rot can really stress a horse out and make it hard for them to breathe when inflamed, so treatment needs to be immediate. Treatment is normally started with anti-fungal medication that will need several days (and sometimes longer) to be effective.

After the medication is in your horse’s blood stream, your horse will be moved to its regular pasture. It is important to treat your horse immediately to prevent the infection spreading to other horses.