Horse Rain Rot

Information on the causes and symptoms of dermatophilus and rain rot (rain scald) in horses.

    rain rot in horses

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    1. What is Rain Rot?
    2. What Causes Rain Rot?
    3. Diagnosing Rain Rot
    4. Help for Rain Rot
    5. More Information on Rain Rot

    What is Rain Rot?

    Rain rot or rain scald is one of the most common skin diseases in horses. This condition can be present in any horse around the world, but is most common in areas with high humidity and hot temperatures combined with heavy, drawn out periods of rainfall.

    This provides the perfect conditions for the organism that causes Rain Rot to reproduce and flourish. Though it is not a life-threatening condition, Rain Scald on a horse can cause great discomfort.

    Symptoms and signs of Rain Rot

    Rain rot or dermatophilosis can appear as:

    • Large crust-like scabs
    • Matted tufts of hair
    • Dozens of tiny scabs (pink with pus when the scabs are removed)
    • Small lumps on the horses’ skin or hair (early stages)


    The above-mentioned symptoms usually appear on the horse’s back and rump, fetlock (dew poisoning), front of the cannon bone, tips of the horse’s ears and around the eyes and muzzle.

    What Causes Rain Rot?

    The organism Dermatophilus congolense is responsible for the condition called rain rot. This organism is not a fungus, but it behaves like both bacteria and fungi. This organism is carried on the horse’s skin, and with a weakened immune system, it may then develop into rain rot.

    Causes that may contribute to rain rot include:

    • Shared contaminated barns, saddle blankets, leg wraps and brushes.
    • Extreme moisture (Horses with thick coats tend to suffer).
    • Damaged skin (by a cut or scrape) allows the organism to enter.
    • Poor stable management, damp stalls with poor ventilation and.

    Diagnosing Rain Rot

    Diagnosis is usually made by observation – your vet will look out for large, crusty, circular areas or small, raised areas with small scabs (a mass of raised hair is usually a tell-tale sign as the scabs cause the hair to stand upright). To make a specific diagnosis, your vet may send away some of the exudate to be identified under a microscope or by staining it with New Methylene Blue, Diff-Quick, or a gram stain.

    Help for Rain Rot

    Dermatophilus congolensis thrives in areas with no air – so removing the hair from affected spots is key. Scab removal is also recommended, allowing the organism exposure to oxygen. Do this with care, as it may be sore for your horse.

    Try wetting the scab first, for easier removal, then cleanse the wound with an anti-bacterial shampoo, and pat dry. For severe cases, antibiotics such as penicillin, ampicillin, streptomycin or gentamycin may be used. Immune-boosting drugs may also be recommended for the horse’s immune system.

    Note: If your horse has a severe case of rain rot, discuss treatment with your veterinarian and discuss the antibiotics listed above and possible side-effects. Dangerous secondary bacterial infections known are staphylococcus (staph), and streptococcus (strep).

    More Information on Rain Rot

    Tips related to Rain Rot

    Here are some helpful tips to prevent the spreading of the organism:

    • Remove equipment that may rub and irritate your horse’s skin (saddles and leg wraps)
    • Disinfect everything you use on multiple horses. This includes anything you use on an infected horse such as halters, saddle pads and brushes. Favorite rubbing spots like a stall door or fence should also be disinfected.
    • During wet weather keep your horse under shelter, or use a rainproof and breathable blanket.
    • Keep your horse in a dry, clean area that is well ventilated.
    • Give your horse added protection against biting insects (if you use a net, be sure your horse cannot get stuck in it).
    • Isolate a horse with rain rot from any others.
    • Wash your hands thoroughly after working with an infected horse.


    To treat your horse (be sure to wear gloves):
    • Use a natural shampoo that lathers well. Let sit for 10 minutes, then rinse well. Be sure to dry gently, yet thoroughly – as the organism is likely to reoccur in moisture!
    • Remove all scabs that are present – be gentle – this may take a few sessions over a few days. The washing with shampoo will help to moisten them. Dry the horse immediately after scab removal (try a casual walk in a sunny area, where dry wind can help dry the wet areas).