Things You Will Need:
Iodine shampoo
Clean curry comb
Clippers
Spray bottle
Vinegar (use only 1/3 of the size of the spray bottle and fill up with water)

Skin fungus, better known as rain rot, comes from damp conditions (weather or bathing) longer hair on a horse and sometimes a lack of grooming. Some cases are easier to treat than others. Rain rot shows up under the horse's hair. Skin fungus can become infected and need treatment from a veterinarian. Below are some simple steps to take before calling a vet.

1
Take a look at how bad the fungus is and if the clumps easily come off without taking skin, you have caught it at an early stage. When flesh is visible it is a more serious form of fungus.
2
Bathe your horse with iodine shampoo. Scrub the infected areas, trying to loosen up the clumps of fungus. Use the curry comb to scrub, but keep in mind that your horse will become sensitive as you work on their skin. Go slow and be careful to not cause too much pain.
3
Scrape any excess water off the horse and dry them off with a towel as good as possible. And spray the diluted apple cider vinegar over the infected area.

4
If you notice any areas that are really infected and the hair is especially long around these spots, use clippers to clip away the fur making it easier for you to work with the skin.

6
Treat the horse's fungus at least once a day and keep the horse as dry as possible. If you notice the fungus does not clear up and spreads, call your veterinarian for further assistance.