Scratches or Mud Fever

Disclaimer: The following is only general information. If you believe that your horse has a problem please call your veterinarian as soon as possible.

This condition has many names, depending on where you live, however Scratches, Dew Poisoning, Pastern Dermatitis, Mud Fever, Grease Heel or Greasy Heel are all a form of dermatitis that affects the skin around the pastern and fetlock. It is extremely uncomfortable for the horse and if it is allowed to develop can cause great pain and even lameness. Winter and Spring, when it is wet and cool, are the worst times for Scratches or Mud Fever.


greasyheelProbably the first signs you will see are crusty, crumbly, scabs between the fetlock and the heal of the back legs. The front legs can also develop these scabs however it is usually found on the back legs first. If the problem is allowed to progress the scabs or lesions can break open and bleed, the legs will become swollen and sore and the skin may thicken. In very serious cases the heel can crack open and bleed causing severe pain and loss of appetite. If left untreated the open sores can be difficult to heal and can result in ‘proud flesh’ and permanent hair loss.


This condition has four stages and the causes of each stage are different.


Stage 1: The horse’s skin softens because they are kept in muddy yards or they are walking through wet grass due to rain or heavy frosts. Some breeds, especially those with long hair or feathers around the lower leg, are even more susceptible.

592_chorioptesStage 2: The softened skin breaks open allowing ‘chorioptic’ mites or other agents to invade the cracks. Note. This type of mite has short legs and lives on top of the skin. They eat the skin flakes that are shed constantly by the horse. Their numbers increase dramatically in cool, wet conditions. These mites should not be confused with mites that burrow under the skin.

Stage 3: These openings in the skin now allow either Staphylococcus or Dermatophilus Congolensis bacteria to enter and cause infection. It is the bacteria that can cause the crumbly scabs and hair loss. Note. Staph bacteria live everywhere, on skin, inside noses and in the soil. Likewise D. congolensis lives within the skin of mammals. These bacteria only cause infection when they can get through the ‘skin barrier’ or the immune system is not working properly.

Stage 4: At this stage a fungal infection can enter the infected area. Once the fungus has entered it lives within the skin not just on the surface.


Because there are a number of factors that cause this condition the treatment has to address all of the causes – environment, bacterial infection, mites and fungal infection.

Remove the horse from muddy areas and long wet grass. If possible, place the horse in a dry, clean area. Note: If you are using a stable, use wood shavings or sawdust rather than straw. Straw can be abrasive and loaded with fungal spores that may cause further infection.

Clip away the hair on the affected area from the coronet to the fetlock and further if the condition has progressed up the leg

Wash the mud and dirt off the legs. This will also soften the scabs.

Gently pick the scabs off (these need to be removed so that you can treat the staph infection). Note: Be careful when removing the scabs as the skin will be tender. Wear your riding helment and ask for assistance.

Wash down the legs with an antibacterial/antifungal solution (these preparations should be diluted – the skin is already tender so follow the instructions from your vet)

Dry legs with disposable towels (paper or cloth)

You need to kill the mites that live on the skin so they should respond to a spay of something like a 25% solution of fipronil. Note: This is the active ingredient in Frontline, which is only approved for use on dogs and cats. It is commonly recommended by vets, however you should ask your vet for their recommendation and take their advice.

Allow to dry and apply an antibacterial, antifungal and anti-inflammatory ointment or cream. This will soothe the skin as well as treat the causes. Note: There are several excellent products, however they may be marketed under different brand names in different countries, so ask your vet for his or her recommendation. The antifungal will need to penetrate the skin to be effective.

If the lesions are severe you may need to cover the area with a gauze dressing and a snug (not tight) bandage. This should be changed every second day.

If you are leaving the area unbandaged then repeat treatment daily.

Continue treatment for about 2 weeks.

This treatment is a guide only and you should rely on your vet for treatment options and product recommendations.


Inspection of your horse should occur daily for stabled or yarded horses and every few days for pasture horses. Feel down their legs and pastern, back and front, for scabs and rough skin.

Try to keep your horse out of muddy areas.

Regularly clean off the mud and dry the legs with disposable towels.

Don’t wash too often with detergents as these may dry the skin and actually cause the skin to crack.

Remember you are dealing with bacteria, fungus and mites so good hygiene is important for your horse, your horse tack and yourself. Always wash your hands thoroughly after treating your horse and disinfect any cuts that you may have.


The above information is only general in nature. If you believe that your horse has a problem, please call your veterinarian as soon as possible.