Horse Skin Conditions

Claire Dunling

The likes of sweet itch, mud fever or ringworm can be troublesome for horse and owner alike. No one likes to see an animal suffer. Following close preventable measures can help keep the nasty horse skin conditions away from the yard.

Sweet Itch

in horses is a skin condition caused by an allergy to the saliva of certain biting flies. The severity of sweet itch depends on the degree of allergy or reaction to the insect bites. The allergy causes the horse to be itchy and rub the skin, in fact, they can actually rub the hair off the affected areas (upper neck, back, tail base and ventral abdomen).

This problem is usually encountered in the warmer months when insects are more active so reducing the amount of exposure is the best form of control to prevent the development of sweet itch in horses. therefore, stabling the animals at high-risk times, rugging the horse, using a fly and insect repellents can all help to reduce a horse’s exposure and the chances of developing sweet itch. Your vet will be able to offer advice on forms of reducing the exposure as well as appropriate treatment that are available to control the condition.

Mud fever in horses

Mud fever in horses is caused by the same organism as rain scald and is associated with damp muddy conditions. However, any damage to the skin surface can allow the bacteria to invade the skin and initiate the condition. Signs of mud fever in horses include matted, crusty scabs on the legs which tend to be around the coronet, heels and pastern. As usual, prevention is better than treatment and hence muddy areas of the paddock should be avoided.

If legs do get muddy this should be allowed to dry and then brushed off and any scabs should be observed for signs for problems. Your vet will be able to provide further advice on mud fever treatment.

Ringworm in horses

Ringworm in horses is not caused by a worm but it is actually due to infection of the skin by one or two types of fungi – Trichophyton or Microsporum. These fungi live in the environment (dirt, wooden fences etc.) and horses pick them up when in contact (rubbing themselves on a fence). Horses may also be infected with ringworm by other horses or animals (cattle) or infected tack or grooming utensils. Young horses are at greater risk from ringworm than older animals as immunity to the fungi develops with age.

Signs of ringworm are small 1-2cm circular tufted areas from which the hair will eventually fall out to reveal scaly skin. Ringworm generally occurs on areas of the body in contact with tack, clothing and riding boots. Treatment is aimed at both the horses and removing any possible sources of contamination.


Melanomas are tumours of the skin, which are derived from the pigment producing cells. They therefore have a heavily pigmented or darkened appearance. They are reasonably common and have a reported incidence of between 4% and 15%. They occur anywhere on the body but are more common in older horses with lighter coats. In fact, in old grey horses the incidence has been recorded as high as 80%.  These tumours are initially benign (unlikely to spread) but eventually the majority of them develop into malignant tumours and spread.

Squamous cell carcinomas

Squamous cell carcinomas are a type of skin tumour that is reportedly the second most common skin tumour of horses. They most frequently occur in horses between the age of 8 and 14 years but have been found in horses from 1 year old to 29! They are more common in lighter coloured horses as sunlight has been implicated as a cause of them. They can occur anywhere on the skin of a horse but are more commonly found on the hairless areas such as eyelids, lips, nose, vulva and prepuce. Early diagnosis is essential and your vet may even recommend removal of them to prevent further spread.

Horse sarcoids can appear in a number of different forms and can look similar to other skin tumours. It is essential that any lumps are discussed with your vet immediately.

Horse sarcoids

The most commonly diagnosed skin tumour found is horse sarcoids, which have been reported to account for nearly 90% of all skin tumours in horses. Luckily though they are non-malignant (unlikely to spread), however horse sarcoids can invade local tissue and cause irritation to the horse. Also, if they are knocked and bleed they will attract flies and increase the irritation. Horse sarcoids can appear in a number of different forms and can look similar to other skin tumours. It is essential that any lumps are discussed with your veterinary surgeon as soon as they are noticed.

Rain scald in horses

Rain scald in horses is a bacterial infection, which causes scabs to form on the back, rump and lower limbs. These scabs can be easily removed to reveal patches of moist raw skin. rain scald in horses is caused by prolonged wetting of the skin which allows the bacteria to invade. It is important that you contact your veterinary surgeon for advice on rain scald in horses as there are a few other conditions which can appear similar. Rain scald in horses can be avoided by ensuring the skin remains dry so stabling the horse or applying a weather proof rug can reduce the risk of rain scald developing.

This post is an opinion and should only be used as a guide. You should discuss any change to your horse’s care or lifestyle thoroughly with you vet before starting any program or treatment.

If in doubt contact your veterinary practice

And always keep your vet's phone number handy - just in case!