30 Horse Skin Diseases

There are hundreds of skin conditions and diseases in horses which can be caused by bacteria, virus, fungus, flies, ticks, mite, lice, environmental factors, and physical injuries.

A general examination, dermatological examination, and in some cases, a skin biopsy, is required for the definitive diagnosis of skin diseases so if you’re unsure ALWAYS consult a vet.

1. Bacterial Acne

Bacterial acne in horses is the result of infection with Streptococci aureus. The hair follicle becomes infected and develops small, very painful abscesses. This mostly occurs under saddlecloth and harness. The disease is confused with fly bites, feed allergies, ticks, or rain scalds. The infection is contagious, and you should be disinfected all clothes, harness, and grooming equipment that used in affected horses. Wash the affected area skin daily with povidone-iodine and chlorhexidine and maintain proper hygiene.

2. Bee Sting

Skin disease may be caused by stings from the hiney bee Apis mellifica. Bee stings can be seen still sticking out of the horse skin, usually surrounded by swollen patches. This can cause problems if the horse has been stung around the eyes, nose, throat, or mouth. Stings must be removed with care to avoid squeezing the venom sac. If it creates severe problems, you must consult with your vet to reduce pain and swelling.

3. Ulcerative Lymphangitis (Big Leg)

The ulcerative lymphangitis in the horse is caused by a number of bacteria. This infection is confined to the leg, which becomes swollen or enlarged from the pastern to the elbow or stifles, with numerous small points discharging pus. The limb is painful to touch. A big leg occurs when the infection spreads from a skin or hoof wound to lymph vessels draining the legs.

The wound must be cleaned, and antibiotic injections are given to achieve a complete cure. The type of antibiotic used will depend on what bacteria are causing the infection. The infection localized at the sites along these vessels, causing swelling of the limb with the formation of abscess and subsequent discharge.

4. Fly Bites

Enlarged fly bites are caused by the blood-sucking fly, Haematobia exigua. The buffalo fly has spread south from Queensland and the northern coast of New South Wales. It can cause irritation and sores on the ears, eyes, and abdomen. In a heavy infestation, severe malnutrition may occur. Insecticide can be sprayed onto the head and abdomen.

5. Coital Exanthema 

Coital exanthema in horses is the result of a virus (EHV-3), one of three types of the herpes virus that affects horses. This is a venereal disease that involves the penis of the stallion and vulval area of the mare. Affected animal transmits the virus to susceptible horses during mating. Some horses are a carrier and only show signs of disease if subjected to stress such as foaling and other illness.

Following infection, the seath of the penis or the lips of the vulva swell and redden. Watery blisters rupture, becoming ulcerated. Both mares and stallion should have sexual rest until the vesicles have healed. Mild antiseptic washes applied to the penis and genital area will help to heal. The disease may recur in the next breeding season in some horses, but it is rare.


6. Ear Mites 

Ear mites in horses caused by the mite Psoroptes cuniculi. A horse with ear mites will shake its head, be hard to handle around the head, and may have a discharge from the ear canal. These mites may also cause itchiness around the tail. Once ear mites are confirmed as the cause of the problem, the infection can be treated with ear drops that contain an insecticide.


7. Fibroma 

A fibroma is a tumor of the fibrous tissue just under the skin. It is a cutaneous tumor in horses that can occur anywhere in the body. It can appear as a simple swelling that is slow-growing, or as a cauliflower-like growth. If it grows rapidly, it can form ulcerative sores. The fibroma is often difficult to remove, particularly if treatment is delayed. They often involve the vital structure of the leg, such as nerves, blood vessels, and tendons. The only way of positively diagnosing the disease is to take a biopsy section for microscopic examination. Surgical removal is the usual treatment, but the drug cimetidine shows promises of being a useful treatment. Early diagnosis by your vet is important to achieve a satisfactory cure.

8. Fly Worry

Fly worry in the horses is caused by species of flies including the house fly, Musca domestica and the bush fly, M vetustissima. Flies settle on the moist area of the body, such as the corners of the eyes, the vulva, and the top of the penis. A large number of them can causes irritation and ulceration in the area. This can be a serious problem, especially around the eyes, as it can lead to conjunctivitis. Insecticidal and fly repellent creams or sprays can be used around the affected area. Use a fly veil to protect the eyes. If the horse has conjunctivitis, consult with your vet.


9. Leg Mange ( Chorioptic Menge)

The leg mange caused by the mite, Chorioptes bovis. Leg mange affects the lower limbs of the draught-type horses, but in heavy infestation can extend to the upper limbs, armpits, and groin. The mites cause extensive irritation as they cause bites and feed. The skin becomes moist with a bloody exudate. Affected horses repeatedly stamp their feet when being examined. Leg mange can be mostly confused with “greasy heel.” The application of insecticides is the only treatment.


10. Lice 

Lice infestation is caused by bitting or sucking lice. Horses with poor conditions and with long winter coats that are not groomed are more prone to heavy infestation. Biting lice live on the scarf and are usually found of the body and head. Sucking lice tend to under the mane, tail, and fetlocks, although they can occur anywhere in the body. Horses with a heavy infestation of biting lice become anaemic.

Horses can be treated with sprays or powder insecticides such as malathion. Rags and harnesses should be sprayed and left unused for 14 days, and a second treatment 17 days after the first treatment is necessary.

11. Equine Melanoma 

Melanomas are the tumors formed from the cells which produce pigment in the skin. They frequently appear around the anus or on the tail as hard lumps of varying sizes. Equine melanoma is found anywhere in the body. The tumors are slow-growing and usually non-invasive. In some cases, they may be malignant and spread other organs of the body.


Small melanoma can be removed surgically or frozen. This may be complicated by their association with vital structures like the muscular ring of the anus. The invasion of multiple large melanomas is difficult to remove. 


12. Mosquito Bites

Severe plaques of the mosquitoes can occasionally occur after spring and summer rains. Bitten may have much small skin swelling of the body areas not protected by rugs. Rugs and hoods will provide some relief. Residual insecticides can be sprayed on the horse. The swelling normally disappears in 2 to 3 days.

13. Heat Lumps

Heat lumps are a condition in which small painful lumps of up to 1 cm diameter develop in the saddle area. They often appear in the spring and summer and are thought to be an allergic response to insects bites or feedstuffs. They are often made worse pressure by the from the saddle when the horse is ridden. Some times lumps skin shrink without treatment, and others do not respond to treatment at all. Relieving pressure from the saddle is important, and the use of oral, topical, or injectable corticosteroids is favored by many vets.


14. Onchocercal Dermatitis

Onchocercal Dermatitis in Horse is caused by the larvae of the Onchocerceal parasite. This is dermatitis affecting the skin of the underside of the body and, occasionally, the chest, withers, neck, and head. Horses become itchy, and their hair thins. The skin is scally and develops lumps, and eventually, it brings to weep due to secondary bacterial infection. This condition can be treated with Ivermectin.

15. Photosensitization (Sun Burn) 

Photosensitization is caused by sensitization of unpigmented skin to sunlight following feeding on lush clover or medic pastures, or St John’s Wort. Chronic liver disease can also lead to photosensitization in horses. White skin areas are mostly affected, particularly on the nose, back, or legs. The affected skin is swollen and exudates serum, later cracking to leave raw bleeding areas. These areas are often covered by scabs and can be confused with rain scald. The treatment is done by keeping the horse in stable and use corticosteroid cream in affected areas.

16. Sweet Itch 

Sweet itch or also known as Queensland itch is very common in northern Australia and caused by the bite of the sandfly Culicoides basitarsus. When the sandfly bites the skin of a horse, a small lump is developed. Because the lumps are intensely itchy, the horse rubs itself, causing loss of hair. Serum oozes from the skin and scalds forms, gradually become thick and corrugated.

Treatment is aimed to relieve the pain and irritation by giving anti-inflammatory cream on the skin. Use fly repellent, keep the paddock dry and clean. Insecticides may be used in the breeding place of the sandfly.

17. Rain Scald/Mud Fever 

Rain scald is a skin infection caused by a bacteria Dermatophilus congolensis, and it is also called mud fever or greasy heel. The disease is characterized by a matting of hair with the formation of a scab under the hair mat, commonly along the midline of the neck and back, the face, muzzle, legs, and on either side of the rib cage.

Mud fever occurs behind the pastern when horses are standing or walking in wet grass or mud. In most cases, the disease is self-limiting and regrets after 3-4 weeks. Horses that have recurrent bout rain scald should be kept out of the rain and damp conditions.

18. Ringworm

Ringworm in horses is caused by the fungi Trichophyton or Microsporum, which is a common condition of the horses. The condition causes loss of hair on the skin and appears a ring-like appearance on the body. It is a contagious disease also a zoonotic disease.

19. Saddle Sore or Girth Galls

The girth galls or saddle galls in horses are caused by a poorly fitting harness and over-work with an ill-kept harness. Mild cases have a moist, painful area of the skin. Severe cases develop a deep raw ulcer, which is very painful. Spelling is essential until the saddle sore heals. Early cases may respond to the application of hot and cold packs, followed by the application of a drying agent. The attention of saddlery is necessary to prevent recurrences.

20. Sarcoids

Equine sarcoid is caused by papillomavirus that causes tumors, and certain horses are predisposed to the development of sarcoids. Sarcoids are the most common tumors of horses, which invade the surrounding tissues. They can look like other skin tumors like warts and healed wounds. The signs, diagnosis, and treatment with the control you will get in my article about Sarcoids.


21. Spider Bites 

Rare in the UK. Spider bites. Bitten horses have very painful swelling on the neck or body where they have been bitten. Crusted ice should be applied to the swollen area, followed by alcohol rubs.


22. Squamous Cell Carcinoma

Squamous Cell Carcinoma in Horse starts as a depressed ulcerating sore that gradually enlarges until it becomes raised above the skin surface with a red, raw surface. It can be found on any part of the body, but it is usually on the face, penis, prepuce, vulva, or eyes. Precancerous changes can sometimes be seen as white, slightly raised patches, especially on the eye, nose, and penis.


23. Stable Fly Bites

Stomoxys calcitrans is responsible for stable fly bites in horses. These bites can cause intense irritation in some horses. The bites appear as small raised lumps with a certain scab. The stable fly is most prevalent in summer and autumn. To keep fly numbers under control, you should dispose of manure and rotting vegetation and spray the sunny side of the stable walls with a registered insecticide.

24. Summer Sore (Habronamiasis)

Summer sores caused by the larvae of the worm Habronema can appear anywhere in the body where flies are able to rest and feed; around the eye, ear, prepuce, penis, or on any wound. Flies carry the larvae of Habronema on to these areas, where they cause severe inflammatory reactions. The use of Ivermectin is the best use of treatment.

25. Granuloma or Kunkers

Equine Swamp cancer or Kanker caused by several types of fungi and occurs on the legs and abdomen but occasionally seen on the other parts of the body like head. The affected area of the skin develops a tumor-like appearance. The horses often bite and kick at the growths. Joints, tendons, nerves, and blood vessels can be intimately involved with the tumor, making treatment difficult. Surgically removal of the tumor is only the treatment of granuloma.

26. Tail Itch 

Tail itch in horses is caused by Oxyuris equi, found in the large intestine of the horse. The adult worm is passed through the anus and lays eggs on the skin around the tail and anus. AS this causes irritation, the horse rubs its tail on the fences, trees, or stables. Hair may fall out of the tail. Scraping of the skin around the tail and anus may show the eggs. Broad-spectrum anthelmintics is the only treatment.

27. Urticaria 

Urticaria in horses is caused by insect bites, feed allergies, injection reactions, and contact irritants that are often incriminated. This is characterized by rapid development and the rapid disappearance of elevated round flat-topped plaques on the skin surface, swelling of the nostrils, eyelids, ear, and between the legs. Urticaria often regresses without treatment but in severe cases, requires veterinary consultation.

28. Warts/ Papillomatosis 

Warts are more common in young horses caused by a papillomavirus. They are greyish white cauliflower-like growths with short stalks attaching them to the skin. They vary from an mm to several cms in diameter. They are found in the muzzle, lips, faces, eyelids, and legs. Usually, they are harmless, although sometimes they grow very large and can interfere with the eyelids or the lips. The wart virus spread via direct contact between infected and susceptible animals.

29. Glanders

Glanders is one of the most ancient of all diseases recognized. A scourge of solipeds, glanders was frequently seen in an acute form in the ass, in a sub-acute form in the mule, and in the chronic form in the horse. The causal organism, Pseudomonas mallei, survives so poorly outsides those hosts, the disease was always most prevalent in horses massed for military or sports purpose. P mallei can produce glanders in a wide range of species, including humans and carnivores.

30. Tick Infestation 

The cattle tick, bush tick, and paralytic tick can all infect horses. This is often a severe local reaction to the attached tick with swelling around the site. Paralysis ticks, once adult and engorged, can cause progressive paralysis and death, especially in foals. In foals or adults where paralysis is due to the paralysis ticks, antiserum can be used successfully to treat. Chemicals are sprayed to remove the ticks from the body and in the environment.

Equine skin diseases are a very painful and irritating problem of the horse owner. You may face any or more skin diseases throughout the year. Proper management of stable, horses, and pasture may reduce most of the incidence of horse skin diseases. The above information will help to know the basics of skin diseases of horses.


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