Scratches in Horses: Causes, Symptoms & Treatments

Scratches, also known as pastern dermatitis, is an inflammatory skin conditions that affects the lower limbs of horses. It is characterized by irritation and sometimes infection of the skin, usually around the hind pastern or fetlock.

The condition is often caused by a combination of factors such as prolonged exposure to wet and muddy conditions, which can weaken the skin’s barrier and allow pathogens to penetrate.

If left untreated, scratches can lead to more severe infections, cellulitis, or lymphangitis. It can also cause significant discomfort and lameness in the horse.

While scratches can affect different breeds of horses, it is most common in draft breeds and those with feathers on their lower legs.

Both treatment and prevention of this condition depend on maintaining a clean and dry environment for the horse.

What is Scratches in Horses?

Scratches is a common name for Equine Pastern Dermatitis (EPD), which is not a single disease but rather a multifactorial syndrome. This means that it is a condition influenced by a variety of factors rather than a specific singular cause. ^[1][2]

Pastern dermatitis in horses varies in its severity, and the term “scratches” is often used to refer to a milder form of this condition. The names “mud fever” or “mud rash” are also commonly used, reflecting the condition’s frequent association with wet and muddy conditions.

Scratches typically affects the skin on the backs of the horse’s pasterns and sometimes the heel bulbs. The condition is most commonly seen in both hind limbs, but it can also occur in the front limbs or in only one limb. This condition predominantly affects the unpigmented (white) lower legs of horses. ^[2][3]

Horses with scratches develop redness, swelling, hair loss, dry scales, and crusting with potential thickening of the skin in the pastern region. Itchiness and pain are also common symptoms. ^[3]

In some cases, skin lesions can spread to the front of the pasterns and up onto the fetlock, worsening into a more serious form of EPD. Secondary bacterial infections may occur as well, making the condition more difficult to treat. ^[3]

Forms of Pastern Dermatitis

As noted above, scratches is a mild form of EPD, which refers to inflammation and irritation of the skin around the pastern region. If not managed properly, EPD can escalate into more severe forms including exudative dermatitis and chronic proliferative dermatitis.

Exudative EPD

Commonly known as “grease heel” or “dew poisoning”, this form of pastern dermatitis is characterized by exudation (discharge of fluid) in the affected skin areas. Educative EPD also involves skin reddening, erosion, hair loss, and crusting dermatitis.

Conditions such as epidermolysis, leading to sores and blisters, and vasculitis, involving inflammation of blood vessels, are often associated with this form​ of EPD. ^[3]

Chronic Proliferative EPD

Often referred to as “grapes” or “verrucous pododermatitis”, this form of EPD is characterized by the overgrowth of granulation tissue (proud flesh), which can harden over time.

It may also manifest as nodules of thick, rough or leathery skin. Particularly in draft breeds, the skin may develop cracks and wart-like growths​. ^[3] Chronic proliferative EPD is the most difficult form of pastern dermatitis treat. ^[3]

Causes

Scratches is caused by various factors that weaken or damage the skin’s natural protective barrier, leading to inflammation and irritation.

Contributing causes may include prolonged exposure to moisture, bacterial or fungal infections, skin trauma, and underlying health conditions that impair the horse’s immune response or circulatory health.

Predisposing factors that increase a horse’s risk of developing scratches include: ^[4][5][6]

• Damp or muddy conditions
• Poor hygiene or grooming
• Feathering on the legs
• Large pastern circumference
• Unpigmented legs (white markings up to pastern level)

While the full range of contributing factors is not entirely understood, several causes have been identified as playing a significant role in the onset of scratches: ^[4][5][7]

Environmental Factors

Prolonged exposure to wet conditions is a major contributing factor for scratches in horses. Excessive moisture can weaken the skin barrier, making it more susceptible to irritation and infection. A damp and muddy environment also increases exposure to pathogens, such as the Staphylococcus aureus bacteria.

High pasture stocking density, poor stable hygiene and manure management, along with ground surfaces with poor water absorption, can also contribute to scratches. ^[1][5]

Feathering on the horse’s legs, which can retain moisture, soil, and debris, is also linked to an increased risk of pastern dermatitis. ^[5]

Irritants and Allergens

Scratches may also be caused by contact dermatitis from allergens or physical and chemical irritants. Examples include: ^[1][5][6]

• Skin abrasion due to tack or training devices, such as bell boots
• Contact with urine, diarrhea, or other fluid secretions
• Reactions to chemicals in shampoos, lotions, topical medications and treated stall bedding
• Allergies to plants, insect bites, pollen or other environmental triggers
• Skin irritation caused by sandy ground and alkaline soils.

Bacterial and Fungal Infection

Bacterial and fungal infections also play a major role in the development of scratches in horses. When the skin is compromised due to moisture, trauma, or irritation, it is more vulnerable to pathogens.

The most common bacterial culprits in scratches are Dermatophilus congolensis, Staphylococcus spp., Streptococcus spp., and Fusobacterium necrophorum. ^[6]

Fungal infections linked to scratches include Dermatophytes and Malassezia spp. ^[6]

Mites or Other Parasites

A recent study showed that nearly 27% of horses with pastern dermatitis were affected by chorioptic mange. Also known as chorioptic acariasis, this a skin condition in horses caused by the Chorioptes spp. mite.

These microscopic ectoparasites burrow into the horse’s skin, causing irritation and itching. Horses with mange exhibit behavioral signs such as stamping, biting, chewing, rubbing, or scratching at the skin. This condition is especially prevalent in draft horses with feathered pasterns.

Scratches in horses may also be associated with other parasitic infections including:

• Trombicula spp. mites
• Strongyloides westeri.
• Pelodera spp.

Photosensitization

Photosensitization is a skin reaction in horses that occurs when certain substances in the body react to sunlight or UV radiation, leading to skin damage. This reaction can be a contributing factor to the development of scratches.

Photosensitization in horses typically occurs when a horse ingests plants containing photodynamic agents or when there is liver damage that prevents the normal breakdown of chlorophyll. The photodynamic agents are then circulated to the skin, where they react with sunlight, causing damage to the skin cells.

Examples of plants that contain photodynamic substances include:

• St. John’s wort
• Buckwheat
• Perennial rye grass
• Certain types of clover

Pastern leukocytoclastic vasculitis (PLV), also known as photo-aggravated vasculitis, is another suspected cause of scratches linked to sun exposure. This disease is not well understood but can affect mature horses, especially those with un-pigmented lower legs.

Scratches is also more prevalent in the summer, which may be attributed to increased sun exposure. ^[3]

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Signs & Symptoms

In the initial stages of scratches, typical indicators are inflammation and a reddening of the skin on the pasterns’ rear. ^[3] In horses with feathered legs, these early signs might go unnoticed at first.

Other common symptoms include: ^[1][4]

• Crusty skin
• Scaling
• Thickening of skin
• Edema (swelling)

Severe Signs

If scratches progresses into a more severe form of EPD symptoms may include: ^[4][5]

• Skin sores or lesions
• Oozing from skin lesions
• Hair loss
• Lameness
• Loss of appetite
• Parasitic infestation (myiasis)

In chronic or advanced cases, the skin may become rough, thick or leathery, and develop cracks or fissures.

Complications

If not treated promptly, complications from scratches may arise including:

• Secondary Infections: The broken skin and inflammation associated with scratches can make it easier for bacteria and fungi to invade, leading to secondary infections.
• Cellulitis: This is a potentially serious bacterial infection that affects the deeper layers of the skin and the underlying soft tissues. It can cause significant swelling, redness, and pain. In severe cases, cellulitis can lead to systemic illness.
• Exuberant Granulation Tissue (Proud Flesh): Horses can develop excessive granulation tissue during the healing process, which can impede proper wound healing. ^[4][5]
• Lymphangitis: In some cases, scratches can lead to lymphangitis, an inflammation of the lymphatic vessels. ^[4][5]

Chronic Progressive Lymphedema

Chronic Progressive Lymphedema (CPL) is a potential complication of scratches that is most prevalent in draft breeds such as Clydesdales, Belgians, Cobs, and Shires. ^[3][4]

CPL is characterized by progressive swelling in the lower legs, tissue scaring, and the formation of skin folds and nodules. Hoof abscesses are also common in horses with CPL. ^[3][8]

CPL is linked to lymphatic dysfunction and may involve immune system compromise and anomalies in elastin, a key component of connective tissue. ^[3] Secondary skin infections, such as those associated with scratches, can trigger the onset of lymphedema in susceptible horses. ^[8]

There is no treatment for CPL. As the disease progresses, enlargement of the lower extremities becomes irreversible, leading to reduced mobility over time. ^[3]

Management of horses with CPL focuses on slowing the disease’s progression and maintaining the horse’s quality of life. However, the progressive nature of CPL often leads to euthanasia in affected horses. ^[3][8]

Diagnosis

If you suspect your horse is affected by scratches, consult with your veterinarian for an accurate diagnose and treatment plan. Your veterinarian will examine your horse’s lower limbs and conduct testing to determine the underlying cause of skin irritation.

Your veterinarian will request a comprehensive history of your horse’s symptoms, including the timeline of when the issue first appeared. Since many owners initially try to manage scratches with home remedies or topical treatments, your veterinarian will likely inquire about any such attempts and their effects on the symptoms. ^[3]

Your veterinarian may also ask for information on your horse’s living conditions, such as bedding type, pasture environment, and exposure to moisture. ^[3]

The severity of lesions and the level of discomfort and itchiness (pruritus) from scratches can be assessed using a scoring system.

In horses with feathered legs, it’s necessary to trim the hair for an accurate evaluation of the lesions. If the process of clipping is too painful for the horse, sedation and preliminary cleaning to soften the crusts may be required before proceeding. ^[5]

Differential Diagnosis

Because scratches may involve other infections or conditions, various differential diagnoses may need to be considered. These include: ^[3][4][5]

• Pastern Leukocytoclastic Vasculitis
• Dermatophytosis (ringworm)
• Dermatophilosis
• Pastern folliculitis
• Pemphigus foliaceus
• Sarcoidosis
• Primary or secondary photosensitization

Depending on the horse’s breed and symptoms, CPL may be considered. ^[5] In sub-tropical and tropical regions, other conditions including phytosis and epizootic lymphangitis should be kept in mind.

Chorioptic mange should also be suspected if multiple horses from one farm are affected, particularly in draft horses with feathering. ^[3]

Diagnostic Techniques

Your veterinarian may diagnose scratches based on the horse’s history and symptoms alone. However, in severe or chronic cases not responsive to treatment, further diagnostic tests may be required to determine the underlying cause of the skin irritation.

Skin Scraping

Skin scaping is a procedure used to check for the presence of parasites, particularly mites. Multiple skin scrapings may be needed to rule out mites. ^[3][5]

The veterinarian gently scrapes the top layer of the skin from an affected area. The collected material is then examined under a microscope to identify any parasites.

Bacterial Culture

A culture test is performed to determine if there is a bacterial or fungal infection and to identify the specific type of microorganism causing the infection.

A sample of skin or discharge is collected from the affected area. This sample is then placed on a culture medium that encourages the growth of bacteria or fungi.

While bacterial culture remains the standard practice for investigating bacteria linked to scratches, it is not the most effective method for identifying all bacterial species. Recent research indicates that next-generation sequencing of bacteria offers a more thorough overview of pathogens involved. ^[5][9]

Skin Biopsy

Skin biopsy is used in challenging or persistent cases where the cause of the skin condition isn’t clear or the horse does not respond to standard treatments. It helps to rule out other serious skin diseases.

A small piece of skin tissue is removed from the affected area under local anesthesia. The tissue sample is sent to a pathology laboratory where it’s examined microscopically.

A pathologist looks for specific changes in the skin cells, the presence of infectious agents, and other signs that may indicate the underlying cause of the condition.

Treatment

Consult with your veterinarian to determine the appropriate course of treatment for scratches in your horse. ^[3][5] The treatment program will be tailored to address the specific factors contributing to the condition in each individual case.

Treatment typically involves keeping the affected area clean and dry, along with the application of topical medications. These may include antibacterial or antifungal agents to combat infection, as well as corticosteroids or anti-inflammatory drugs to reduce swelling and discomfort. In some instances, systemic treatments such as oral antibiotics may be necessary. ^[3][5]

For horses with feathered legs, it’s crucial to keep the feathers trimmed to ensure that topical treatments are applied directly to the skin and can act effectively. ^[4]

While topical treatments are generally safe, they can sometimes cause irritation, so it’s important to monitor the horse’s response and adjust the treatment as needed. ^[4]

With early identification and appropriate treatment, most cases of scratches can be resolved within a few weeks. ^[10]

Antifungal Treatments

Antifungal treatments will be used used in cases of scratches attributed to fungal infections. Topical antifungal medications include dips, sprays, and shampoos containing the following ingredients:

• Enilconazole
• Miconazole
• Ketoconazole
• Chlorhexidine

Systemic antifungal medications refer to drugs that work throughout the horse’s entire body rather than just at the site of infection. Examples of systemic antifungal drugs include:

• Ketoconazole
• Itraconazole
• Fluconazole
• Griseofulvin

Antibiotics

Antibiotics are used to treat bacterial infections linked to scratches. To prevent antibiotic resistance, their use should be targeted and specific, focusing on eliminating the bacteria associated with scratches in your horse.

The most frequently used antibiotics for treating scratches are trimethoprim-potentiated sulfonamides, commonly paired with topical antibacterial shampoos.

Some horses may have adverse reactions to these antibiotics, resulting in skin issues like welts, itching, severe inflammation, allergic reactions, anemia, and leukopenia (a decrease in white blood cells). In cases where a horse cannot tolerate sulfonamide drugs, injectable enrofloxacin may be used as an alternative.

Systemic antimicrobial and anti-inflammatory treatments may be used if signs of discomfort, pain, lameness, or fever are apparent.

Topical Antibacterials

Based on your veterinarian’s assessment, a variety of antibacterial products can be effective for treating scratches. Some commonly recommended antibacterial shampoos include:

• Benzoyl peroxide (2%)
• Ethyl lactate
• Chlorhexidine (2% and 4%)
• Miconazole shampoo (1%)

Topical antibacterial ointments that can be used include:

• Mupirocin (2%)
• Miconazole (2%) and cholorhexidine (2%)
• Ketoconazole (1%) and chlorhexidine (2.3%)
• Enilconazole
• Selenium sulfide (only effective against Malassezia spp.)

Antiparasitic Therapies

If a parasitic infestation is detected, the following antiparasitic medications may be used to treat scratches:

• Ivermectin (1%)
• Fipronil spray (0.25%)
• Selenium sulfide
• Lime sulfur concentrate
• Malathion (0.5%)
• Dexamethasone
• Prednisolone
• Pentoxifyline

To prevent anthelmintic resistance, closely follow your veterinarian’s guidelines for antiparasitic treatment.

Historically, topical organophosphates were used to address cases of scratches involving parasites. However, because of concerns related to environmental toxicities, other treatment options should be considered first.

If chorioptic mites are involved, environmental decontamination of the barn, stalls, bedding, tack, and grooming equipment is required to prevent reinfection. Furthermore, all animals that have been in contact with the affected horse should receive treatment as well.

Corticosteroids

Topical corticosteroids can be used to help control inflammation associated with immune-mediated conditions, such as pastern leukocytoclastic vasculitis or pemphigus. Medications may include:

• Triamcinolone spray (0.015%)
• Hydrocortisone (1%)
• Betamethasone (1%)
• Alclometasone dipropionate (0.05%)
• Trimethoprim-sulfamethoxazole
• Enrofloxacin

However, prolonged application of corticosteroids is not recommended as it may delay wound healing and inhibit skin growth.

Other Treatments

Several other topical remedies for scratches are available, comprising formulations with these specific ingredients: ^[5]

• Zinc oxide
• Dexpanthenol
• Colloidal silver
• Manuka honey
• Benzoyl peroxide
• Aluminum acetate
• Magnesium sulfate
• Silver sulfadiazine

While povidone iodine is commonly used, experts advise against its use because it may be irritating to the skin. ^[5]

Some practitioners also recommend placing padded, water-repellent bandages over topical medications applied to the pastern region. If using bandages, make sure to change the material every one to two days. ^[3]

Management and Prevention

Proper environmental management is key to preventing the recurrence of scratches in horses. Environmental modifications should focus on maintaining a clean, dry environment and minimizing exposure to pathogens.

Suggested management practices include: ^[3][5][6]

• Thoroughly cleaning and drying your horse’s legs after exposure to moisture or riding in sand.
• Implementing proper mud management techniques around your barn and in pastures to prevent excessive moisture accumulation.
• Ensuring proper drainage in all areas where horses are kept to prevent standing water.
• Avoiding overstocking pastures or paddocks to reduce mud and maintain better ground conditions.
• Keeping horses prone to scratches in a clean, dry stall during wet weather to limit their exposure to moisture.
• Avoiding turnout in pastures or paddocks before the morning dew has dried, thereby reducing the horses’ exposure to wet conditions.
• If a contact allergy to wood shavings is suspected, exploring alternative bedding materials to mitigate allergic reactions.
• Feeding a balanced, forage-based diet with adequate zinc and vitamin E to support overall skin health and immunity.
• If photosensitivity is suspected, avoiding UV light exposure by stabling during daylight or using leg wraps.
• If poor circulation or lymphatic flow are suspected factors, ensure the horse receives regular turnout and exercise.

Susceptible horses may also benefit from application of a barrier cream before exposure to moisture or other environmental irritants. ^[5] Consult with your veterinarian for personalized recommendations.

Grooming Practices

Maintaining good grooming practices plays a significant role in managing scratches. Regular grooming not only aids in early detection of skin irritations, but also promotes overall skin health.

If your horse has feathers, keep the hair over their pasterns clipped to decrease moisture retention. Monitor the skin under the feathering closely, especially during the wetter months of the year when pastern dermatitis more prevalent.

Prognosis

The prognosis for horses with scratches depends on the underlying cause and the presence of any coexisting conditions. In most cases, the prognosis is good, especially when the condition is identified and treated early.

Most horses with scratches respond well to treatment, with the skin returning to its normal state within a few weeks. ^[3][5]

Horses that develop conditions such as Pastern Leukocytoclastic Vasculitis (PLV), Chronic Progressive Lymphedema (CPL), or other complicating factors may require more extensive treatment to effectively resolve the skin irritation.

Summary

Scratches is a skin condition that causes inflammation, infection, and irritation to the lower limbs of horses. It is typically caused by long exposure to moisture, poor hygiene and unpigmented legs, amongst other health and environmental components.

Scratches presents as irritation to the skin such as redness, thickening of skin, swelling and potentially even hair loss, skin lesions or lameness. Your veterinarian should be consulted to determine an accurate diagnosis and treatment program.

Treatment primarily includes antibacterial or antifungal agents to combat infection, as well as corticosteroids or anti-inflammatory drugs to reduce swelling and discomfort.

To prevent and manage scratches, maintaining a dry environment for your horse is imperative. Additionally, providing a well-balanced diet will help support their immune system and reduce the risk of scratches.

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