Pastern Dermatitis / Scratches / Mud Fever

Pastern dermatitis, commonly known as scratches, mud fever, greasy heel, or cracked heels, is a multifactorial skin condition affecting the pastern, heel, and lower limb regions of horses. This frustrating condition results from the breakdown of the skin's protective barrier in these areas, followed by invasion of various infectious organisms including bacteria, fungi, and occasionally parasites. The resulting inflammation, crusting, and skin damage can range from mild, superficial changes to severe, debilitating lesions that cause significant lameness and require prolonged treatment. Pastern dermatitis represents one of the most common and challenging skin conditions encountered in equine practice due to its tendency to recur and its often stubborn response to treatment.

Pastern dermatitis affects horses of all ages, breeds, and disciplines, though certain populations face increased risk due to environmental exposure and anatomical factors. The condition occurs worldwide wherever horses are kept, with higher prevalence in regions with wet climates, heavy rainfall, or prolonged periods of muddy conditions. Horses living in poorly drained paddocks, those exposed to frequent washing or wet conditions, and those with heavy feathering around the pasterns are particularly susceptible. The condition may occur year-round but often increases during seasons with high moisture, whether from rain, snow, or dewy grass.

The impact of pastern dermatitis on equine health and welfare can be substantial, ranging from minor cosmetic and management concerns to severe pain and lameness. Mild cases may present as dry, flaky skin with minor crusting, causing minimal discomfort. Severe cases develop extensive, painful lesions with marked swelling, deep cracks, and granulation tissue that can render horses significantly lame and unable to work. The chronic, recurrent nature of the condition in susceptible individuals creates ongoing management challenges and can significantly impact the horse's quality of life and usefulness. Secondary complications including cellulitis and systemic infection can develop from severely affected limbs.

While pastern dermatitis can be challenging to treat, particularly in chronic or severe cases, most horses can be successfully managed with appropriate therapy addressing the infectious agents, environmental factors, and underlying predispositions. Early intervention before severe skin damage occurs improves treatment success and reduces the likelihood of long-term complications. Understanding the multiple factors that contribute to pastern dermatitis development is essential for effective treatment and prevention, as addressing only one aspect of this multifactorial condition often results in treatment failure and recurrence.

The primary causes of pastern dermatitis involve multiple infectious agents that take advantage of compromised skin barriers in the lower limb region. Bacteria, particularly Staphylococcus and Streptococcus species, are commonly involved in establishing infection once the skin is damaged. Dermatophilus congolensis, the same organism that causes rain rot, frequently contributes to pastern dermatitis, especially in moist conditions. Fungi including dermatophytes and yeasts may play primary or secondary roles. In some cases, particularly in horses with heavily feathered legs, the mite Chorioptes equi causes or contributes to the condition. Often, multiple organisms are present simultaneously, creating a complex polymicrobial infection.

While pastern dermatitis itself is not directly inherited, certain conformational and anatomical characteristics that increase susceptibility may have genetic components. Horses with white or non-pigmented skin on their lower legs appear more susceptible, as this skin may be more sensitive to environmental insults. Draft breeds and other horses with heavy feathering around the pasterns face increased risk because the long hair traps moisture and debris against the skin. Conformational factors that affect limb function or that create areas where moisture accumulates may predispose some horses. Individual variations in skin characteristics, immune response, and sensitivity to environmental irritants influence which horses develop the condition.

Environmental and management factors play crucial roles in initiating and perpetuating pastern dermatitis. Prolonged exposure to wet or muddy conditions is the most significant environmental risk factor, as moisture softens the skin, increases permeability, and creates conditions favoring bacterial and fungal growth. Standing in wet bedding, muddy paddocks, or dewy grass can all contribute. Irritation from sand, grit, or abrasive footing damages the skin barrier. Excessive washing of the legs, particularly if not thoroughly dried, paradoxically increases risk by repeatedly wetting the skin. Poor leg hygiene with accumulation of manure and debris also promotes skin breakdown.

Specific risk factors that increase the likelihood of developing pastern dermatitis include several management and horse-related considerations. Horses in heavy work that are frequently washed may develop the condition from repeated moisture exposure. Those living in poorly drained facilities face ongoing exposure to wet conditions. Horses with compromised immune function or concurrent illness may be less able to resist infectious organisms. Prior skin damage from wounds, chemical irritation, or previous episodes of pastern dermatitis creates areas of vulnerability. Nutritional deficiencies affecting skin health and immune function may contribute to susceptibility.

The pathophysiology of pastern dermatitis begins with compromise of the skin's natural protective barriers. The epidermis in the pastern region is subject to significant mechanical stress and environmental exposure. When moisture, abrasion, or other factors damage the protective layers, opportunistic organisms gain entry and establish infection. The inflammatory response to infection produces the clinical signs of redness, swelling, crusting, and exudation. Chronic or severe inflammation can lead to thickening of the skin, development of granulation tissue, and fibrosis that makes the area more susceptible to future episodes. The warm, moist environment created by exudation and crusting perpetuates the infection cycle.

Early warning signs of pastern dermatitis are often subtle and may go unnoticed, particularly in horses with feathered legs where the pastern region is not easily visible. The first indications may include mild pinkness or redness of the skin in the heel bulb and pastern area, visible only upon close inspection or during grooming. The skin may feel slightly warm compared to unaffected areas. Fine scaling or dry, flaky skin may develop, and the horse may show subtle sensitivity when the area is touched during grooming. A slight change in the texture or condition of the hair around the pasterns may be noted. Early detection at this stage offers the best opportunity for successful treatment before more severe changes develop.

The common symptoms of established pastern dermatitis become more obvious as the condition progresses. Crusting and scab formation develop over the affected skin, often appearing as thick, adherent crusts that may be difficult to remove. The skin becomes thickened and may develop horizontal cracks, particularly in the heel bulbs, giving rise to the term cracked heels. Exudate ranging from serous fluid to purulent discharge may seep from beneath the crusts. The hair in the affected area may become matted with exudate and crusts, or may begin to fall out, leaving areas of partial to complete alopecia. Swelling of the pastern and fetlock region develops as inflammation progresses.

Behavioral changes associated with pastern dermatitis reflect the discomfort and pain caused by the inflamed, cracked skin. Horses become sensitive to having their legs handled and may resist grooming, bandaging, or examination of the affected areas. Reluctance to walk through wet areas, puddles, or mud may develop. Some horses become difficult to pick up feet for hoof care due to discomfort when the fetlock is flexed. Stamping or shifting weight between limbs may indicate irritation or pain. In severe cases, obvious lameness develops, ranging from mild stiffness to marked lameness with reluctance to bear weight.

Physical signs of pastern dermatitis extend beyond the primary skin lesions as the condition progresses. Significant swelling of the affected limb may develop, sometimes extending from the coronary band to the cannon bone region. The skin becomes increasingly thickened and indurated. Deep, painful fissures may form in severely affected areas, sometimes bleeding or producing seropurulent discharge. Granulation tissue may develop in chronic cases, creating proud flesh that protrudes from cracks and eroded areas. Secondary bacterial cellulitis may develop, with marked warmth, swelling, and pain extending beyond the primary skin lesions. Lymphangitis with streaking lymphatic inflammation may be visible in severe cases.

Symptom progression in untreated or inadequately treated cases follows a pattern of deepening and expansion of skin damage. Early scaling and crusting progress to thickening and cracking of the skin. Cracks deepen and become painful, often bleeding when the horse moves. The affected area expands, potentially involving the entire pastern circumference and extending up toward the fetlock or down toward the coronary band. Swelling becomes more pronounced as inflammation and infection worsen. Lameness increases as the horse finds it increasingly painful to flex and extend the affected limb. Without intervention, severe cases can become debilitating.

Emergency symptoms requiring immediate veterinary attention include signs of systemic illness accompanying the skin lesions such as fever, depression, or loss of appetite. Severe lameness, particularly non-weight-bearing lameness, indicates significant pain and potentially serious complications. Rapidly spreading swelling and heat extending up the limb suggests cellulitis or lymphangitis that requires aggressive treatment. Signs of tissue necrosis, including dark discoloration or foul odor, indicate serious tissue damage. Any horse that becomes systemically ill in association with pastern dermatitis should receive immediate veterinary evaluation, as secondary septicemia can occur in severe cases.

Physical examination is the cornerstone of pastern dermatitis diagnosis and provides important information about severity, extent, and likely contributing factors. The veterinarian will thoroughly examine the affected areas after clipping any feathering that obscures visualization. Assessment includes evaluation of the type and extent of crusting, the depth and character of any cracks or ulcers, the degree of swelling and inflammation, and the presence of granulation tissue or other chronic changes. Examination of all four limbs is important, as multiple limbs are often affected. The overall examination assesses for signs of systemic illness, lymph node enlargement, and complications including cellulitis or lymphangitis.

Diagnostic testing helps identify the specific organisms involved and guides treatment selection, particularly for cases failing initial therapy. Cytology of impression smears from beneath crusts or from exudate can identify bacterial cocci or rods, fungal elements, and inflammatory cells. Bacterial culture and sensitivity testing identifies the specific bacteria involved and determines which antibiotics will be most effective. Fungal culture may be indicated if dermatophyte involvement is suspected. Skin scrapings examined microscopically can identify Chorioptic mites, which may be the primary cause or contributing factor in some cases. Skin biopsy may be recommended for chronic, refractory cases to rule out underlying conditions such as vasculitis, pemphigus, or neoplasia.

Advanced diagnostic procedures are occasionally needed for complicated or atypical presentations. Complete blood count and serum chemistry panels may be performed to assess for systemic involvement and underlying conditions. Radiography may be indicated if bone involvement is suspected beneath severe or chronic lesions. Ultrasonography can assess the extent of soft tissue involvement in cases with significant swelling. Biopsy with histopathological examination provides detailed information about the nature of the skin changes and can identify unusual underlying causes. For horses with recurrent or refractory pastern dermatitis, investigation for underlying conditions including liver disease, vasculitis, or photosensitivity may be warranted.

Differential diagnosis is important because several other conditions can cause lesions similar to pastern dermatitis. Primary chorioptic mange presents similarly but is caused by mites and may cause more intense pruritus. Photosensitization affects non-pigmented skin on the lower limbs but is associated with liver disease or specific plant ingestion. Contact dermatitis from irritant substances can cause similar lesions in contact areas. Coronary band abnormalities including coronitis or grease heel can extend into the pastern region. Vasculitis causes pastern swelling and may include skin lesions. Cellulitis and lymphangitis cause severe limb swelling that may mimic or accompany pastern dermatitis. Accurate diagnosis allows appropriate treatment targeting the specific causes in each case.

Initial treatment of pastern dermatitis focuses on cleaning the affected area and removing crusts to allow assessment and penetration of topical medications. The leg should be soaked in warm water or antiseptic solution to soften crusts, typically for fifteen to twenty minutes. Gentle removal of softened crusts using gloved fingers or soft cloths allows examination of the underlying skin and removes debris harboring infectious organisms. Any feathering should be clipped carefully to facilitate treatment and drying. The area should be thoroughly dried after cleaning, as residual moisture perpetuates the condition. This cleaning process may need to be repeated over several days to completely remove accumulated crusts from severe cases.

Medical management includes both topical and, in more severe cases, systemic antimicrobial therapy. Topical treatments following cleaning may include antimicrobial ointments or creams such as silver sulfadiazine, mupirocin, or preparations containing multiple antimicrobial agents. Drying agents such as zinc oxide-based preparations help absorb moisture and protect the skin. For cases with significant bacterial involvement, systemic antibiotics may be prescribed, typically trimethoprim-sulfamethoxazole or other broad-spectrum agents, with treatment courses often lasting two to four weeks. If mites are identified or suspected, treatment with ivermectin or moxidectin addresses the parasitic component. Antifungal therapy may be added if fungal involvement is documented.

Surgical intervention is occasionally required for complications of pastern dermatitis. Debridement of necrotic tissue may be necessary in severe cases with tissue death. Removal of excessive granulation tissue allows proper healing and reduces chronic inflammation. Drainage of abscesses that develop secondary to deep skin infection may be required. These procedures are typically performed under standing sedation with local anesthesia, though severe cases may require general anesthesia for complete treatment. Wound care following surgical debridement becomes an important component of ongoing management.

Supportive care is essential for successful pastern dermatitis treatment and often makes the difference between success and failure. The most critical supportive measure is keeping the affected area clean and dry. Horses should be housed in clean, dry stalls with absorbent bedding during treatment. Standing bandages may protect healing tissues and keep the area clean, though bandages must be changed frequently to prevent moisture accumulation. Turnout should be restricted to dry areas, avoiding mud, wet grass, and standing water. Fly control reduces irritation and contamination of healing lesions. Nutritional support, including possibly omega-3 fatty acid supplementation, promotes skin health and healing.

Rehabilitation and return to normal turnout must be approached carefully to prevent recurrence. Treatment should continue until the skin has fully healed and developed normal barrier function. Gradual reintroduction to turnout begins with short periods in dry conditions, with the legs inspected and cleaned afterward. Protective barrier creams or ointments applied before turnout can help protect vulnerable skin during the transition. Monitoring continues throughout the reintroduction period, with prompt treatment of any recurring signs. For horses with chronic susceptibility, ongoing preventive measures become a permanent part of management.

Treatment decisions must consider the severity of lesions, the horse's environment and ability to be kept dry, owner compliance capacity, and economic factors. Mild cases may be managed by owners with veterinary guidance using topical therapy and environmental management. Moderate to severe cases require more intensive veterinary involvement, including possible systemic therapy and close monitoring. Very severe cases with complications such as cellulitis may require hospitalization for intensive treatment. The prognosis varies considerably depending on severity, with mild cases usually resolving completely and severe chronic cases sometimes being very difficult to fully resolve.

Recovery timeline for pastern dermatitis varies substantially depending on severity and chronicity of the condition. Mild cases treated promptly typically show significant improvement within one to two weeks, with complete resolution within three to four weeks. Moderate cases require four to eight weeks of consistent treatment before the skin returns to normal. Severe cases, particularly those with extensive tissue damage, granulation tissue, or deep infection, may require three to six months of treatment and may never fully return to completely normal skin. The presence of chronic skin changes such as scarring, fibrosis, or permanent hair loss affects the timeline and completeness of recovery.

Post-treatment care and monitoring are essential components of successful long-term management. Even after visible healing, the skin in previously affected areas remains vulnerable to recurrence for some time. Daily inspection of healing and healed areas allows early detection of any relapse. Continued attention to keeping the legs clean and dry prevents recurrence from moisture exposure. Maintenance application of protective barrier products before exposure to wet conditions may help protect vulnerable skin. Long-term monitoring should continue indefinitely for horses with history of pastern dermatitis, as the condition has a strong tendency to recur.

Prognosis factors for pastern dermatitis include several considerations affecting the likelihood of complete resolution and risk of recurrence. Horses in which the condition is caught early, before extensive skin damage occurs, have better outcomes than those with advanced disease. The ability to control environmental factors, particularly moisture exposure, significantly influences success. Individual susceptibility related to skin type, pigmentation, and anatomy affects recurrence risk. The specific organisms involved and response to antimicrobial therapy influence treatment duration and success. Underlying conditions that may contribute to susceptibility, if identified and addressed, improve long-term prognosis.

Long-term soundness and use outlook depends on the severity of the episode and the success of ongoing prevention efforts. Horses with mild to moderate pastern dermatitis that resolves completely typically return to full use without restrictions. Those with severe cases may have residual skin changes including scarring, chronic thickening, or areas prone to breakdown that require ongoing management. In some cases, permanent changes limit the horse's ability to tolerate wet conditions or may require modified management indefinitely. With appropriate prevention strategies, most affected horses can maintain good quality of life and continue their intended use, though ongoing attention to lower limb care becomes a permanent part of management.

Management practices that minimize moisture exposure and maintain skin health form the foundation of pastern dermatitis prevention. Horses should have access to dry standing areas, either through well-drained paddocks or shelter during wet weather. Mud management in high-traffic areas using gravel, geotextile fabrics, or other drainage solutions reduces exposure. Stalls should be kept clean and dry with adequate bedding to absorb moisture. Avoiding prolonged standing in wet grass, particularly early morning dew, helps protect susceptible horses. When legs do become wet, thorough drying before returning the horse to its living area reduces moisture contact time.

Nutritional prevention supports skin health and barrier function through balanced dietary intake. Adequate protein intake supports normal skin structure and repair. Essential fatty acid supplementation, particularly omega-3 fatty acids from flaxseed or fish oil, promotes skin barrier integrity and may reduce inflammatory responses. Zinc plays an important role in skin health, and ensuring adequate dietary zinc supports normal skin function. Biotin supplementation, while primarily associated with hoof health, also benefits skin integrity. Overall nutritional balance that avoids deficiencies provides the foundation for healthy, resilient skin.

Exercise and conditioning practices can influence pastern dermatitis risk through effects on leg hygiene and moisture exposure. Thorough drying of legs after exercise, particularly after work in wet or muddy conditions, prevents moisture from remaining in contact with the skin. Avoiding excessive washing of legs helps maintain natural skin oils and barrier function. When washing is necessary, thorough drying afterward is essential. Using boots and wraps that allow moisture escape during work helps prevent moisture accumulation. Cleaning legs after turnout in muddy conditions, followed by thorough drying, reduces infection risk.

Environmental factors in the horse's living situation significantly influence pastern dermatitis risk and should be optimized for prevention. Paddock drainage should be assessed and improved where necessary to minimize standing water and mud. Gravel or footing improvements in gateways, water trough areas, and other high-traffic zones reduce mud exposure. Barn ventilation and stall drainage should prevent humidity buildup that can affect leg skin. For horses with heavy feathering, trimming excess hair around the pasterns improves air circulation and makes the area easier to keep clean and dry. Fly control reduces skin irritation that might predispose to secondary infection.

Preventive care measures for horses with known susceptibility should include regular inspection of the pastern region, application of barrier products before exposure to wet conditions, and prompt treatment of any early changes. Barrier products such as zinc oxide ointments, petroleum jelly, or commercial preparations designed for this purpose create a moisture-resistant layer that protects the skin. These should be applied to clean, dry skin before turnout in wet conditions. Regular hoof care maintains proper foot balance and reduces abnormal stresses on the pastern region. Education of all personnel caring for susceptible horses promotes consistent preventive practices.

Daily management adjustments for horses with or prone to pastern dermatitis center on maintaining clean, dry lower limbs and monitoring for early changes. Morning and evening checks should include visual inspection of the pastern and heel areas, ideally after removing any boots or bandages that might obscure the view. Any accumulation of mud, manure, or debris should be gently cleaned away and the area dried. Grooming should include attention to the pastern region, using appropriate brushes or cloths to remove dried material without causing skin damage. Horses in active treatment require medication application as prescribed, typically after cleaning and drying the affected areas.

Housing and turnout considerations for horses managing pastern dermatitis should prioritize dry conditions. During active treatment, horses should be housed in clean, dry stalls with absorbent bedding that is changed or topped up as needed to maintain dryness. If turnout is permitted, it should be limited to well-drained areas and avoided during wet weather or when paddocks are muddy. Dry lot turnout may be preferable to grassy paddocks where morning dew can wet the legs. For horses with chronic susceptibility, permanent modifications to their living arrangements, such as always having access to dry standing areas, help prevent recurrence.

Exercise modifications during active pastern dermatitis depend on the severity of lesions and degree of lameness. Horses with mild involvement may continue light work, with attention to keeping legs dry and applying protective products. Moderate cases may require rest from ridden work, particularly if boots or bandages are needed over affected areas. Severe cases with significant lameness should be rested until the condition improves enough for comfortable movement. When returning to exercise, starting gradually and monitoring for any worsening allows safe progression. Avoiding work in wet, muddy, or dusty conditions protects healing skin.

Monitoring and ongoing care for horses with pastern dermatitis history should include systematic tracking of leg condition and any recurrences. Keeping a log of flare-ups, including timing, severity, weather conditions, and management factors, helps identify patterns and triggers. Regular photographs of the pastern areas provide objective documentation for comparison over time. Awareness of weather forecasts allows proactive management adjustments before wet periods. Building habits of regular leg inspection into daily care routines ensures early detection of any recurring problems.

Quality of life and use considerations for horses with pastern dermatitis vary depending on severity and response to management. Most horses with mild to moderate involvement that responds to treatment can continue normal activities with appropriate preventive measures. Horses with severe or chronic involvement may require significant modifications to their management and possibly their use. Some horses cannot tolerate wet conditions without recurring problems, limiting turnout options. Draft breeds and others with heavy feathering may require permanent trimming to manage the condition. With consistent attention to prevention, most affected horses can maintain good quality of life, though ongoing management effort remains necessary.

Certain breeds face increased risk of pastern dermatitis due to anatomical characteristics and skin types. Draft breeds including Clydesdales, Shires, Percherons, and Belgians are particularly susceptible due to their heavy leg feathering, which traps moisture and debris against the skin. Other breeds with significant feathering such as Friesians, Gypsy Vanners, and Fell Ponies share this increased risk. The feathering creates a warm, moist environment perfect for bacterial and fungal growth while making the skin difficult to inspect and treat. Horses with white or non-pigmented skin on their lower legs, regardless of breed, appear more susceptible than those with dark-pigmented pasterns, possibly due to differences in skin sensitivity and susceptibility to environmental damage.

Use and discipline considerations influence pastern dermatitis risk based on exposure patterns and management factors. Horses in disciplines involving frequent leg washing, such as showing, face repeated moisture exposure that can predispose to the condition. Event horses and hunters working in varied terrain and weather conditions encounter more environmental challenges. Driving horses wearing boots or wraps for extended periods may develop moisture accumulation issues. Horses kept primarily outdoors in wet climates face higher environmental exposure than those stabled. Breeding farms with horses at pasture may see increased incidence during wet seasons. Understanding the risk factors associated with specific uses allows targeted prevention strategies.

Genetic testing for pastern dermatitis susceptibility is not available, but breeding recommendations should consider the known risk factors. When breeding horses with history of severe or recurrent pastern dermatitis, owners should be aware that offspring may inherit similar skin characteristics or anatomy that increases susceptibility. Draft and feathered breed breeders might consider selecting for individuals with cleaner legs and less problematic feathering. Maintaining records of pastern dermatitis history in breeding stock and their offspring helps identify potential hereditary patterns. Regardless of genetics, environmental management remains the primary factor in whether susceptible individuals develop clinical disease.

Several conditions commonly co-occur with or are related to pastern dermatitis in horses. Chorioptic mange, caused by the mite Chorioptes equi, produces similar lesions on the lower limbs and may be the primary cause or a contributing factor in some pastern dermatitis cases. Rain rot or dermatophilosis may occur simultaneously on other parts of the body and may involve the pasterns, particularly in horses with heavy moisture exposure. Cellulitis, a deeper bacterial infection of the skin and subcutaneous tissue, can develop as a complication of severe pastern dermatitis. Lymphangitis may follow or accompany severe cases, with inflammation of lymphatic vessels causing dramatic limb swelling.

Conditions with similar symptoms that must be differentiated from pastern dermatitis include several skin diseases and syndromes. Photosensitization causes similar lesions on non-pigmented skin but is associated with liver disease or ingestion of photodynamic plants. Contact dermatitis from irritant substances produces skin changes in contact areas but has a different cause and course. Vasculitis can cause pastern swelling and skin lesions but has characteristic histopathological features and different underlying causes. Pemphigus foliaceus may involve the pasterns along with other body areas and requires biopsy for diagnosis. Coronary band diseases including coronitis may extend into the pastern region and need to be distinguished from primary pastern dermatitis.

Potential complications of pastern dermatitis extend beyond the primary skin condition and can significantly impact the horse's health. Secondary bacterial cellulitis represents the most common serious complication, with infection spreading from the skin into deeper tissues, causing severe swelling, heat, pain, and systemic illness. Lymphangitis may develop when infection spreads through lymphatic channels, creating streaking inflammation up the limb. Scarring and chronic skin changes can result from severe or repeated episodes, creating areas permanently susceptible to breakdown. In severe chronic cases, fibrosis and thickening of tissues can lead to permanent limb enlargement. Lameness from pain or structural changes can become permanent in the most severe cases.