What Causes Mud Fever in Horses? A Complete Guide
Share
If your horse has ever come in from the field with sore, scabby legs, you've probably found yourself asking: what actually causes mud fever in horses? It's one of the most common skin conditions during the wetter months, and understanding the root causes is the first step toward keeping your horse comfortable. Mud fever, also known as pastern dermatitis or "cracked heels", develops when the skin on the lower legs becomes weakened, allowing bacteria and fungi to take hold.
In this guide, we'll break down the main causes, the risk factors that make some horses more vulnerable than others, and what you can do to help protect your horse's skin naturally.
What Is Mud Fever in Horses?
Mud fever is a skin condition that affects the lower limbs of horses, most commonly around the pastern, heel and fetlock areas. It is caused by the bacterium Dermatophilus congolensis, which thrives in wet, muddy environments. When the skin's natural barrier is compromised through prolonged moisture exposure, abrasion or irritation, these organisms can penetrate the skin and cause inflammation, scabbing and soreness.
Mud fever is not a single disease but rather a collection of symptoms triggered by environmental and skin-health factors working together. That's why prevention and early care are so important.
What Are the Main Causes of Mud Fever?
Several factors work together to cause mud fever. Rarely is it just one thing, it's usually a combination of environmental conditions and the state of your horse's skin.
Prolonged Exposure to Wet and Muddy Conditions
This is the number one trigger. When a horse stands in waterlogged fields or muddy gateways for hours at a time, the skin on the lower legs becomes saturated. Prolonged moisture softens and weakens the skin barrier, making it far easier for bacteria and fungi to enter. Winter turnout on heavy clay soil is a particularly common culprit.
Bacterial and Fungal Infection
The primary organism behind mud fever is Dermatophilus congolensis, a bacterium that lives in soil. In warm, moist conditions (exactly what you find on a soggy horse's legs) it multiplies rapidly. Fungal organisms can also play a role, particularly when the skin stays damp for extended periods. This is why anti-fungal and anti-bacterial protection matters when managing mud fever.
Damage to the Skin Barrier
Anything that breaks or weakens the skin makes infection more likely. Common causes of skin damage include rough or sandy footing, abrasive bedding, repeated hosing without thorough drying, over-washing with harsh products that strip natural oils, and clipping feathers too aggressively. Even small nicks or scratches can give bacteria an entry point.
Standing in Wet Bedding
It's not just the field that poses a risk. Horses stabled on wet or poorly drained bedding can develop mud fever too. If the legs are never fully dry, the conditions for bacterial growth are just as favourable indoors as they are outside.
Why Are Some Horses More Prone to Mud Fever?
Not every horse standing in the same field develops mud fever. Several factors influence individual susceptibility.
Horses with White or Pink Skin
Horses with white legs or pink, unpigmented skin on their lower limbs are statistically more prone to mud fever. Unpigmented skin tends to be more sensitive and more easily damaged by UV exposure and moisture, which lowers its natural resistance to infection.
Heavy Feathering
Breeds with thick feathering around the fetlocks (such as cobs, Shires and Clydesdales) are particularly vulnerable. The dense hair traps moisture against the skin, creating the perfect warm, damp environment for bacteria to thrive. It also makes it harder to spot early signs of irritation before the condition worsens.
Compromised Immune Health
Horses that are elderly, stressed, nutritionally deficient or managing other health issues may have a less robust immune response. This makes it harder for the skin to fight off infection naturally. Supporting overall wellbeing from the inside through good nutrition and appropriate supplementation can make a real difference. A 100% natural feed supplement like Non-Stinky Stuff supports skin health, coat condition and overall wellbeing from within, which can help the skin stay more resilient during challenging conditions.
Horses That Are Frequently Washed
Over-washing or hosing legs without drying them properly afterwards is a surprisingly common contributor. While it might seem helpful to rinse off mud, leaving the legs damp strips natural protective oils and actually increases the risk. If you do wash your horse's legs, always dry them thoroughly afterwards.
Does the Time of Year Affect Mud Fever Risk?
Yes, mud fever is strongly seasonal, with the highest risk during autumn and winter when ground conditions are at their wettest. However, it can occur at any time of year if the conditions are right. Prolonged wet weather in spring, irrigated paddocks in summer, or horses standing in waterlogged areas can all trigger the condition outside of the traditional "mud fever season."
In the UK, the period from October through to March tends to carry the greatest risk, particularly on clay-heavy ground that doesn't drain well.
Can You Prevent the Causes of Mud Fever?
While you can't control the weather, you can take practical steps to reduce your horse's risk. Prevention centres on two key principles: minimising moisture exposure and protecting the skin's natural barrier.
Rotating turnout areas to avoid churned-up ground, using well-drained gateways, and managing stable bedding to keep it clean and dry all help reduce environmental risk. Equally important is protecting the skin directly.
Mud Stuff is a 100% natural barrier balm specifically formulated to help protect your horse's legs from mud, moisture and irritation. It contains naturally anti-fungal and anti-bacterial ingredients â including Nigella sativa (black seed oil), Azadirachta indica (neem), Lavandula (lavender) and Melaleuca (tea tree) â that help shield the skin while keeping it nourished and conditioned. Applied to clean, dry skin before turnout, it forms a breathable, water-resistant layer that supports the skin's natural defences.
For horses prone to itchy, irritated skin more broadly, the Original Stinky Stuff (Ultimate Horse Care Pack) provides a complete 100% natural skin care system that can be used as a massage rub, shampoo wash or even a fly spray â offering versatile support alongside targeted mud fever protection.
When Should You Call the Vet?
If your horse's mud fever is severe  with deep scabbing, swelling, heat in the legs, lameness or signs of spreading infection it's important to consult your vet. Mud fever that doesn't respond to routine care, or that recurs persistently despite good management, may need professional assessment to rule out underlying issues.
Natural skincare can play an important role in day-to-day skin support and prevention, but it's always wise to seek veterinary advice for anything beyond mild, early-stage irritation.
Understanding the Causes Is the First Step
Mud fever doesn't appear out of nowhere. It's the result of environmental factors, skin damage and bacterial or fungal infection working together. By understanding what causes mud fever in horses, you can take meaningful steps to reduce the risk, from managing turnout conditions to supporting the skin with natural, protective care.
If you're looking for a simple, natural way to help protect your horse's legs during the wetter months, Mud Stuff offers 100% natural anti-fungal and anti-bacterial protection in a nourishing barrier balm. It's gentle, easy to apply and designed to support your horse's skin through the toughest conditions.