What is Equine Pastern Dermatitis (EPD) in Horses?

Defining EPD in Horses 

• Equine pastern dermatitis is the giant umbrella term for an assortment of lower leg skin conditions of the horse. You may have heard terms like scratches, dew poisoning, mud fever, and greasy heel, but there are many others!

• EPD is a syndrome, not a specific diagnosis, and has a multitude of possible causes. You will usually see some of the following: scabs, inflammation of the skin, lesions or sores, blisters, lameness (!!), hair loss, redness of the skin, crusty hair, blisters, dry skin or lizard-like skin, itchiness, and even oozing and thickening of the skin. None of this is comfortable for your horse.

• Some vets call milder cases scratches, in which you typically see a bit of inflammation and some scabs. Are they itchy and/or painful? Sometimes. There’s also an element of alopecia (hair loss) involved.

• As things worsen, the skin can start to redden, slough away, and ooze. That ooze, for lack of a less gross term, is technically exudate, which can be more like pus or more like clear fluid, or somewhere in between. There may be blisters, and there’s definitely obvious inflammation. In cases like this, where the condition becomes exudative, it is often referred to as greasy or grease heel.

Complications of Equine Pastern Dermatitis

• Things can get even worse, and for some horrible reason, someone equated this stage of EPD as “grapes,” which almost ruins the whole wine thing for me. This stage is the most severe, and the skin on your horse’s leg can thicken, get scaly, and develop nodules. At this point, things are chronic.

• What makes EPD even more frustrating is that the lower leg’s skin is taut by design, and with every step, the damaged skin, scabs, and sores can flex and stretch, creating cracks in the skin. This process causes a traffic jam in the healing process and makes a lovely entry place for secondary infections to take hold.

• If bugs and flies are present, insect bites can add to the discomfort.

• Lameness, secondary infections, and sensitivity to sunlight are also possible. Advanced cases of chronic progressive lymphedema in horses often result in euthanasia.

Horse A, after EPD has mostly cleared up. 

What Causes EPD in Horses?

• Pull up a chair, we may be here a while. Because EPD is a condition, there are many possible causes. Some overlap, some don’t. To make things more complicated, the clinical signs of every cause of equine pastern dermatitis often appear identical. There may also be different presentations of the cause in different horses.

• Your veterinarian needs a detailed history of your horse’s skin health, as well as information about their diet, living environment, breed, and any other conditions your horse may have, to reach an accurate diagnosis.

Mud fever

• Scratches, greasy heel, mud rash, and dew poisoning all describe the same condition at the back of the pastern. The affected areas suffer from a bacterial infection caused by microbes, wet conditions, and moisture retention by the hair. Some cases also have fungal elements. You will see skin irritation, scabs, and flaky skin and hair. You may see bacteria such as Dermatophilus congolensis and Staphylococcus aureus closely linked to mud fever.

Photosensitivity

This condition often affects horses with white markings and typically occurs when a horse has ingested a reactive weed or has liver issues. The light skin under white hair becomes easily burned in UV light. The skin becomes scabby and literally falls off. Many horses with photosensitivity exhibit behavioral issues when exposed to direct sunlight due to the pain associated with this skin reaction. White legs are particularly susceptible, as are pink noses and blazes, and any other patches of white hair.

More on this fascinating condition here.

There’s also pastern leukocytoclastic vasculitis

• This condition is another UV-related condition. Your horse’s immune system is part of the issue here, and it will damage the blood vessel walls from within your horse’s body. This damage creates sores, which amplify with UV light. There may also be allergies involved in this condition.

Chorioptes Mites and Mange

• If you have ever seen one of those tear-jerking photos of a stray dog with barely any hair and scaly skin, you have likely seen mange in full force. Horses are also susceptible to mange, caused by choriotes mites. These tiny insects live on the skin, and especially love any population of horses with feathered legs. They create intense itching, crusty scales, and hair loss. You may see your horse biting and rubbing their legs for relief. It’s also possible for these mites to reside in the tail and other spots on your horse, and they are confirmed with a skin scraping.

Allergies

• There are as many causes of allergies as there are horses in the world. Is it the grass? Is it a fabric or a component of your horse’s sport boots? Detergent that you wash them in? A food allergy? Fly spray? Dust? Pollen? As we know from previous discussions about allergies, it’s essential to conduct blood and/or elimination tests to identify potential triggers.

Folliculitis

• This is a fancy way of saying infected hair follicles. The infection could be caused by bacteria, which are literally present on and in every single thing on the planet. There’s also a chance of a ringworm infection, which is not a worm but a fungus instead. Still no answer about why they can’t change the name to ring-fungus or something more logical.

Chronic progressive lymphedema (CPL)

• CPL is an ongoing condition of the lymphatic system and is usually found in draft breeds. It creates drainage problems, which lead to swelling, skin folding, and secondary infections from skin lesions. It can also cause lameness and pain, severely impacting a horse’s quality of life. While genetic factors play a role in the chronic form of lymphedema in the lower limbs, environmental factors also contribute to a horse’s progression of this disease.

Proud flesh

• During wound healing, especially on the lower leg, there’s a risk of excessive granulation tissue, commonly referred to as proud flesh. As the healing part of the wound begins to take over, the surrounding skin is unable to knit together and fully heal the wound. Early treatment and diligent care of even the most minor wound on the legs can help prevent this.

Read more about proud flesh here from the AAEP.

Horse B after treatment for EPD.

Work With Your Vet on EPD

• Your vet needs to help you figure out the root causes of your horse’s equine pastern dermatitis. There’s no use spinning your wheels using diaper rash ointment as a skin barrier cream or some other home remedy when the cause may be internal, sunlight-related, fungal, or bacterial. The goal is to prevent a minor case from turning into a severe case.

• The same applies to picking or not picking scabs. Picking scabs is not only painful for your horse, which is a perfect way to lose a willing patient, but it can also open the damaged tissue to new infections and bacteria. Your vet should provide you with a comprehensive plan that includes handling scabs.

• Know thine scab-causing enemy before you start hurling all the random (and questionable) stuff that non-doctors toss around. Someone else’s idea for handling dermatitis is actually making it worse.

Determining the cause of equine pastern dermatitis

• Thankfully, your vet has gobs of tools and tests to help narrow down the cause of your horse’s troubles. It starts with you, giving your vet all of the deets about what you noticed, when, and under what conditions. Are things itchy? Oozing? Cracking open? What has the weather, footing, and mud been like? Are you meticulous about dry stalls or meh?

• There are lab tests that can be performed, such as a superficial skin scraping. This simple procedure looks for mites and mange. Or your vet may take a hair or skin sample for biopsy. Allergy tests, organ function tests, and even basic blood work to check for the presence of infections can all be performed. Blood testing to uncover underlying causes, such as liver disease, helps you vet get a more detailed look at the influencing factors.

Horse C after treatment.

What Makes Equine Pastern Dermatitis More Likely in Horses?

• There is an association between skin problems and both environmental factors and genetics.

Environmental conditions

• Logically, damp, wet, and muddy conditions trap questionable soil and poop and whatnot next to your horse’s skin. Damp and dirty is like a petri dish of bad potpourri growing on your horse. Will every horse with muddy legs get EPD? No, but it can play a role.

• One of the major predisposing factors to EPD is prolonged exposure to mud, which is why so many horses suffer from mud fever most dramatically during wet months.

• There’s a point at which your horse’s bedding, pasture, turnout, and even arena footing can influence the health of the skin on his legs. It’s not always mud. There can be smaller contributing factors. Bedding and footing are just two of them!

• Allergens are another environmental factor to consider. Bedding, grooming products, grasses, pollens, and commercial grain ingredients can all trigger allergies.

Genetics

• A horse’s genetic makeup can influence their allergies, immune system, the likelihood of developing an autoimmune condition, and even how much sebum they make. Genetics is also related to CPL and feather mites, as well as the susceptibility of these breeds to developing these conditions.

Feathers

• Closely linked to genetics is your horse’s lower leg hair. Is it feathered or not? Some feathered horses trap moisture and carry on their own scab-inducing science experiments in excessive hair. Some are not. It’s the veterinary consensus that feathers seem to complicate equine pastern dermatitis instead of warding it off. While it’s nice to honor your horse’s breed and traditional characteristics by keeping feathers, it might be wise to keep them clipped or shortened if equine pastern dermatitis is something you battle.

Diet

• It’s not just allergens that can live in your horse’s diet. There are aspects of diet, such as certain plants in pasture, that can create photosensitivity. Or, your horse’s diet is missing some key ingredients that support skin and coat health and immune support. There’s a lot to be said about Omega-3 fatty acids and vitamin E in this respect. An equine nutritionist is your best source for ensuring your horse’s diet is suitable for their health.

Treatments For Equine Pastern Dermatitis

• Finding the best treatment can take time, as the skin microbiota of your horse may differ from another with the same condition.

Do or don’t change too many things at once

• It’s tempting to make every change possible to your horse, which may not always be a good thing. If you are trying to determine possible allergens, you’ll need to strip their diet and environment down to the basics and slowly add one possible allergen at a time to pinpoint the most likely triggers.

• In other cases, it’s best to adjust your horse’s diet with the help of your equine nutritionist or veterinarian, and start trying different topical medications, changing turnout patterns, and identifying possible allergens to reduce your horse’s pain as quickly as possible.

Memorize your horse

• As with everything, your hands and eyes are the first and best things to use to notice your horse’s changes. Giving your horse the once-over with a brush won’t give you the same information as using your eyes and hands.

Leave the detergents for the laundry room

• Detergents (like dish soap) and harsh shampoos strip away grease. That includes the very precious sebum that your horse makes to protect their skin. Fun fact about sebum – aside from being antimicrobial, it’s a natural stain repellent, so when you let it build up, everything is easier to clean. It also waterproofs your horse and boosts shine.

• Plain water rinsing can do more to clean tissue and help healing than harsh detergents. Gently rinse, never scrub, the poor, injured skin, and use clean towels to help the area dry.

Use a barrier method to protect your horse’s legs

• Just as using a sheet the night before a show to keep your horse clean, use socks to provide a barrier to outside forces on your horse’s legs. 

• The antimicrobial silver in some horse sock yarn separates the damaged skin tissue from outside hazards, whether they be allergies, bacterial sources, or fungal infections, and the socks can protect the skin from UV sensitivities.

• Even if you can figure out what allergens are causing your horse to suffer, it may be impossible to remove those allergens from the environment or move your horse to another location.

• Fly boots are another option for protecting against the sun, insects, and mud.

Yes, horses can wear socks.

Fight from all other directions for the best chances of healing EPD

• Use clean brushes, clean polo wraps, and clean sport boots. And saddle pads and tack, for that matter.

• Get diligent about poop pick-up. Bacteria like E. coli, among dozens of other bacteria, live in manure. It’s tempting to skip cleaning larger dry lots and paddocks, but once you get into a daily routine, it becomes easy. This habit also helps prevent intestinal parasites from multiplying among the horses in the barn. And it keeps flies away. SO MANY good reasons to do all of the scooping.

• Keep your horse’s bedding clean. Whatever method you use, the barely-there shavings or the deep litter system, keep it all fresh.

• Check if your horse’s turnout schedule can accommodate the morning dew. If photosensitivity is a problem, use socks, boots, and/or a night turnout schedule to keep the UV rays off your horse.

• Some treatments can help your horse with EPD, but narrowing down the cause is crucial. There’s no use in using antibiotics if UV light is the primary factor. Just as there’s no use in treating an allergy with a different turnout schedule.

Treating equine pastern dermatitis is a marathon, not a sprint, with multiple stages and approaches. Work with your vet from the very beginning. Tackle all possible angles of triggers.

Horse A before.

Before, Horse B

Horse C before.