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What You Need to Know About Pastern Dermatitis

August 03, 2022 10 min read

pastern dermatitis case study

Pastern dermatitis has many different names. You may also hear it called mud fever, greasy heel, dew poisoning, scratches, or even scurf. It develops when bacteria, fungi, and/or parasites enter through the topmost layer of the skin, leading to inflammation, pus, and even lameness. While there are many different reasons why this may happen, continued exposure to mud and moisture is the biggest one. Mud causes miniscule abrasions in waterlogged skin that are prime opportunities for bacteria and fungal spores to get past your horse’s natural defenses.

Why is the pastern so susceptible to equine pastern dermatitis? Its unique location means that it is constantly exposed to mud, urine-soaked shavings, manure, rocks, and sticks. The back of the horse’s heel creates a natural “cup” where water and possible chemical irritants, like fly spray, will linger for a longer period of time. 

What are the Symptoms of Pastern Dermatitis?

Pastern dermatitis starts out innocently enough. You’ll see a few small patches of hair loss around your horse’s pastern. These patches may start as a simple thinning of the coat, nearly unrecognizable as one of the symptoms of scurf in horses. 

Soon after the hair loss, scabs will begin to develop on the bare patches of skin. At first, they may appear just like another piece of mud. But if you try to remove these scabs, your horse will be very sensitive and start to bleed. After some time passes you’ll notice the scabs grow bigger. 

Next, look for a clear ooze coming from underneath the lesions. This serum is why scratches also has the nickname “greasy heel.” After you notice oozing, white or yellow pus will start to develop. This pus can harbor a mud fever-causing bacteria, like Dermatophilus congolensis or Staphylococcal spp. 

Now your horse’s pasterns have become a battlefield. The immune system is flooding the area with white blood cells in an attempt to overcome the infection. As the symptoms of mud fever progress, the legs may start to swell and become hot to the touch. 

A moderate to severe pastern dermatitis infection can be difficult to beat. If left untreated for too long, your horse can actually go lame. Early detection is key to a full and fast recovery.

What Causes Scratches?

In order to successfully manage your horse’s pastern dermatitis, it’s important to get to the root cause of the issue in order to get your horse back to full health. There are several different ways you can discover what could be causing your horse’s dermatitis. 

Review Your Horse’s Medical History

Dig deep into your horse’s history with your vet. Knowing what month the issue began, what treatments you have already tried (including home remedies), and a detailed description of your horse’s environment is key. The cause of your horse’s equine pastern dermatitis could be right there in his past. 

Examine Your Pasture for Phototoxic Plants

Has your horse been grazing on clover pastures, or exposed to St. John’s Wort, Buckwheat, and Ryegrass? These plants can cause a molecular reaction when UV rays reach the skin. This reaction, known as photosensitization, results in inflammation and skin irritation. It will appear as a severe sunburn. If you believe your horse is suffering from photosensitization, take a look at their muzzle, as their nose would be impacted as well. 

Look for Mites

Equine pastern dermatitis could also be a reaction to mites. Mites cause several different types of mange in horses, most commonly near the pastern due to the presence of feathers. Horses with dermatitis from mites stomp their feet, rub one fetlock against the other, or rub the leg on various objects. You can easily discover if mites are causing your horse’s pastern dermatitis by asking your vet to take a skin scraping. 

Change Your Stable Management Practices

One cause of pastern dermatitis is consistent exposure to moisture and dirt. Your horse’s dermal barrier is weakened when it is soft and waterlogged, which makes it more susceptible to skin irritation. Before taking more invasive measures to find the root cause of your horse’s pastern dermatitis, evaluate how you manage your horse’s stable and find ways to eliminate exposure to additional moisture. 

Perform a Biopsy and Culture

If you haven’t found the cause of your horse’s dermatitis by this step, it might be time for a biopsy. A biopsy and culture tells you if the condition is related to Staphylococcus spp and Dermatophilus congolensis bacteria.

There is some debate as to whether or not Dermatophilus congolensis and Staphylococcus spp cause pastern dermatitis or are merely opportunistic bacteria that cause secondary infection and prolong the healing process. D. congolensis is known to live benignly on your horse’s skin in minimal to moderate quantities. However, given the right conditions, it breeds rapidly, spreading and causing an inflammatory response from your horse’s immune system. 

Whether it causes pastern dermatitis or evolves as a secondary infection, understanding if/which bacteria is present on your horse’s skin can help you develop an effective treatment plan. 

Why Do Some Horses Get Scratches More Often Than Others?

Certain breeds of horse are more susceptible to pastern dermatitis. This can be due to genetics, metabolic issues, allergies, or even feathering. For example, the heavy feathering on the legs of draft horses or friesians makes them more susceptible. This is because the feathers act as a barrier preventing sunlight and oxygen from reaching the skin. Heavy feathering also absorbs moisture and is much slower to dry without the help of a dedicated owner. If your horse has feathers, it’s suggested you clip their legs or take extra precautions when grooming. 

Gray horses or horses with white leg markings are also predisposed to skin disorders, including pastern dermatitis. Many horse owners are aware that light-colored horses are more likely to develop melanomas and sarcoids, but fewer equestrians know that gray horses are also more likely to suffer from dermatitis.One study found that gray horses or horses with white leg markings were nearly three times more likely to suffer from pastern dermatitis than horses of a darker coat color.  

What NOT to Do to Treat Pastern Dermatitis

When treating scratches, scurf, or pastern dermatitis, you may be tempted to curry off all the scabs. The opposite is actually true– aggressive grooming actually irritates the skin even more. Picking off the scabs is very painful for your horse and just leaves larger openings for bacteria to breach the skin barrier and cause more problems, such as secondary infections like cellulitis. Remember the number one rule: don’t scratch scratches.

A common home remedy for pastern dermatitis is to use diluted bleach. Bleach is not designed to be used on anyone’s skin, no matter the species. Sure, it will kill any bacteria or fungal spores on your horse’s skin, but it will also damage good cells and healthy organic matter, which will only prolong your horse’s scratches infection. 

Similar to bleach, hydrogen peroxide is a great sanitizer and bleaching agent. However, the days when it was advisable to use it as a wound cleanser are long gone. Hydrogen peroxide irritates the skin and prevents wounds from healing. If you wouldn’t use it on a wound, then you shouldn’t use it on equine scratches.

Some horse owners will use over-the-counter cortisone when managing equine scratches. In truth, hydrocortisone ointments and creams can be very useful in many aspects of horse care and may even be recommended by your veterinarian. However, most equestrians fail to realize that even non-prescription hydrocortisone is still a steroid. If used too close to the start of a competition, it could cause your horse to test positive for drug use.

One of the most repeated “horse hacks” of all time, yellow listerine is supposed to be the answer to a wide variety of equine skin issues. The minty freshness of menthol and methyl salicylate may taste great in our mouthwash, but can cause stinging when used on wounds. The alcohol will kill bacteria, but also dry out the skin and make it harder for the wound to heal. 

Another home remedy touted on equine forums, white vinegar and rubbing alcohol is definitely not recommended for use on pastern dermatitis. This combination will drastically dry out your horse’s skin, reducing its ability to heal and further weakening the dermal barrier. Both the vinegar and alcohol cause stinging sensations when they come in contact with open wounds, making this tip for managing equine scratches not only very uncomfortable and painful for the horse, but dangerous for the horse owner as well. Any home remedy that causes your horse pain is not only unfair to the horse, but can cause injury to the owner as well if the horse reacts by kicking or striking out. 

Try Changing Your Stable Management Practices Instead

Scratches thrives in wet and unsanitary conditions. Unfortunately, creating clean and dry conditions on a farm can feel impossible. Luckily, there are a few easy steps you can follow to improve your horse’s living conditions. 

Cold, frosty mornings and dewy summer sunrises both create wet conditions that weaken your horse’s natural defenses against bacteria and fungi. Moisture collected on blades of grass is easily transferred to your horse’s lower legs. But, keeping your horse inside can also be harmful if stalls are not cleaned thoroughly or often. If your horse lays down in urine-soaked shavings, bacteria-filled moisture is pressed closed to your horse’s legs and against their skin.

To avoid wet environments, you can:

  1. Turn your horses out after the dew/frost has dried and before it forms overnight.
  2. Keep paddocks mowed short, so the grass cannot reach your horse’s fetlocks.
  3. Clean stalls thoroughly, being sure to strip them of all bedding as needed.

In some barns, it’s common practice to share equipment between horses. When you share brushes and saddle pads, you’re transferring bacteria and microscopic fungal spores from one horse to another. This allows the bacteria and fungi that cause pastern dermatitis to spread like wildfire. This situation is worsened when brushes are not cleaned regularly. Brushing your horse with a dirty brush allows bacteria to enter small abrasions in the skin. Ensure that each horse has their own dedicated equipment and all grooming tools are cleaned often. 

Long feathers and winter coats trap moisture and fungi close to the skin, take longer to dry, and inhibit airflow. This creates the perfect environment for bacteria and fungi to grow and invade your horse’s dermal barrier. 

This problem is exacerbated when riders wash their horses' legs often. Overbathing your horse’s legs strips the skin of its natural protective oils, as well as creates a wet environment. This paves the way for scratches to develop on the waterlogged and weakened skin.

Practice good hygiene by:

  1. Clipping your horse’s legs to allow for more airflow and prevent fungi from growing.
  2. Using dedicated brushes, tack, or equipment for each individual horse.
  3. Washing your grooming equipment at least once a month.
  4. Bathing your horse only when necessary.

Should You Bathe a Horse with Scratches?

As part of caring for a pastern dermatitis infection, your vet will most likely recommend that you keep the area clean and dry. Many horse owners would be tempted to increase their horse’s bathing frequency in order to follow the vet’s instructions. After all, the best way to clean your horse’s legs is with a nice, soapy bath. Unfortunately, pastern dermatitis can be caused by overbathing and worsened by excess moisture. So, should you or should you not bathe a horse with scratches?

When we bathe a horse to clean a condition that’s related to excess moisture, we’re actually introducing more moisture to already-weakened skin. This softens the skin further and decreases the horse’s natural defenses. 

When you bathe your horse, you’re stripping their skin of its natural oils which can actually weaken the protective dermal barrier. Then, if the horse is left to “air dry” or turned back out into the wet environment after a bath, like a dirty stall or muddy pasture, the legs will never dry out, which is essential when treating pastern dermatitis. 

For horse owners who keep their horse in a stall, they may not need to resort to bathing and can therefore avoid drying the skin and wetting the legs. But horse owners who have their horse on field board or pasture board will have a sisyphean job in front of them when it comes to keeping mud off of their horse’s pasterns. 

Forget using bandages to create a protective barrier between mud and your horse’s skin. On a pasture-boarded horse, these wraps may become soaked and unwind, creating a hazardous situation. Or dirt and debris can become trapped underneath the bandages and further irritate the skin. So if your horse doesn’t have a stall, now what? Here is where bathing a horse with scratches or scurf can be beneficial. 

The solution to the conundrum is to carefully and properly bathe your horse in order to solve the infection, not worsen it. You should not curry or pick aggressively at pastern dermatitis as it could worsen the infection; bathing is a good gentle alternative. Gentle water pressure can take off already-loose scabs and loosen others without aggressive currying or picking. Plus, the water will more thoroughly cleanse the area than a curry comb alone. 

Horse owners must use mild soaps that are non-toxic and non-irritating only. Harsh astringent soaps like povidone-iodine and chlorhexidine will only dry out the skin, stripping it of its natural oils, further weakening the protective dermal barrier. Instead, use warm water and a mild soap or saline solution to gently cleanse the area. Do not scrub or use an abrasive sponge to rub at the pastern dermatitis. Your own fingers or a soft, gentle sponge is best. Your goal is not to pick off all of the scabs and crusting caused by scratches. You want to work slowly and carefully to gently remove already-loosened scabs and ensure the area is as clean as possible.

Taking care of your horse after the bath is just as important as what you do during the bath. Use a soft clean towel to dry the infected area as thoroughly as possible. You want to ensure that the pastern is dry down to the skin, not just the hair. It’s also a good idea to dry the entire leg as well, to ensure that water won’t drip down off the leg and onto the pastern. When it comes to pastern dermatitis, the aim of the game is to be as gentle as possible. Don’t irritate the skin further with vigorous rubbing. 

After your horse is clean and dry, use a barrier cream over the scratches infection before turning the horse back out to pasture. This way, if your horse does get muddy, the barrier cream will be there to provide a layer of protection between your horse’s skin and environmental contaminants. 

Equine Pastern Dermatitis & Skin Health

The products that you use on your horse’s scratches, scurf, or pastern dermatitis must be non-toxic, non-irritating, and safe. Look for products that are science-backed, like Zarasyl Equine, which uses orthosilicic acid to promote skin health in horses. 

Orthosilicic acid is the bioavailable form of silicon associated with healthy connective tissue growth. Zarasyl contains a proprietary amorphous silica with a molecular structure tailored to provide sustained delivery of orthosilicic acid to the skin.

Click here to discover how veterinarians and Zarasyl customers have used our barrier cream on pastern dermatitis cases with positive results.