Thrush: What Is It, Really?

What is thrush?

Thrush is an anaerobic bacteria and fungus found in the intestinal tract of hooved animals, such as horses. “Anaerobic” means that it grows and thrives in the absence of oxygen.

Once thrush gets into a horse’s foot, it attacks the frog, central sulcus, and collateral sulci. In some cases, the infection may also create secondary complications like white line separation or seedy toe, especially if poor hoof hygiene continues.

Although thrush is a somewhat common condition, it shouldn’t be underestimated, and immediate treatment is recommended to prevent the infection from spreading to sensitive tissue.

Thrush-infected hooves will show a thick, black tar like substance that has a very specific foul-smelling odor.

The frog will have a rough appearance as well as looking ragged and unhealthy.

Thrush usually begins as a mild “infection’ and travels into the collateral sulci and the central sulcus and eventually to the entire frog.

If not treated and prevented properly deepseated thrush will attack the sensitive frog, which will create bleeding when the frog is cleaned and lameness may be present.

How bad can it get?

While thrush may appear suddenly, early-stage infections are usually superficial and respond well to prompt care. However, if ignored, thrush can worsen quickly and become deeply embedded in the frog.

In severe cases, untreated thrush can contribute to broader issues with balance and movement. For example, chronic pain or infection in one hoof may trigger compensatory weight shifts that increase the risk of lameness or hoof wall separation.

The following images are examples of what different stages of a thrush infection may look like.

Causes of Thrush in Horses

Many horse owners mistakenly believe that thrush is caused by mud or wet conditions, but that’s only part of the story. Thrush in horses is a bacterial and fungal infection introduced when the hooves come into contact with manure, especially in poorly maintained environments.

How Horses Get Thrush

The bacteria and fungi responsible for thrush naturally exist in the horse’s intestinal tract. When manure accumulates in stalls, paddocks, or hoof sulci, these microbes can enter the central sulcus or collateral grooves of the frog. If the environment is also wet or compacted, oxygen is sealed out—creating the perfect conditions for thrush to grow.

Risk Factors That Increase Thrush

• Deep central sulci that trap manure and moisture

• Narrow or contracted heels that reduce airflow and cleaning

• Club foot conformation or high heels that encourage deep, tight sulci (See more)

• Chronic laminitis or founder, which alters normal hoof balance

• Poor stable hygiene and irregular hoof care routines

Horses with deep sulci or high-heeled hoof shapes are especially vulnerable because their feet don’t self-clean as they move. While thrush can affect a single foot, it's not uncommon to see it in multiple hooves at once.

Note: Thrush is not contagious, but if multiple horses are housed in poorly cleaned or muddy environments, they can all develop it independently.

Best Treatments for Thrush in Horse Hooves

Early-stage thrush is easy to treat if caught in time and managed consistently. Since thrush thrives without oxygen, the foundation of any treatment plan is to expose the bacteria to air through regular cleaning.

Step 1: Daily Hoof Cleaning

Pick your horse’s hooves thoroughly every day, especially the central sulcus and collateral grooves. This breaks up packed-in manure and introduces oxygen to the infection site. Cleaning is more effective than any product if done consistently.

Pro tip: Cleaning alone can kill most early-stage thrush without additional chemicals.

Step 2: Apply a Topical Thrush Treatment

Credit: Barrelhorsenews

After cleaning, use a vet-recommended thrush treatment solution such as:

• Iodine-based antiseptics

• Copper sulfate gels or powders

• Antimicrobial hoof clays

Apply products according to label directions. Inconsistent use—every few days instead of daily—can allow the infection to persist or return.

Step 3: Treat Deep or Advanced Infections

If the central sulcus is deeply infected, it may form a fissure between the heel bulbs, which requires additional care. Soak the hoof in a medicated solution and use cotton gauze soaked in treatment to “floss” between the bulbs. This removes trapped debris and helps the medication reach deeper tissue.

If lameness is present, your vet may recommend:

• Medicated soaking (e.g., in diluted Betadine or Chlorhexidine)

• Protective wrappings with antimicrobial solutions

• A revised trimming plan to address heel contraction or frog damage

Explore this guide if you notice the frog has deteriorated enough to cause wall separation or cavities at the toe.

What Not to Do

• Avoid hoof boots while the horse is at rest. They trap moisture and heat—perfect for thrush to thrive.

• Never use caustic homemade treatments like bleach, peroxide, or strong acids. These can damage live tissue and the coronary band, and may even lead to hoof capsule loss in severe cases.

Contraindications

While there are many effective ways to treat thrush, some approaches can actually make the condition worse. Understanding what not to do is just as important as knowing what works.

Avoid Hoof Boots During Rest

Using hoof boots—especially those with plastic or synthetic linings—can trap heat and moisture around the frog, creating the perfect anaerobic environment for thrush to thrive. Unless your horse is in work or turnout, leave boots off during rest periods. If protection is needed for a sensitive frog, opt for medicated wrappings that allow better airflow.

Hoof boots should never be used as a substitute for environmental hygiene or daily cleaning.

Do Not Use Harsh or Caustic Chemicals

Homemade thrush remedies that rely on bleach, peroxide, or copper sulfate in raw form can be extremely damaging. These substances can burn live tissue, harm the coronary band, and in severe cases, cause the hoof capsule to separate.

Only use products specifically formulated for equine hoof care. Always read labels, and consult your vet or farrier if you’re unsure.

Prevention: How to Stop Thrush Before It Starts

The best thrush treatment is prevention. And prevention starts with daily hoof care, clean environments, and understanding your horse’s individual risk factors.

Clean the Environment

Credit: horsejournals

Remove manure from stalls and paddocks regularly, ideally multiple times per day. Wet or compacted bedding and high-traffic turnout areas should be monitored closely, especially in rainy seasons or humid climates.

Thrush is not caused by mud alone—it’s caused by manure packed into the foot and sealed in by moisture.

Pick Hooves Daily

Routine hoof cleaning is your first and best line of defense. Pay special attention to the central sulcus and collateral grooves, where manure and bacteria tend to accumulate. Horses with deep or narrow sulci need extra care, as these areas don’t self-clean as easily during movement.

Address Hoof Imbalances

Horses with chronic hoof issues like contracted heels, club foot, or high-low syndrome are more prone to thrush due to structural imbalances that promote deep sulci and poor circulation. Regular trimming and conformation-aware shoeing are essential. Learn more about high-low syndrome and its impact on hoof health.

Support Healthy Frog Growth

Encourage movement in turnout, provide a dry resting surface, and ensure your horse’s diet includes essential nutrients for hoof strength. Poor hoof quality can make it easier for the infection to take hold and harder for the frog to recover.

Key Points

• Thrush is a degenerative, anaerobic bacterial/fungus infection of the frog.

  
  

• Thrush is caused by a horse stepping in manure and feet not regularly picked.

• Thrush is not created by mud only, but by manure packed into a foot.

  
  

• Horses that continually walk in manure will be more likely to develop thrush.

  
  

• Without treatment thrush my attack the sensitive frog, creating lameness.

Take the Next Step in Hoof Health

Want to stay ahead of hoof problems like thrush, seedy toe, and wall separation? We’ve got resources that make it easy to learn and apply better care.

✅ Explore Our Equine Study ToolsFlashcards, infographics, and printables to help you master hoof anatomy, infections, and treatment protocols.Browse Hoof Care Tools →

✅ Get Full Access with MembershipJoin Horse Education Online for full access to advanced hoof care lessons, treatment calendars, anatomy visuals, and certification prep.See Membership Options →

✅ Learn More About Related ConditionsUnderstand the connection between frog infections and deeper hoof issues like seedy toe or club foot, and how to catch them early.

Frequently Asked Questions About Thrush in Horses

What does thrush look like in horse hooves?

Thrush often appears as a black, foul-smelling discharge in the grooves around the frog, especially the central sulcus. The frog may look ragged, recessed, or soft, and the infection may cause tenderness or sensitivity when picking the hoof.

Is thrush in horses painful?

In early stages, thrush may not cause obvious discomfort. But as the infection progresses, it can invade deeper tissues of the frog and central sulcus, leading to pain, lameness, and even bleeding during cleaning. Left untreated, thrush can contribute to more serious hoof conditions.

What causes thrush in horses’ feet?

Thrush is caused by anaerobic bacteria and fungi that thrive in wet, manure-packed environments. It’s not caused by mud alone, but rather by organic waste sealed into the hoof. Horses with deep sulci, contracted heels, or poor hygiene are most at risk.

Can you ride a horse with thrush?

If the infection is mild and the horse is not sore, light riding may be safe—but only if treatment is actively underway. Horses with central sulcus fissures, lameness, or sensitive frogs should not be ridden until cleared by a farrier or vet.

What is the best treatment for thrush in horses?

The most effective treatment is daily hoof picking combined with a topical product like iodine, copper sulfate, or antimicrobial clay. In advanced cases, hoof soaking and medicated wrappings may be required. Cleaning must be consistent, as skipping days allows the infection to persist.

Can hoof boots cause thrush?

Yes—when used during rest or in wet conditions, hoof boots can trap heat and moisture, creating the perfect low-oxygen environment for thrush. If boots are needed, use breathable, medicated wraps instead, and keep the foot as dry as possible.

How do I prevent thrush from coming back?

Prevention starts with daily cleaning, a dry and clean living environment, and regular trimming to keep the frog healthy and self-cleaning. Horses with deep sulci or hoof imbalances may need more frequent checks. Learn more in our hoof care and prevention guides.