Key Insights
  • Horses do not develop true keloids but may form proud flesh, an overgrowth of granulation tissue in wounds
  • Proud flesh arises when wound healing is disrupted by tension, infection, or excessive movement
  • Lesions appear as raised, spongy tissue that extends above the wound and bleeds easily when disturbed
  • Larger horses and lower limb wounds are most prone to developing excessive granulation tissue
  • Diagnosis is based on wound appearance, delayed closure, and tissue texture evaluation by a veterinarian
  • Treatment includes surgical removal, topical corticosteroids, and proper wound cleaning and bandaging
  • Preventing proud flesh requires early care, infection control, and restricted movement during healing

Keloids are an overgrowth of scar tissue that forms at the site of an injury in humans, extending beyond the original wound boundaries. They are dense, fibrous, and typically raised, smooth, and shiny in appearance. [1]

While horses do not develop true keloids as seen in humans, a similar condition known as proud flesh (Exuberant Granulation Tissue), is commonly referred to as keloids by horse owners.

Proud flesh occurs when the normal wound healing process is disrupted, leading to an overgrowth of tissue that extends above the skin’s surface and hinders proper wound closure. [2][3] This condition is most commonly seen in the lower limbs and can be triggered by factors such as movement, tension, and delayed healing.

To help prevent proud flesh, it’s important to provide appropriate wound care, minimize movement, and manage tension, especially in areas prone to irritation. If your horse shows signs of proud flesh, consult a veterinarian for a proper assessment and treatment plan.

Do Horses Develop Keloids?

A keloid is a raised scar that forms due to excessive collagen production during wound healing.

Unlike normal scars, keloids grow beyond the original wound boundaries and do not shrink over time. They are dense, fibrous, smooth, and raised, often linked to genetic or biochemical factors. [1][4]

Horses do not develop keloids in the same way that humans do. Instead, they are prone to “proud flesh,” or exuberant granulation tissue (EGT). Proud flesh is an overgrowth of granulation tissue within a wound that extends above the skin’s surface, forming a soft, spongy mass. This excessive growth halts the healing process by preventing the wound from closing. [5]

Unlike hypertrophic scars, which stay within the wound boundaries, EGT protrudes beyond the wound edges, behaving like a benign tumor. Research indicates that fibroblast cells in EGT, similar to those in human keloids, exhibit enhanced proliferation, collagen production, and cytokine activity. [5]

Abnormal wound repair mechanisms drive proud flesh formation. Fibroblasts overproduce extracellular matrix (ECM) and collagen, failing to transition into inactive fibrocytes or undergo programmed cell death (apoptosis). This disrupts the normal healing cycle and traps the wound in the proliferative phase. [5]

While keloids are chronic and often linked to genetic predisposition in humans, proud flesh in horses arises primarily from mechanical factors like movement, tension, or delayed healing – especially in wounds on the lower limbs. With proper care, proud flesh can typically be resolved, unlike the persistent nature of keloids. [6]

Proud Flesh in Horses

When an injury occurs, the body initiates a complex process to repair the damaged tissue.

This process typically progresses through three stages: [4][7][8][9]

  • Inflammatory Phase: The initial phase begins immediately after injury. During this phase, the body stops the bleeding through clot formation and cleans the wound with immune cells like neutrophils and macrophages. These cells clear debris, fight infection, and release cytokines and growth factors that attract and activate specialized repair cells.
  • Proliferation Phase: This phase focuses on building new tissue. Fibroblasts produce collagen, and new blood vessels form to nourish the area. Granulation tissue fills the wound, and epithelial cells begin migrating across the wound bed to close it.
  • Remodeling Phase: The final phase, lasting months to years, strengthens and matures the tissue. Collagen fibers are reorganized, and the wound shrinks as a scar forms. Although the tissue becomes stronger, it rarely regains its original strength.

In horses, when the proliferative phase is prolonged or poorly regulated — often due to movement, infection, or tension — this process can lead to the overproduction of granulation tissue, resulting in proud flesh.

Signs of Proud Flesh

Proud flesh, or exuberant granulation tissue (EGT), typically appears as a raised, irregular mass that protrudes above the original wound edges. It often has a soft, spongy texture and can be red or pink due to increased blood flow in the area. [4][5]

The tissue may appear moist and may bleed easily as it is very vascular, especially if disturbed. Unlike normal healing tissue, proud flesh grows beyond the boundaries of the wound, preventing the proper closure of the wound and halting the healing process. [5]

It may have a fleshy or rubbery feel and, in some cases, can become firm over time. If left untreated, it can lead to further complications, including infection and delayed wound healing. [5]

Causes

Proud flesh occurs when the proliferation phase of wound healing is prolonged or poorly regulated. In such cases, fibroblasts overproduce extracellular matrix (ECM) and collagen.

Instead of transitioning into inactive fibrocytes or undergoing programmed cell death (apoptosis), these fibroblasts remain active, resulting in the excessive growth of granulation tissue. [5]

Normally, granulation tissue forms a scaffold for new skin cells to close the wound. However, when it grows excessively, it extends above the wound and blocks the movement of skin cells, preventing proper closure. This delays healing and creates a cycle where the wound remains open, leading to complications like proud flesh. [3]

The risk of proud flesh underscores the importance of effective wound management in preventing complications and promoting proper healing.

Risk Factors

Proud flesh (exuberant granulation tissue) in horses is more likely to develop under certain conditions, particularly when wound healing is disrupted.

Several risk factors increase the likelihood of excessive granulation tissue formation in horses, including: [2][4][6]

  • Body Size: Larger horses are more prone to developing proud flesh, while ponies are rarely affected. The size and body condition of a horse can influence the wound healing process, making larger horses more susceptible to complications such as excessive tissue growth.
  • Wound Location: The location of the injury plays a significant role in the development of proud flesh. Wounds on the lower legs are at higher risk.
  • Rate of Healing: Injuries that involve tendons, ligaments, fascia, or bone often heal more slowly as these tissues have limited blood supply. The extended healing period increases the chance of abnormal tissue growth.
  • Movement and Tension: Movement, particularly around joints or tendons, can interfere with the healing process. Sliding tendons or constant joint movement can pull on the wound, preventing the formation of healthy tissue and promoting the growth of excessive granulation tissue.
  • Infection: An infection can significantly delay wound healing and create an ideal environment for the growth of proud flesh. The presence of bacteria can increase inflammation and disrupt the normal progression of the wound healing phases.
  • Inadequate Wound Management: Improper cleaning, lack of protection, and delayed interventions can contribute to the development of proud flesh.

Timely and effective intervention, along with proper wound management, can help reduce the risk of proud flesh in horses, leading to more favorable healing outcomes.

Diagnosis

Diagnosis of proud flesh (often mistakenly referred to as keloids) in horses is primarily based on the appearance of the wound and surrounding tissue. Proud flesh is characterized by excessive growth of granulation tissue that extends above the skin’s surface, preventing the wound from healing properly. [2][10]

The veterinarian will evaluate the wound’s progression and examine the tissue’s texture. It is typically soft, spongy, and irregular, often resembling a cauliflower or lumpy mass. In addition to the visible characteristics, the veterinarian will consider whether the tissue has been bleeding or oozing, as proud flesh is highly vascular and prone to bleeding when disturbed. [10]

Diagnosis is further supported by noting the failure of the wound to close and heal normally, as proud flesh often hinders the natural epithelialization (closure) of the wound. A history of delayed healing, trauma, or tension in the affected area also helps guide the diagnosis. [10]

In some cases, the veterinarian may take a sample for further testing to rule out infection or other complications that could contribute to the growth of exuberant granulation tissue. [10]

Intro to Equine Nutrition
Gain a deeper understanding of your horse's nutrition needs. This free introductory course provides a foundation for horse owners to learn how to balance your horse's diet.
Enroll Now
Introduction to Equine Nutrition Course - Mad Barn Academy

Treatment

Treatment for proud flesh (exuberant granulation tissue, EGT) in horses focuses on managing the overgrowth of tissue and promoting proper wound healing. Treatment methods can vary depending on the severity of the condition. [2][3]

It’s important to work closely with a veterinarian to monitor the wound, apply appropriate treatments, and make adjustments based on the horse’s response to therapy. Early intervention is crucial to preventing complications and ensuring the best possible outcome.

Surgical Removal

Surgical removal is often the first-line treatment for proud flesh when it becomes excessive. In this procedure, a veterinarian carefully excises the overgrown granulation tissue, leaving healthy tissue at the wound site. [11]

The goal of excision is to remove just enough of the proud flesh to allow the wound to heal properly while maintaining as much healthy tissue as possible to support the wound closure. [11]

Surgical removal is usually performed under standing sedation. However, the procedure may depend on the location of the wound and the size of the tissue that needs to be excised. While this method is highly effective, it requires careful monitoring afterward to prevent the proud flesh from regrowing. [2]

Following surgical removal, the wound should be properly managed to promote healing. This includes aseptic preparation of the wound site, followed by sterile bandaging and the application of topical antibacterial treatments or antiseptic dressings. [11]

Topical Medications

Topical treatments, such as corticosteroids and other anti-inflammatory ointments, are used to manage the inflammation and excessive growth of granulation tissue in horses. These medications help reduce inflammation, control tissue overgrowth, and promote proper healing. [2][4][11]

Caustic Substances

Caustic substances are sometimes used as a treatment method for proud flesh in horses, but this approach is generally not recommended by veterinarians as they can delay the healing process. These substances are often mistakenly applied by horse owners as a quick fix for proud flesh, but they can cause significant harm to the wound’s healing environment. [2][11]

Substances like copper sulfate, silver nitrate, nitric acid, lye and various other home remedies work by chemically burning or necrosing tissue. While they may reduce the visible mass of granulation tissue in the short term, they often cause more harm than good by interfering with the natural healing process.

Consult a veterinarian before attempting to treat proud flesh at home. Not only do caustic substances interfere with healthy healing processes, they are painful for the horse.

 

Prevention

Horses are particularly at risk of developing keloid-like scars when they sustain wounds on their lower limbs, especially if not properly managed. To reduce the risk, follow these steps: [2][10]

  • Proper Wound Care: Clean the wound immediately with a mild antiseptic to remove dirt, debris, and bacteria. Early cleaning helps reduce the risk of infection and excessive granulation tissue. Ensure the wound remains clean and dry during healing. Regularly check the bandage to prevent moisture and dirt from increasing infection risk.
  • Sterile Bandaging: Apply a sterile bandage after cleaning to protect the wound and maintain a moist environment that promotes healing.
  • Minimize Movement and Tension: Limit movement and tension on the lower limbs with bandages, wraps, or boots. In some cases, stall rest or a controlled environment may be necessary to support proper healing.

Early intervention is key in preventing granulation tissue from progressing into proud flesh. If granulation tissue begins to grow excessively, timely treatments such as surgical excision or corticosteroid application can help manage the overgrowth and promote proper healing.

Regular monitoring of wounds is essential to detect signs of abnormal tissue growth early, allowing for prompt intervention before the condition worsens. If there are concerns about excessive granulation tissue, it’s important to contact a veterinarian for guidance and appropriate treatment.

Frequently Asked Questions

Here are some frequently asked questions about keloids in horses:

Summary

Horses cannot develop true keloids but can experience proud flesh, which is an overgrowth of granulation tissue that disrupts the healing process, especially in lower limb wounds.

  • Proud flesh develops when the normal wound healing process is disrupted, causing excessive collagen production and fibroblast activity that prevents proper wound closure
  • Proud flesh appears as a raised, spongy mass above the wound's edges, is highly vascular (often red or pink), and can bleed easily
  • Treatment involves surgical excision of excessive tissue, topical medications like corticosteroids to reduce inflammation, and proper wound care to prevent tissue regrowth
  • Timely wound care, including cleaning, bandaging, and minimizing movement, is crucial to prevent proud flesh
  • Regular monitoring allows for early intervention and helps avoid complications
Related Articles
Is Your Horse's Diet Missing Anything?

Identify gaps in your horse's nutrition program to optimize their well-being.

References

  1. Betarbet U. and Blalock T.W., Keloids: A Review of Etiology, Prevention, and Treatment. J Clin Aesthet Dermatol. 2020.
  2. Munroe G. et al., Wound: granulation tissue management in Horses (Equis) VetLexicon.
  3. Anantama N.A. et al., The Granulation (t)Issue: A Narrative and Scoping Review of Basic and Clinical Research of the Equine Distal Limb Exuberant Wound Healing Disorder. The Veterinary Journal. 2022.
  4. Harman R.M. et al., The Horse as a Model for the Study of Cutaneous Wound Healing. Advances in Wound Care. 2021. View Summary
  5. Theoret C.L. et al., Equine Exuberant Granulation Tissue and Human Keloids: A Comparative Histopathologic Study. Veterinary Surgery. 2013.
  6. Ribeiro G. et al., The Best Protocol to Treat Equine Skin Wounds by Second Intention Healing: A Scoping Review of the Literature. Animals (Basel). 2024. View Summary
  7. Winkler, K.P. and Carnevale, J. General Principles of Wound Healing in Small Animals. Merck Veterinary Manual. 2023.
  8. Winkler K.P., Wound Management - Special Pet Topics. Merck Veterinary Manual. 2024.
  9. Wise L.M. et al., Anti-Fibrotic Actions of Equine Interleukin-10 on Transforming Growth Factor-Beta1-Stimulated Dermal Fibroblasts Isolated From Limbs of Horses. Front Vet Sci. 2020. View Summary
  10. Vetfolio and Vetstream Ltd, Proud flesh in Horses (Equis). VetLexicon.
  11. Wilmink J.M. and Van Weeren P.R., Treatment of Exuberant Granulation Tissue. Clinical Techniques in Equine Practice. 2004.