Chestnuts and Ergots on Horses

Kaela Schraer, DVM
By Kaela Schraer, DVM on Aug. 4, 2023
Dressage horse legs

What Are Chestnuts on Horses?

Ever wonder what the hard callouses on the inside of your horse’s legs are for? Chestnuts on horses can be found on the inside of forelimbs above the knee, as well as below the hocks of hind legs. A horse’s chestnuts are much like human fingerprints in that each one is unique. Chestnuts also grow over time similar to human fingernails.

As horses evolved, they traded the stability of having multiple toes for a single very long toe that gives them the ability to reach much higher speeds. During the evolution process, the other toes (like those found in dogs and people) shrank down and in many cases disappeared. The chestnut, a calloused area on the inside of the horse’s forelimb, is leftover evidence of this process. The chestnuts are made of keratinized skin that slowly grows and sheds over time.

Horse chestnuts are also known as “night eyes.” It was once believed that chestnuts helped a horse see in the dark. Most breeds of horse have chestnuts on all four limbs, but some horses are missing chestnuts on their back legs, such as the Icelandic horse.

Horse chestnuts are also known as “night eyes.” It was once believed that chestnuts helped a horse see in the dark.

Can Horses Feel Their Chestnuts?

As keratinized skin, horses cannot feel the top surface of the chestnut. However, they can feel where they attach to the skin beneath. In this way they are very similar to fingernails.

What Is the Purpose of Chestnuts on Horses?

Chestnuts no longer serve a specific purpose in horses. There is some evidence that shows chestnuts may help with limb positioning when the horse is in motion, but the research in this area is not fully developed.

If you get up close to a chestnut and take a sniff, you’ll notice that they are quite odorous, giving off a strong “horsey” smell. An old cowboy trick involved keeping a shaved off part of a horse’s chestnut in their pocket so other horses would become interested in and more friendly toward the cowboy. Perhaps this ploy helped cowboys attract and tame wild horses back in the day.

What Are Ergots on Horses?

Ergots are similar to chestnuts in that they are hard callouses protruding from the skin on horses. Ergots are found on the underside of the fetlock joint, and are smaller in diameter than chestnuts. Ergots are pointy, similar to the eraser at the end of a wooden pencil. Ergots are thought to be a mechanism aimed to help guide water away from the heel of a horse’s foot. Hooves that stay too wet can become a breeding ground for various conditions including thrush, white line disease, hoof abscesses, and cracks.

What Is the Difference Between a Chestnut and an Ergot?

Chestnuts and ergots are very similar in how they evolved and what they are made of. They are both made of keratinized skin cells. While chestnuts are likely remnants of a carpal paw pad, ergots are likely leftover from a similar evolutionary process relating to a toe or dewclaw. The main difference between the two is location. Chestnuts are always found on the back of the forelimb in the region of the carpus or “knee.” Ergots are found at the back of the fetlock.

How Do You Get Rid of Chestnuts and Ergots on a Horse?

You never want to completely get rid of a horse’s chestnut or ergot. They are a normal part of a horse’s body, and it can be very painful to remove them at the skin level. Some chestnuts or ergots will not shed their outer layer properly and can become very large. Improperly shed chestnuts/ergots can cause skin problems due to an increased risk of them catching on things and being torn off. In these cases, a hoof knife or rasp can be used to trim down the excess tissue. Ask your veterinarian or farrier for assistance if you are uncomfortable deciding how far back to trim them.

Featured Image:


Lusi, Carla M., Helen M.S. Davies. The Connectivity and Histological Structure of the Equine Ergot—a Preliminary Study. Journal of Equine Veterinary Science, vol. 51, pp. 79–85. 2017.


Kaela Schraer, DVM


Kaela Schraer, DVM


Dr. Kaela Schraer graduated from Tufts Cummings School of Veterinary Medicine in 2017 with her doctorate in veterinary medicine. After...

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