This article was reviewed and updated April 5, 2023.

Horse smegma is not a topic that gets a lot of press.

I went on a mission in 2013 to find the definitive study on smegma and laminitis and came up empty. None seemed to exist.

Horse smegma is the stuff that builds up inside the male horse’s sheath.

I found a few desperate forum postings by horse owners requesting help in dealing with horses with an itchy sheath, as well as references on less established sites to excessive smegma production in horses with insulin resistance. But I didn’t find one university or medical site that had waded into the conversation, as of 2013.

Kurt has what I would describe as excess smegma. And he used to itch a lot. He was backing into me, sometimes at a trot. Sometimes, he would see me come out of the house and run to me from across the driveway, then spin around and back into me.

My vet made a renewed effort to tackle this issue in February 2013 when I pointed out the problem had existed for five years, and I felt like a terrible owner.

Luckily, I now have a female vet. My previous male vets just sort of sighed when I brought up the topic. I think their take on it was that Kurt should take a little itch like a man. It wasn’t a “little” itch, and Kurt preferred to fix it.

In the past, the female vet tried cleaning Kurt herself, as well as approving the idea of me trying various feminine hygiene products on Kurt. None worked.

Kurt’s biggest tumor in his sheath on Feb. 17, 2013.

This time, she suggested we put Kurt on Tagamet, or cimetidine, commonly used as an antacid in horses and people because it blocks the action of histamine on certain cells in the stomach. Maybe it would block a similar allergic reaction in the sheath. The drug also has been shown in some studies to benefit cancer patients. Kurt has several tumors in his sheath. The idea was to reduce the itching and shrink the tumors.

Note that my own search of these tumor studies found more research that says the drug doesn’t help than does. However, there are a lot of forums with horse owners reporting that Tagamet prevented regrowth of a tumor that was removed. I would consider inhibiting growth of tumors worth using it. Mostly, I cared about the itching.

Kurt started taking the Tagamet on March 5, 2013, and he was on it for a month. 

The experiment looked good in the early going. He didn’t back into me very much. We went days without him bothering me. I think he was distracted by the snow. Once the weather warmed to 70 degrees, Kurt became itchy again. I’m not recommending Tagamet as a treatment for the itch. We stopped using it.

After hearing some local radio broadcasters rave about a mixture of water, mouthwash and vinegar as a foot wash, I decided to try that on Kurt’s sheath. It turned out to be a great concoction for cleaning a sheath, and I added baking soda to the mix because I thought it helped reduce the itch even more. Kurt became much less frantic. And the cleanings reduced the smell considerably.

I later removed the vinegar from the mixture because I didn’t think it was needed.

I clean Kurt every two weeks in a process that I describe here.

Silvia Kornherr, an equine nutritionist from Canada, read my original post on this topic and commented that insulin resistance and Cushing’s disease deal with metabolic dysfunction, which leads to many hormonal imbalances, not just inbalances in insulin and ACTH. Logically, there are going to be secondary changes in many areas affected by the hormonal imbalances.

She said many owners of horses with Cushing’s report increased smegma production and a change in the consistency of the smegma. The smegma becomes very thick, glue-like and abrasive against the sensitive sheath skin, causing inflammation, itching and infection, as well as blockage.

Based on her experience in treating horses with this problem, she suggested I try Animal Legends’ Tea Tree Oil enriched with vitamins A, D and E in the spray formulation. So we did in July 2013. We don’t use it currently because the washing alone seems to solve the problem.

So what is the contents of smegma?

There’s an amusing article on ScienceBlogs that discusses the content. The article says smegma is a waxy, oily secretion from skin cells. It consists of about 71 percent fatty acids and 18 percent cholesterol and cholesterol esters.

The article looks at a study published in 1947 by top research institutions that applied horse smegma to mice (poor mice) to see if the smegma produced cancerous tumors. It did not.

I’m not trying to blame Kurt’s tumors on the smegma. The mice study did say that horse smegma was used because penile cancer is frequent in the horse. But, technically, Kurt has sheath tumors. And that study was done in 1947. There are other statements in the study that are not backed up by current science.

Another interesting study is one published by a veterinary school in Turkey in 2006 that looked at the immune function of the reproductive tract of stallions, including their sheaths, and it concluded that the reproductive tract does likely “contribute to the immune surveillance” of the horse. I suspect the fact that Kurt’s sheath has been having an immune system reaction is not helping the insulin resistance.

I hit the jackpot when I did a Google search of “diabetes” and “itch,” because Google suggested several additional terms and one was “groin.” A forum on the site of the American Diabetes Association is full of people, both male and female, with anguished stories about groin itch related to their diabetes. And the ADA’s page on skin disorders says: “As many as 33 percent of people with diabetes will have a skin disorder caused or affected by diabetes at some time in their lives. In fact, such problems are sometimes the first sign that a person has diabetes. … These include bacterial infections, fungal infections, and itching.”

If your laminitic horse has jock itch, and your vet rolls his eyes or sighs, this is one condition that you can help on your own with products found easily. Click this link to read a tutorial on cleaning an itchy sheath. Your horse will thank you.