The Head Scratcher That Is DMSO

DMSO is the much quicker and easier way to say, “Dimethyl sulfoxide.”

About that, pretty much everyone agrees. It goes downhill from there.

Although it was first synthesized way back in 1866 by a Russian scientist, DMSO first started being touted in medicine in the 1960s. I remember first hearing about DMSO in the 1970s. In fact, I remember hearing about it on a 60 Minutes program, on a Sunday evening.  Here’s the introduction, featuring the late, great Mike Wallace.

Quick aside: This whole DMSO thing had a bit of a culty feel to it. There were charges about the “medical establishment” keeping DMSO under wraps, of wanting to suppress a miracle cure, and that sort of thing. That was about 50 years ago, and now you can pick it up at tack stores. In what may not come as a great surprise, Jacob Lab still sells the stuff, too. (Dr. Jacob passed away in 2015, at the age of 91.)

I recall being swept up in all of this enthusiasm. In fact, as a student, I—apparently much less worried about nuances such as science and proof—was fairly certain that all of my teachers in veterinary school had missed the boat when it came to treating tendon injuries in horses. All I thought you had to do was rub DMSO on them, and, “poof,” the inflammation in the tendon would be gone and the tendon would be better. Naivete is a wonderful thing when it comes to promoting therapies.

What is DMSO?

DMSO (dimethyl sulfoxide, which is also the last time that I am going to type this out) comes from a substance found in wood. It’s a by-product of paper making.

DMSO is an organic compound—that is, it contains carbon—that also contains sulfur. It’s colorless, but definitely not odorless. It’s been used as a solvent since the mid-19th century, and it can dissolve many other substances: in the case of DMSO, a whole lot of other substances, such as herbicides, fungicides, plant hormones, and even some antibiotics. It also mixes well with many other substances, which is one reason why it gets mixed into so many substances.

What is DMSO supposed to do?

Two things, mostly. First, since sometime in the mid-20th century, researchers have explored its use as an anti-inflammatory agent. It’s also sometimes used to try to increase the body’s absorption of other medications. Which means:

1. People slap the stuff into or onto horses that have any condition of which inflammation can be a component (which are many), and,
2. People frequently mix the stuff with other medications in hopes that you can get more medicine into the horse, particularly when those medicines are applied to the skin.

What’s DMSO used for (as a medicine)?

In humans, where a certain amount of proof has to be obtained before medications get approved (go figure), the United States Food and Drug Administration (FDA) has approved DMSO as a prescription medication only for treating the symptoms of painful bladder syndrome, which sounds just awful. To my knowledge, horses don’t get it, but then again, I’m not sure how we’d know. But I digress.

In horses, where standards of proof aren’t really much of a thing, DMSO can be given for or added to just about anything, it seems. I attended a talk at an American Association of Equine Practitioners convention a couple of decades back on DMSO, where the author found 31 conditions for which DMSO had been advocated. So if your horse has pleuropneumonia or laminitis or neurologic trauma or cancer or joint inflammation or a uterine infection or a splint or a healing wound or a bowed tendon or an eye condition or just-about-any-sort-of-swelling or—well, you get the idea—you may be able to find a treatment scheme that advocates the use of DMSO.

Does it work?

That’s harder to say.

A quick aside: As with discussions of any sort of treatment, it’s really a good idea to try not to ask the “work” question in the first place. You should try to be more specific. So, for example, you could ask, “Does DMSO affect the clinical outcome in horses with laminitis,” or that sort of thing. “Work” is just too general a term, although it certainly is used all of the time.

You can definitely find studies supporting one or both of the activities for which DMSO is advocated. That is, there have been studies showing that DMSO is anti-inflammatory, and studies showing that it helps other medicines (for example, corticosteroids) get through the skin. Many of those studies are in laboratory conditions.

Unfortunately, in living organisms such as the horse, most of those activities haven’t been shown to either 1) Happen, or 2) Really matter much, when it comes to treatment outcomes.

Here’s an example of the problems, when it comes to answering the “work” question in a larger context. Let’s take osteoarthritis. DMSO cream or gel is commonly rubbed onto arthritic joints. However, a 2011 analysis of studies on the use of DMSO to relieve the pain of osteoarthritis found that it didn’t work any better than a placebo (and it had the same conclusions for MSM—a DMSO derivative—too).

In horses, evidence for the effectiveness of DMSO is even harder to find. It hasn’t been shown to help in endotoxemia (which is something that you never want your horse to have). It seemed to help experimentally induced joint inflammation in horses – but your horse will never get inflammation using the experimental model.

From a “helping medicines penetrate” standpoint, there’s perhaps a bit more evidence. For example, DMSO is commonly added to an antifungal medication for the treatments of fungal infections of horse eyes. Of course, fungal infections of the horse’s eye are a serious condition, and you’d never, ever want to try to treat them yourself. That’s a job for your veterinarian, or a veterinary ophthalmologist. It’s been shown to help medications get into arthritic joints in people – but not horses – and in that same study, DMSO by itself didn’t work any better than a placebo.

Nevertheless, countless preparations are made for the treatment of horses that include DMSO, in hopes that it will make the treatment get into the horse better. Whether they do or not, well, that’s another question.

How about a dose?

Oh, that. There don’t seem to be any studies that show how one determines the proper dose of DMSO. You can buy concentrations of DMSO from10% to 90%. You can rub it on daily. Or twice a day. Or more often. Who knows? It’s the same for oral or intravenous administration, too. The dose is guided by whatever criteria the person who is dosing uses. That’s not exactly a ringing endorsement of any sort of therapy.

But is it at least safe?

Happily, considering how widely DMSO may be used in some therapeutic circles, DMSO seems to be pretty safe. That is, you’re not likely to kill your horse with the stuff. But there are some caveats and concerns.

There’s such a thing as industrial grade DMSO, since it’s used for many industrial uses. Industrial grade DMSO may contain a number of impurities. Since DMSO can help some medications penetrate the skin, there’s the possibility that it could help the impurities penetrate, too.

If you keep rubbing DMSO into your horse’s skin, there’s a chance he could get very upset with you after a bit. That’s because DMSO can irritate the skin. Horses demonstrate their displeasure in a number of ways, such as trying to kick the person who is creating it. So be careful if you’re going to rub DMSO onto your horse for a period of time.

Given intravenously or orally, DMSO puts a noticeable smell in the air. Some describe it as garlic-like, although, as a garlic lover, I find that description both insulting and inaccurate. I think it’s more accurate to just say that it stinks.

Another aside: A couple of decades back, I walked into a barn full of horses that had all been given intravenous DMSO. The idea was that since they had just shown, they must all have inflammation, so they all got DMSO to, um, take care of the inflammation (I guess). I have no idea if it helped—it didn’t kill any of the horses—but mostly I remember the urgency with which I felt I needed to get out of the barn. PHEW!

Another concern has to do with the solvent properties of DMSO. If you put in on your horse’s skin, it can theoretically cause anything on the skin to be absorbed. I’m not sure how real this concern is—I’ve never heard of any adverse effects in horses—but why not wash your horse’s skin before putting it on, just to be on the safe side?

Where can you get it?

Oh, just about anywhere, it seems. While it used to be hard to come by, you can get DMSO without a prescription, as a gel, as a cream, from a health food store, tack shop, or over the internet. Getting DMSO is the easy part. What you’re going to get, well, that’s another question.

Bottom line?

The bottom line is that from a therapeutic standpoint, DMSO is really a head scratcher. It seems to be something of a therapy in search of a condition to treat: and remember, this is after something like 60 years of research. There are certainly lots of conditions to treat—just very few of them for which DMSO has actually been shown to do anything. Usually, when something has been investigated for such a long time, treatment effects start to become obvious. With DMSO, not so much.

Hold your nose.

This article originally appeared on DoctorRamey.com and is reprinted here with permission.

About the Author

Dr. David Ramey is a 1983 graduate of the Colorado State University School of Veterinary Medicine. In addition to being a full-time equine veterinary practitioner in Encino, California, Dr. Ramey is also an internationally recognized author, lecturer and blogger. Dr. Ramey is a vocal advocate for the application of science to medicine, and—as such—for the welfare of the