Dimethyl sulfoxide (DMSO) is a byproduct of the production of a chemical solvent. It is a clear, colorless liquid that mixes readily with most organic compounds. It will form crystals in the presence of strong acids.

DMSO is rapidly absorbed across intact epithelium (skin), by oral or intravenous routes. Interestingly, its first medical use was as a preservative for various types of tissues and body fluids including blood, blood cells, bone marrow, sperm, and cornea (eye) grafts.

Most of a dose of DMSO is eliminated in the urine and the drug itself causes a transient increase in urine production. Small amounts are also released via the lungs, resulting in a peculiar odor to the breath that has a rather unique quality and has been described as anything from sweetish to garlic-like.

Dosage and route administration
DMSO medical grade is supplied as a 90 percent solution of DMSO with 10 percent water.

DMSO is most frequently used to treat muscular, tendinous, or joint sprains and strains, and/or to carry other medications, such as corticosteroids, into such injured areas. Interestingly, many research studies have failed to demonstrate any anti-inflammatory or analgesic (pain-relieving) effect for DMSO. Clinical experience with the drug, however, clearly indicates otherwise. Some experimental studies have shown DMSO to be beneficial in reducing edema, countering inflammation, and encouraging wound healing when the DMSO was applied to an area of the body at some distance from the injured area.

DMSO is a very effective carrier of a variety of medications and will allow these drugs to cross intact skin. Medications that will be carried across skin by DMSO include antibiotics, antifungal drugs, corticosteroids, and dyes. The DMSO, and the absorbed drugs, are then distributed throughout the body, but remain at a higher concentration at the skin location where they were applied.

In addition to carrying antibiotics and antifungal drugs into the tissues, DMSO is active against bacteria and fungi on its own. DMSO has the ability both to inhibit the growth of and actually kill several bacterial species, such as Streptococcus, Staphylococcus, Corynebacterium, E. coli, and Proteus-all common wound invaders. DMSO is also effective in inhibiting the growth of (although not actually killing) the common fungal species that cause skin infections.

It has also been used experimentally by some veterinarians in attempts to decrease the edema associated with trauma to or infections of the brain or spinal cord. It is not clear whether intravenous administration of DMSO would have any benefit over application to the skin. Research in some animal species shows no difference in elimination times for the two routes while in others the intravenous dose is eliminated much quicker than the cutaneous (skin) applications.

Special Precautions
DMSO should be applied wearing rubber gloves to prevent human absorption and possible side effects. The area being treated should be thoroughly washed and dried prior to application of DMSO, to avoid carrying un\wanted drugs or other substances through the skin. In particular, any liniments or rubs, particularly iodine or mercury compounds, should be removed thoroughly. DMSO will carry these through the skin and cause a severe inflammatory reaction.

Side Effects (toxicity)
DMSO causes a local inflammatory’ response, mediated largely by a release of histamine from the skin in the area \V here it is applied. This will cause generation of heat at the site as well as other reactions which will vary from a mild swelling of the skin to actual blistering. Drying and “scurf” dry, dead skin formation is common with this and all solvents when applied to the skin. The degree of a local reaction appears to be related to individual sensitivity, the degree of inflammation already present (usually’ worse \when applied to acutely inflamed areas, and whether or not the area is bandaged after application of DMS0 (worse under a bandage). This reaction will abate and eventually disappear after several days, when the skin cells that release histamine (“mast” cells) have been depleted.

Associated with the inflammatory reaction to DMSO is some degree of pain/irritation that will cause the horse to react. Some violently resist application of DMSO, while others show only a short-lived mild reaction such as stamping their feet.

A wide variety of experimental animals show ocular (eye) changes when exposed to DMSO for prolonged periods. Typically, there are changes in the lens that make them “near-sighted.” These changes appear to be reversible to some degree after DMSO is stopped. There is no data available on the horse.

Drug Interactions
DMSO should not be used within a few days of administration of cholinesterase-inhibiting pesticides or worming preparations organophosphates!

Pregnancy – Nursing
DMSO has been clearly shown to cause birth defects and is contraindicated in pregnancy.
DMSO should not be used in breeding animals.

Drug Testing
Detection Time Information: DMSO’s pharmacological effects are not thought of as lasting longer than about 8 hours after a clinical dose, particularly an IV dose. DMSO and its metabolites are natural substances found in all horses. The recommended international threshold for DMSO is 15 mcg/ml in urine and 1 mcg/ml in plasma.

Canadian authorities report a 36-hour detection time, Australian authorities, 72 hours after oral administration.

Horseman’s Comments


One should scrub the leg of the horse from previously applied liniments and medications before applying DMSO. This product could cause severe irritation of the skin when mixed with some other products and topical medications, even with small traces of them.

Dimethyl sulfoxide (DMSO), a by-product of the wood industry, has been in use as a commercial solvent since 1953. It is also one of the most studied but least understood pharmaceutical agents of our time–at least in the United States
Though this product is actually an industrial solvent it has been used around horses several decades. It is often prescribed and recommended by many veterinarians. The use of this product is known mainly as a topical application in curing various sprains, sore muscles, ligaments or tendons on horses and even on people. DMSO is also used for direct injecting the horse. This latter use is less known to the public and I would not recommend to anyone to use this product in that fashion without consulting a veterinarian.

DMSO can be often mixed with other drugs for topical use. This product has immense penetrating qualities and when mixed with other drugs it will help them to penetrate deeper when applied as a topical treatment. I often mix this product with liquid furazone to reduce possible “scurfing” when using straight for longer period of time. It is very handy product for medical purposes.

It is recommended that you use either rubber gloves or a “paint brush” when using this product.

DMSO comes in a gel (fig. 1) or a liquid form.