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methuhl-suhl-FAHN-uhl-methayn - Pronunciation guide

Brand Names

  • Chondro-Flex
  • Cosequin
  • Equinyl
  • Glyco-Flex
  • MSM
  • Next Level
  • PureForm
  • SmartFlex


Methylsulfonylmethane, generally referred to as MSM, is a natural sulfur-containing compound that can be found in your horse's body as well as in fruits, vegetables and fresh forage and grains. Your horse uses this supplemental sulfur primarily as a source of sulfur. It is important for healthy cartilage and antioxidant actions. In your horse's body, the compound splits into methionine and cysteine, two important amino acids.

Sulfur is important for connective tissue health. It is a component of glucosamine and collagen. Sulfur is also important for keratin, which is found in hair, skin and hooves. Sulfur aids in cell membrane health and communication between cells, including nerve cells. It helps with carbohydrate metabolism via insulin. Sulfur can help protect cells against damage from radiation via its antioxidant activity and can help chelate or bind harmful heavy metals.

The supplement MSM is derived from DMSO or dimethylsulfoxide. DMSO is widely used in the horse industry to fight inflammation. MSM has multiple uses for horses. It is primarily thought of as an arthritis supplement and pain medication but has other actions as well. Boosting the immune system is also considered to be a benefit of MSM supplementation. The main actions of MSM for horses are to reduce inflammation and improve circulation.


Methylsulfonylmethane is primarily given to horses as a joint supplement to aid in the health of collagen and cartilage. As noted above, MSM has many other potentially helpful actions for an individual horse. Skin, coat and hoof supplements often contain added MSM for the sulfur. It may benefit a horse healing from an injury or suffering from chronic arthritic changes in its joints.

Anecdotally, MSM has been helpful for horses with Equine Protozoal Myelitis (EPM), back problems and epiphysitis, which is an inflammation of the growth centers in the joints of young horses. Allergies and gastrointestinal upsets are also sometimes aided by this supplement.

Dosage and Administration

Because of the wide variety of products that incorporate methysulfonylmethane as an active ingredient, it is difficult to provide a generic dosage and administration table. Please refer to the package insert of the product for instructions concerning dosage and administration.

Side Effects

There are no known side effects listed for methylsulfonylmethane, but the compound can be found in both dietary and industrial grades. Horses should only be fed dietary grade MSM.


Methylsulfonylmethane has not been approved for use in pregnant mares or in horses intended for breeding. It should also not be given to horses headed for slaughter and intended for human consumption. MSM is prohibited for use in ruminants, so any goats acting as stable mascots should not be fed any MSM supplements.


Due to its many actions in the body, methylsulfonylmethane should be used with care in certain horses. Any horses with clotting disorders or taking medications to aid in clotting should not receive this supplement without close veterinary supervision. Diabetic equines or horses with any condition causing increased blood glucose (hyperglycemia) should not take MSM. The same is true of any horses with a history of urinary tract stones or horses with known allergies to shellfish or shellfish components.


There are no studies indicating any toxicity from the use of methylsulfonylmethane in a variety of species. If an individual horse were to consume way above the daily recommended dose, it would be advisable to contact your veterinarian for observation.


About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.