MSM, or methylsulfonylmethane, is a small sulphur compound found in many joint and coat products for dogs, often alongside glucosamine, chondroitin or collagen. We found only one study in dogs that tests MSM on its own. It looked at the coat of 32 poodles, not at their joints, and found no change. In people with knee osteoarthritis the measured improvements are small. It does seem to be well tolerated.
What MSM is and where it comes from
MSM is also sold as dimethyl sulfone or, on some labels, as organic sulphur. The molecule forms naturally in the sulphur cycle and is present in fruit, vegetables, cereals, coffee, tea and cow's milk, although in minute amounts, in the order of hundredths of a part per million. Commercial MSM is made by oxidising dimethyl sulfoxide (DMSO) with hydrogen peroxide and then purifying it, and a 2017 review of its uses and safety describes it as chemically identical to the natural compound.
The usual sales pitch is that it supplies sulphur for cartilage, collagen or the keratin in hair. That has not been shown. The same review explains that its role as a sulphur donor is still being studied, and that in people, taking more MSM has not been seen to raise blood sulphate in proportion. The Merck Veterinary Manual lists MSM among the products used for osteoarthritis pain in pets, and cautions that most of these products have not been scientifically tested in animals.
Studies in dogs and in people
In dogs
The coat study, published in 2024, split its 32 poodles into four groups of 8 for 65 days: standard food, food with 0.2% MSM, food with 0.2% myo-inositol (a different substance), or food with both. Observers who did not know what each dog was eating scored the coats and found no differences between groups. Under the microscope, the scales on the hair were thinner than in the control group in the two groups given myo-inositol, but not in the group given MSM alone. The authors conclude that MSM and myo-inositol improve the coat, though the results from the MSM-only group do not support that part of the conclusion.
For joints, MSM has been tested in dogs only in mixtures, such as the chew, also containing glucosamine, chondroitin and avocado and soya extract, that 16 dogs with hip osteoarthritis took for 6 weeks in the trial by Kampa and colleagues (2023). Their weight-bearing on the leg did not improve significantly, unlike in the carprofen and marine extract groups. In the 2022 systematic review of osteoarthritis products for dogs and cats, one of the two combination products that did show an effect contained MSM, in a mix too crowded for its share to show: several plants, omega-3, glucosamine and chondroitin, glutamine and hyaluronic acid.
In people with knee osteoarthritis
The human trials are few and small, though mostly favourable:
- A 2006 pilot trial gave 50 adults aged 40 to 76 either 3 g of MSM twice a day or a placebo for 12 weeks. The MSM group had less pain and less physical limitation on the WOMAC scale, with no major adverse effects.
- A 2011 trial with 49 people aged 45 to 90 found that 1.125 g three times a day for 12 weeks improved physical function and the total score. The authors point out that the improvements were small and that it is not yet known whether they matter clinically.
- In a 2023 Japanese trial with 88 healthy adults who had mild knee pain, 2 g a day for 12 weeks improved scores on a knee quality-of-life questionnaire compared with placebo, by a narrow margin (p = 0.046).
A 2011 meta-analysis pooled three good-quality trials, two with DMSO and one with MSM (326 patients). Pain fell by 6.34 mm on a visual scale, which was not statistically significant. Its authors conclude that on these data neither compound relieves pain to a clinically relevant degree, although the results were too mixed to settle the question.
How much MSM the studies used
There is no established MSM dose for dogs, and human doses do not translate directly.
| Study | Who | Amount | Duration |
|---|---|---|---|
| Poodles, 2024 | 32 adult poodles | 0.2% of the food ration | 65 days |
| Kampa, 2023 | 16 dogs with osteoarthritis | 800 mg of MSM for every 900 mg of glucosamine, dosed at 30 mg of glucosamine per kg: about 27 mg of MSM per kg a day (our calculation; the study does not give this figure) | 6 weeks |
| Pilot trial, 2006 | 50 people | 6 g a day | 12 weeks |
| 2011 trial | 49 people | 1.125 g three times a day (3.375 g) | 12 weeks |
| Japanese trial, 2023 | 88 people | 2 g a day | 12 weeks |
Safety and interactions
In the poodle study, weight, food intake and stools stayed normal in every group for the full 65 days. In people, the 2017 review describes MSM as well tolerated up to about 4 g a day, with few side effects, all of them mild. Laboratory rats given 1.5 g per kg a day for 90 days had no observed adverse effects, and 1 g per kg a day caused none in pregnant rats either. For dogs, we found no established toxic dose, no studies in pregnant or lactating bitches or in puppies, and no safety data in dogs with kidney, liver or other chronic disease, so giving it to a dog with a chronic illness is the vet's call.
If the product is a mixture, check it with the vet before you start. MSM usually comes with glucosamine, chondroitin or collagen, and the precautions for those ingredients matter more than those for MSM; the ones for glucosamine (shellfish, diabetes, anticoagulants) are in the article on glucosamine and chondroitin. Check with the vet too if your dog is pregnant, lactating or a puppy, has a chronic illness or takes daily medication.
A 2023 laboratory study using human liver enzymes found that MSM, glucosamine and chondroitin did not inhibit any of seven enzymes that clear many drugs from the body, so interference with medicines by that route is unlikely. The work was done in test tubes rather than in dogs, and the same authors urge caution with glucosamine because interaction cases have already been reported.
Sources
- Methylsulfonylmethane: Applications and Safety of a Novel Dietary Supplement. Nutrients, 2017.
- Nondrug Therapies Used to Relieve Pain in Animals. Merck Veterinary Manual, 2025.
- Dietary Supplementation with Methylsulfonylmethane and Myo-Inositol Supports Hair Quality and Fecal Microbiome in Poodles. Animals, 2024.
- Study of the effectiveness of glucosamine and chondroitin sulfate, marine based fatty acid compounds (PCSO-524 and EAB-277), and carprofen for the treatment of dogs with hip osteoarthritis. Frontiers in Veterinary Science, 2023.
- A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis. International Journal of Molecular Sciences, 2022.
- Efficacy of methylsulfonylmethane (MSM) in osteoarthritis pain of the knee: a pilot clinical trial. Osteoarthritis and Cartilage, 2006.
- Efficacy of methylsulfonylmethane supplementation on osteoarthritis of the knee: a randomized controlled study. BMC Complementary and Alternative Medicine, 2011.
- Methylsulfonylmethane Improves Knee Quality of Life in Participants with Mild Knee Pain: A Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients, 2023.
- Meta-analysis of the related nutritional supplements dimethyl sulfoxide and methylsulfonylmethane in the treatment of osteoarthritis of the knee. Evidence-Based Complementary and Alternative Medicine, 2011.
- Investigation of Drug-Interaction Potential for Arthritis Dietary Supplements: Chondroitin Sulfate, Glucosamine, and Methylsulfonylmethane. Molecules, 2023.