MSM started out as a joint supplement and has quietly moved into the hair and skin aisle. The pitch is that it supplies sulfur, and sulfur is part of what makes hair strong. The chemistry behind that is sound. The human research to back it up has not been done.
The short answer
MSM is a sulfur compound, and sulfur is genuinely part of keratin, the protein your hair and nails are made from. That gives the idea a real basis. What is missing is evidence in people. The hair research is mostly laboratory work, animal studies, and reasoning from the mechanism, with no good human trial showing that taking MSM grows hair or strengthens nails. It is well tolerated and considered safe at up to 4 grams a day, so the risk is low, and so is the proof.
What MSM is
MSM stands for methylsulfonylmethane. It is a sulfur-containing compound that occurs naturally in small amounts in foods like tomatoes, corn, and milk, though it breaks down easily with heat and processing, so the amounts you get from food are tiny. Supplements use a lab-made version.
Sulfur is the third most abundant mineral in your body and part of the structure of connective tissue, skin, and hair. MSM is sold as a way to supply it in a form your body can use easily.
Why the hair claim sounds convincing
Keratin, the protein in hair and nails, is held together by bonds formed from an amino acid called cysteine, and cysteine contains sulfur. Those sulfur bonds are what make hair strong and resistant to damage.
The reasoning follows from there. More available sulfur should mean better keratin, and better keratin should mean stronger hair. It is the same shape of argument used for collagen, silica, and most other structural beauty supplements, and it shares the same weakness. Supplying a building block does not automatically mean your body builds more of the finished structure.
What the research actually shows
Here is where the case thins out.
The study most often cited for MSM and hair was done in mice, and it tested MSM applied to the skin alongside another compound rather than taken as a supplement. Other supportive work comes from animals too, including studies on hair quality in kittens and dogs. Those results are interesting, and they are not evidence about people taking a capsule.
For humans, MSM has been studied more seriously for joint pain and for skin quality, with some small trials. For hair specifically, the evidence stays mechanistic. Reviews of MSM describe the hair evidence as based on how it works in theory rather than on clinical results, and that is a fair summary. No trial has measured hair growth or thickness in people taking oral MSM against a placebo.
Dose and safety
MSM has a good safety record, which is the strongest thing about it. It is recognised as safe at doses up to 4 grams a day, and most studies use somewhere between 1.5 and 3 grams. Side effects tend to be mild, with stomach upset the most common complaint, and taking it with food helps.
So the risk of trying it is low. That is different from a reason to expect results.
The bottom line
MSM has a plausible mechanism, a clean safety record, and no human evidence for hair, skin, or nails. Sulfur really is part of keratin, and MSM really does supply sulfur, but nobody has shown that taking it changes how your hair or nails behave. If you already take it for joints and wonder whether your hair benefits too, there is no harm in finding out. If you are buying it specifically for hair growth, you are paying for a theory. The ingredients with actual human trials behind them are covered in our guides on hair growth supplements and which supplements help your skin.
Questions people ask
Does MSM help hair growth?
There is no human trial showing that it does. The supporting evidence comes from animal studies and from how sulfur works in keratin, which is reasoning rather than proof.
How much MSM should I take?
Studies use roughly 1.5 to 3 grams a day, and up to 4 grams is considered safe. Since the hair evidence is missing, there is no established dose for that purpose.
Is MSM safe?
It has a good safety record and is well tolerated at up to 4 grams a day. Mild stomach upset is the most common side effect, and taking it with food helps.
Is MSM the same as sulfur?
MSM is a compound that contains sulfur and delivers it in a form your body can use. Sulfur itself is a mineral your body needs for connective tissue, skin, and hair.
References
National Institutes of Health, Office of Dietary Supplements. Dietary Supplements for Exercise and Athletic Performance (methylsulfonylmethane section). https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/
Butawan M, Benjamin RL, Bloomer RJ. Methylsulfonylmethane: Applications and Safety of a Novel Dietary Supplement. Nutrients. 2017;9(3):290. https://pmc.ncbi.nlm.nih.gov/articles/PMC5372953/
This article is for information only and is not medical advice. Supplements are not meant to diagnose, treat, cure, or prevent any illness. Talk to your doctor before starting anything new, especially if you are pregnant, breastfeeding, or taking medication.
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