From the Manufacturer:
MSM (methylsulfonylmethane), a metabolite of DMSO (dimethylsulfoxide), is a naturally occurring component of every living cell. MSM is a bioavailable form of sulfur, which is necessary for the proper function of the body's skin, hair, nails, connective tissue, amino acid production, immune system, and healthy joints. Sulfur is considered a macronutrient and must be consumed each day for healthy function and growth of the body.