DMSO is a clear odorless liquid, inexpensively produced as a by-product of the paper industry. It is widely available in the USA as a solvent but its medical use is currently restricted by the FDA to the palliative treatment of interstitial cystitis and to certain experimental applications. DMSO is used topically to decrease pain and speed the healing of wounds, burns, and muscle and skeletal injuries. DMSO is also used topically to treat painful conditions such as headache, inflammation, osteoarthritis, rheumatoid arthritis, and severe facial pain called tic douloureux.