DMSO, or dimethyl sulfoxide, is a by-product of paper making. It comes from a substance found in wood. DMSO has been used as an industrial solvent since the mid-1800s. From about the mid-20th century, researchers have explored its use as an anti-inflammatory agent. The FDA has approved DMSO as a prescription medication for treating symptoms of painful bladder syndrome. It's also used under medical supervision to treat several other conditions, including shingles. DMSO is easily absorbed by the skin. It's sometimes used to increase the body's absorption of other medications. DMSO is available without a prescription most often in gel or cream form. It can be purchased in health food stores, by mail order, and on the Internet. While it can sometimes be found as an oral supplement, its safety is unclear. DMSO is primarily used by applying it to the skin.