An alkyl sulfoxide that is practically odourless in its purified form. As a highly polar organic liquid, it is a powerful solvent. Its biologic activities include the ability to penetrate plant and animal tissues and to preserve living cells during freezing. It has been used investigationally as a topical analgesic and anti-inflammatory agent, and as an agent to increase the penetrability of other substances. It is available as a 50 percent solution for direct instillation into the bladder for treatment of interstitial cystitis.