Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula (CH3)2SO. It can uniquely provide solubility to certain very polar small molecules, such as simple biomolecules with multiple protic functional groups.

DMSO is widely used as a topical analgesic and anti-inflammatory, and is a known antioxidant. It can quickly penetrate the skin and other membranes without damaging them. 

DMSO has the unusual ability to depress the freezing point of water dramatically, while maintaining viability with many cell and tissue types. It is a sulfur-containing organic compound that is derived from MSM, and can be used internally or externally.