How does dimethyl sulfoxide transport other molecules through skin?
DMSO interacts with the outer membrane of skin, the stratum corneum.  The stratum corneum is a typical lipid bilayer and DMSO can solvate the exposed hydrophilic lipid head.  This results in a weakening of the lateral forces between the individual phospholipid molecules.  The weakened lateral forces result in a widening of the channel between the phospholipid molecules and the widened channel allows small molecules to pass through the lipid layer.  After the DMSO is removed the lipid bilayer restores itself back to normal.



Although it is agreed that small molecules can pass through the DMSO-affected bilayer, there is some evidence that larger molecules such as viral agents might also pass through.  There is also some controversy over the effect of DMSO on the blood-brain barrier.  Here is a link to a nice review of DMSO's pharmacological effects, including transport of larger molecules and transport across the blood-brain barrier.