DMSO safety -

[Clean your hands and the area to be treated
Wash your hands and under your nails thoroughly before using topical DMSO. You should always clean the area for which you plan a DMSO use, just in case there is some harmful substance on your skin with a molecule small enough to go through. Note that only those substances that could penetrate by themselves if left on the skin long enough can be transported through (more quickly) by dimethyl sulfoxide. Bacteria and viruses are too large and thus are not able to pass through, and bacteria cannot grow in dimethyl sulfoxide of 25 percent strength or more.]
DMSO Uses. Benefits of Dimethyl Sulfoxide