Absolutely. I used it for a couple of months as a sort of experiment (prescribed, not self-medication) during rehab after an illness in 2011. The nurses were scared of it--they wore gloves when they brought it to me, and when I was unable to apply it myself, they were careful to avoid ALL contact with the gel as they rubbed it on. My primary care doc didn't think it was worth the risk of side effects and took me off it as soon as I got out of the hospital. FWIW, I didn't notice any effects at all, either side or therapeutic, but I was pretty much out of it for several weeks.