Ummm...
I don't want to alarm you too much, but this is something you really should talk to your doctor about.
DMSO does, indeed, carry pretty much anything through the skin, including any dirt/dust on the skin. It's an amazing substance because of this.
It is considered a carcinogenic substance, either due to its own properties or due to the fact that it carries little bits of dirt into your body.
My information is around ten years old, from when my wife was in bio-chemistry, but I doubt that the chemical will have changed.
I'm guessing that the reason that it's mostly used on horses is because of the potential danger of DMSO.
I did a quick search, and found the
MSDS for the stuff. It's not considered horribly toxic, but the MSDS (material safety data sheet, the industry standard that explains information about the chemical, including cleanup, contact, etc...) does call it "harmful" and does not cover the carcinogenic properties.
Be very, very careful with what you put on your wrist prior to treatment. I would scrub with a freshly cleaned washcloth and no soap, just water as hot as you can stand. Dry the arm, let the rest of it evaporate, then put the stuff on.