I do not subscribe to the dilute above the waist and not below stuff. I use DMSO on my knees regularly and always put on a thin layer of castor oil first. This helps with protecting my skin AND from half the DMSO being soaked up by the skin in my hand on the way to my knees! DMSO is a solvent and it wants IN! The one time I forgot the castor oil and used the stuff straight, and the skin on my kneecaps was red and scaly. I threw every healing oil I have at it, and the stuff that worked overnight was av-ee-no lotion. Please so not use DMSO straight unless you're diluting, and that just seems its more trouble than it's worth.
Tip: do take a moment and rinse the stuff off your hands after or they'll look pickled later for a little while. I don't like this sensation so I always wash it off.
Best of healing to you!