My personal opinion of DMSO is that it should only be used under a vet's direction and/or by horse folks that are very experienced in dealing with serious injuries and have a clear understanding of what DMSO is.
DMSO carries "things" into the blood stream, so use of it has to be done in as sterile conditions as possible. It is not meant for long-term use.
I have only used it once in my entire life of owning horses. It was for a very severe hoof/pastern injury and with the strictest of instructions from my vet. That was three years ago and I still have nearly 3/4 of an 8 ounce bottle left in the cupboard.
That all being said, I also have a jar of people DMSO at the house. I buy it at the old folks health food store and it is in gel form.
I only use it in the winter when it's cold and my old joints start locking up. And then only after a bath and my skin is clean.
The other DMSO option also came from a vet:
In a 32 ounce bottle of Absorbine, add a teaspoon of DMSO and several drops of wintergreen. Shake well before using and apply sparingly NOT liberally :)
That is just my opinion. I have spent the bulk of my life wearing a "No Fear" t-shirt, but there are some things I approach with caution --- DMSO is one of them