Used it on a lump on my horses back under the vets advice, did reduce swelling but didn't get rid of it completely. Time was the true healer but think the DMSO did help especially with the initial swelling.
DMSO is also a carrying agent. If you use it with something else it 'carrys' it through the skin etc. Thats why if you don't use gloves you can often get a funny taste in your mouth!
I seem to think we used it on a tendon injury - rubbed into the skin. Was only about 13 at time so details hazy. I know the pony started licking at it and the legs ended up blistered and raw.