It is true that this is used as a medium to transfer other drugs and solvents through the skin easily. That is why is must be used in a clean environment as it helps bacteria get through as well. It is actually used to help some cancers but the studies about long term use have not been done.
As for what they are using it for in the show industry. Along with the above action it is an anti-inflammatory as well and can reduce swelling. It is not a pain reduced but that is where I have heard some cattle people adding the drug gel Surpass to the area for pain relief on still or sore joints. No flames please. I have not nor would I do this but this is what I have heard it is being used for.