On April 10th 2008 I got a personal e-mail from Jim Humble
Here is the part in regards for DMSO
" I've used DMSO for a long time at 99.9% and have gotten good results.The minute you add anything to it,or the minute it hits your stomach it is no longer highly pure.
It is mixed with stomach acid and other juices.I don't see where the extra purity can affect anything ..."
Note-So I guess if you put DMSO on your skin then the purity could matter..But then again it might be worth paying a few extra $$$ for a garanteed quality product..