It sounds like it's breaking down and you're smelling the sulfur in it. I've tried the DMSO from CEM and it didn't have the notorious sulfur smell but it did burn if applied to the skin. I believe that the DMSO from lemelange is also USP grade but since it's repackaged it can no longer be claimed USP grade. From what I've read USP grade does not contain malodorous by products that give DMSO it bad smell. The USP grade DMSO gave me bad breath still so I'm assuming that's due to the sulfur breakdown in the system. Since yours didn't smell initially I'm assuming the same has happened. What kind of conditions was it stored in, hot or humid closet?