Depending on the degree of severity of your allergy, I don't think you should 'experiment' with it.
Even without the DMSO, the gel works just as good as Avantlab's. So it is not like you won't benefit w/o the DMSO.
This one of the few intelligent questions I have heard asked here in quite some time. Man good for you for looking for an answer. I know we have moved a lot away from Sulfa but to be on the safe side stay away until you are sure. Sorry bro don't know the answer straight off the top of my head on this one.
Don't use it if you're allergic to sulfa, you should also stay away from MSM.