If patient is allergic to sulfisoxazole can he take MSM?

There are some possiblities that would negate an allergic reaction from the msm. First off, a seizure is not an allergic reaction to a drug. I am assuming that in 1955 this person was a child, and he may have had a febrile seizure from the illness for which he was taking the gantrisin. The other thing is that in msm its sulfur is a natural component to our body, and may not trigger a response. Allergic reactions to medication all have the same sypmtoms, throat and mouth swelling, hives, itching, eyes swelling, but not seizure. Just a question born of my curiosity, can he take Erythrocin? The inactive ingredient is sulfisoxazole.