Can you take Bactrim if your allergic to Vantin?

Hello everyone, I am new here and looking for help with a couple of questions if possible. Have read many topics and responses. Love the ideas and help that everyone gives.

My son is 22 yrs old and allergic to Vantin, when he was 2 yrs old his Dr gave him Vantin when he had a double ear infection. He broke out in one huge rash covering his face, chest, tummy, and back. They kept telling me over the years that he should possibly grow out of it??

Over the last 20 yrs he hasn't had to take any antibiotics, that I recall. But now he has to have a tooth removed and the dentist gave him a prescription for Bactrim. I reminded him of his allergies from 20 yrs before, and the dentist said he would be fine, didn't sound to convincing to me or I just over assume things at times.

I'm looking to find out if you can take Bactrim if your a allergic to Vantin?

Vantin, now discontinued, was a cephalosporin. Bactrim is a combination of a sulfonamide and another antibiotic. They are not in the same class.

Check with your pharmacist.