Can bactrim (sulfamethoxazole and trimethoprim) cause a rash after using it for 10 days?

Likely during use.: A person can have a rash from Bactrim (sulfamethoxazole and trimethoprim) or any other drug, but it likely developed during the course of the drug, not after. It may have been too subtle at first, and could have been attributed to other things, like food allergy or contact allergy from clothes washed with a detergents that can cause a rash in those who are susceptable.

Yes, if first time.: Drug rashes usually develop within two weeks of initial exposure to a new medication, but they may sometimes be delayed by a week. Re-challenge with the same medication may produce a rash that shows up immediately after ingestion.