What are the side effects from taking bactrim (sulfamethoxazole and trimethoprim)? i am noticing small red bumps (that itch) on my arms and legs, diarrhea, headaches, and pains.

Bactrim (sulfamethoxazole and trimethoprim) side effects: It may be an allergic reaction to bactrim, (sulfamethoxazole and trimethoprim) and you should stop it immediately and call your doctor.

Sulfa rash: You are describing a possible sulfa drug reaction with the bumps on the arms and legs contact your prescribing physician to get an alternative antibiotic.