I have been on sulfamerh/trimethoprim for 17 days. Have been off for 3 days now I have a wierd rash on my arms and legs can this be a penn. Reaction?

Maybe Med Reaction. Trimethorprim/ sulfamethoxazole is a sulfa based antiobiitic. Not a penicillin derivative. That said it is still a common source of allergy. Talk to your doc. It may very well be the drug. If your having any breathing difficulty go directly to your nearest er.