So Sunday I got a uti. Have had several of them in the past so I went to the doctor and knew I was gonna get cipro or Bactrim which is fine... I always take those. Was on bactrim in october of 2017 and it cleared my infection. So yesterday I got a prescription of generic bactrim like normal. Took the first one and was fine. This morning when I took it I noticed an itchy feeling in my lips and I looked in the mirror to see slight swelling. I feel fine other wise but what could be going on... is it possible to randomly become allergic to a medicine even after taking it for years??