Chlorhexidine
"As part of my pre-op, I was instructed to use from neck to toes, avoiding mucous membranes & genital area.  Three hours later my nose began to really itch.  Have seasonal allergies so didn't think too much about it. Through pre- op the itching got worse.  When I came out of surgery itching was much worse & upper lip swollen. By the time I got home, itching, swelling worse and everywhere I had used the chlorhexidine wash was red and felt like I had a bad sunburn.  Took Benadryl which reduced symptoms. Had to take it for 3 days to stop symptoms from coming back. "