The painful reaction started in the middle of the night. September Norman of Hendersonville, Tennessee, remembers waking up “itching like a fiend.”

“I thought something had bitten me and I tried drinking water to flush it out,” she says. A couple of hours later, her lips and tongue swelled up. Frightened, she woke her husband. “He took one look at me and said we have to go get help.” EMS workers later told Norman she might have died if she’d gone without treatment for another 20 minutes.