7 Things You Don't Know About Colds

With colds, you're most likely to infect other people two to four days after you first feel symptoms, Collins says. So the violent sneezing, coughing, honking into tissues—they're your body's way of announcing to healthy folk that you're contagious and they'd be wise to keep their distance. (The flu, on the other hand, can be passed along one day before any symptoms appear, as well as up to five to seven days after a person feels sick, so you could be contagious and not know it.) When someone shoots you a dirty look for coughing too loudly, remind yourself that you're doing them a favor.