How long after you've had a cold are you still contagious?

Unclear. Many different viruses can cause an upper respiratory infection (cold), each with a differing course. The time of highest viral shedding and contagiousness is usually days 2-4 of the infection, and shedding usually continues to decrease after that, but does still occur until symptoms resolve. Interestingly, using Aspirin can actually increase your viral shedding and increase the chance of spread.