How long is chickenpox contagious?

The incubation period for varicella-zoster virus (VZV), which causes chickenpox, is usually 10-21 days. A person with chickenpox is contagious from 1-2 days before the rash appears until all the blisters have crusted over, usually 5-7 days after the rash appears. People with chickenpox are most contagious in the 2-4 days after the rash appears.