Contagiousness

Chickenpox is contagious from about 2 days before the rash appears and lasts until all the blisters are crusted over. A child with chickenpox should be kept out of school until all blisters have dried, usually about 1 week. If you're unsure about whether your child is ready to return to school, ask your doctor.

Chickenpox is very contagious — most kids with a sibling who's been infected will get it as well, showing symptoms about 2 weeks after the first child does. To help keep the virus from spreading, make sure your kids wash their hands frequently, particularly before eating and after using the bathroom. And keep a child with chickenpox away from unvaccinated siblings as much as possible.

People who haven't had chickenpox also can catch it from someone with shingles, but they cannot catch shingles itself. That's because shingles can only develop from a reactivation of VZV in someone who has previously had chickenpox.