How long does it take before THC enters your hair after smoking one time?

i don't know the "scientific answer" to this question, but i know from experience that if you wash your hair a lot then the weed wont be in your hair and it doesn't smell like it at all if you don't smoke weed that day. you really don't have anything to worry about with that, but i'd worry about the yellow fingers and teeth, that's a nasty one.