Head lice are parasites and need human blood in order to survive. They live in a host's hair for about 30 days and during that time a female Louse can lay up to 100 eggs. A Louse cannot survive more than 24 hours when off of a host. Lice cannot hop, jump or fly. They are spread by crawling from person to person. Head lice cause itching on the head and/or neck and can sometimes cause a rash. A person with Head lice can be infected for awhile without itching and some people may not itch at all. Head lice rarely spread disease or illness.