Head lice are tiny insects that live on the scalp where they lay their eggs. They have three stages: the egg (nit), the nymph and the adult. Head lice do not spread diseases and cannot be spread between animals or pets and humans, only through direct contact between people.
Head lice spread easily, especially where people are in close contact. They are very common among school-aged children or children attending child care, where they spread through direct hair-to-hair contact or directly by sharing things like hats, combs, hairbrushes or headphones.