Head lice are tiny insects that live in human hair. They're particularly common in children.Head lice are whitish to grey-brown in colour, and smaller than the size of a pinhead when first hatched. When fully grown they're about the size of a sesame seed. They can't fly, jump or swim and are spread by head-to-head contact, climbing from the hair of an infected person to the hair of someone else.A head lice infestation isn't the result of dirty hair or poor hygiene. All types of hair can be affected, regardless of its length and condition.Head lice can usually be effectively treated with lotions or sprays designed to kill head lice, or by wet combing, using a specially designed head lice comb.Wet combing can be used without lotions or sprays, but it needs to be done regularly and can take a long time to do thoroughly.