Head lice are tiny parasitic insects that can lodge in various parts of the human body and lay eggs. Pediculosis is the name given to the contagious parasitic infestation of the skin caused by lice. Lice attack by biting the skin what usually causes itching. One of the favorite places of head lice is the scalp. Pediculosis is common but remains minor while being very uncomfortable, especially because of its degree of contagion. In 40% to 50% of cases of lice on the scalp, there is no itching. Young children are most likely to be infected with lice.