what causes lice
The cause of lice (known medically as pediculosis) is an infestation with one of three types of a parasitic insect. The three kinds of lice that affect humans include: 1  Pediculus humanus capitis (head lice). 2  Pediculus humanus corporis (body lice). 3  Phthirus pubis (pubic lice or crab lice; also called crabs).he three kinds of lice that affect humans include: 1  Pediculus humanus capitis (head lice). 2  Pediculus humanus corporis (body lice). 3  Phthirus pubis (pubic lice or crab lice; also called crabs).