Head lice epidemiology and demographics

Template:Head lice Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Epidemiology and Demographics

Having head lice is very common. However, there are no reliable data on how many people get head lice in the United States each year.

Occasionally, head lice may be acquired from contact with clothing (such as hats, scarves, coats) or other personal items (such as brushes or towels) that belong to an infested person. Preschool and elementary-age children, 3-11, and their families are infested most often. Girls get head lice more often than boys, women more than men. In the United States, African-Americans rarely get head lice. Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice.

In the United States, infestation with head lice (Pediculus humanus capitis) is most common among preschool- and elementary school-age children and their household members and caretakers. Head lice are not known to transmit disease; however, secondary bacterial infection of the skin resulting from scratching can occur with any lice infestation.

Getting head lice is not related to cleanliness of the person or his or her environment.

Head lice are mainly spread by direct contact with the hair of an infested person. The most common way to get head lice is by head-to-head contact with a person who already has head lice. Such contact can be common among children during play at:

• school,
• home, and
• elsewhere (e.g., sports activities, playgrounds, camp, and slumber parties).

Uncommonly, transmission may occur by:

• wearing clothing, such as hats, scarves, coats, sports uniforms, or hair ribbons worn by an infested person;
• using infested combs, brushes or towels; or
• lying on a bed, couch, pillow, carpet, or stuffed animal that has recently been in contact with an infested person.

Reliable data on how many people get head lice each year in the United States are not available; however, an estimated 6 million to 12 million infestations occur each year in the United States among children 3 to 11 years of age. Some studies suggest that girls get head lice more often than boys, probably due to more frequent head-to-head contact.

In the United States, infestation with head lice is much less common among African-Americans than among persons of other races. The head louse found most frequently in the United States may have claws that are better adapted for grasping the shape and width of some types of hair but not others.