Lice

Lice are small, wingless parasitic insects that live on the bodies of humans and other mammals, feeding on blood. There are three species commonly affecting humans: head lice (Pediculus humanus capitis), body lice (Pediculus humanus corporis), and pubic lice (Pthirus pubis). Head lice attach to scalp hair, body lice inhabit clothing and migrate to the body to feed, and pubic lice reside in coarse body hair.

The life cycle begins when a female louse lays eggs, or nits, cemented to hair shafts near the skin. Nits hatch after about 7 to 10 days, producing nymphs that molt three times before becoming adults. Adults live for roughly 30 days and die when separated from a host. Lice spend their entire life cycle on the host and do not fly or jump.

Transmission occurs mainly through direct contact with an infested person. Head lice spread most often among children through close contact. Body lice are associated with crowded or unsanitary conditions and spread via contaminated clothing or bedding. Pubic lice are usually transmitted through sexual contact or shared infested belongings. Symptoms typically include intense itching; visible lice or nits on hair, especially near the scalp (head) or body hair (body), and scratching that can lead to skin irritation or secondary infection.

Diagnosis is usually made by examining the hair and scalp for lice and nits, sometimes aided by wet combing. Treatment uses topical pediculicides, such as products containing pyrethrins or permethrin, with alternative medications available in parts of the world. After treatment, removing nits with a fine comb and laundering clothing, bedding, and upholstered items at high temperatures helps prevent reinfestation. Regular screening and avoiding the sharing of personal items reduce spread.