Head Louse

Exclusively on the human scalp and hair.

Human blood

Head lice spend their entire life cycle on the human scalp, feeding on blood multiple times a day. They cannot jump or fly, but crawl from head to head, typically through direct head-to-head contact. Nits (eggs) are laid and cemented to hair shafts close to the scalp. After hatching, nymphs mature into adults in about a week. Adults live for about 30 days and continually lay eggs. Infestations lead to itching, which is the body's allergic reaction to the louse saliva.

Potential risks include intense itching, discomfort, and secondary bacterial infections due to scratching. Head lice do not transmit diseases to humans. There are no known benefits.