Pediculus humanus

Overview

A male human head louse

The human head louse (Pediculus humanus capitis) is a parasitic insect that can be found on the head, eyebrows, and eyelashes of people. Head lice feed on human blood several times a day and live close to the human scalp. They are a common problem, especially among children, and are spread mainly through direct head-to-head contact.

Biology

The head louse is a wingless insect that belongs to the order Phthiraptera. It has six legs adapted for clinging to hair. The adult louse is about 2–3 mm long, with a tan to grayish-white color. Female lice are usually larger than males and can lay up to 10 eggs per day.

Life Cycle

The life cycle of the head louse consists of three stages: egg (also known as a nit), nymph, and adult. Nits are lice eggs that are laid by the adult female at the base of the hair shaft. They are firmly attached to the hair and are oval and usually yellow to white. Nymphs are immature lice that hatch from the nits. They look like adult lice but are smaller. Nymphs mature into adults about 9-12 days after hatching.

Transmission

Head lice are spread primarily through direct head-to-head contact. They cannot jump or fly, but they can crawl. Sharing personal items such as hats, combs, or hair accessories can also facilitate the spread of lice, although this is less common.

Symptoms

The most common symptom of head lice infestation is itching, which is caused by an allergic reaction to the bites. Other symptoms may include a tickling feeling of something moving in the hair, irritability, and difficulty sleeping (lice are more active in the dark).

Diagnosis

Diagnosis of head lice infestation is made by finding a live nymph or adult louse on the scalp or hair. Nits alone are not sufficient for diagnosis, as they may be empty or dead.

Treatment

Treatment for head lice typically involves the use of over-the-counter or prescription medications that kill lice. These treatments may be in the form of shampoos, lotions, or creams. It is important to follow the instructions carefully and to repeat the treatment as recommended to ensure all lice and nits are eliminated.

Prevention

Preventing head lice involves avoiding head-to-head contact during play and other activities. Regular checking of children's hair for lice and nits can help catch infestations early. Educating children about not sharing personal items that touch the head can also help reduce the spread of lice.

Related pages

• Pediculosis
• Phthiraptera
• Parasite