Head lice (Pediculus humanus capitis) are tiny wingless parasitic insects that infest humans. They typically live in the hair and feed on blood from the scalp.

The most common sign of an active infestation is the appearance of lice eggs in the hair, which can resemble dandruff. The eggs are glued to the shaft of the hair follicle in casings called nits, found particularly on the hair behind the ears and back of the scalp.

Infestation is most common in school-aged children with girls being more commonly affected than boys. African-American children are less often affected; this variation is thought to be the result of differences in the hair shaft structure, which may be oval shaped and thus more difficult for a louse to grasp.

Lice are spread through close physical contact, but can also be spread through shared personal items as well. Although lice are generally not dangerous and don’t carry any infectious diseases, they can be extremely irritating and itchy.

Common symptoms of head lice include:

Inflammation and itching: During feeding, lice will puncture the skin and inject their saliva. For many, this causes an allergic reaction resulting in small red inflamed bumps and low-grade itching.

Adult Lice and Nits: During an infestation, adult lice and nits are visible in the hair. The adult lice are usually found in areas around the back of the neck and around the ears. Nits can be found close to the scalp, attached to the hair follicles, and can resemble dandruff.

Infestations of head lice are typically caused by direct head-to-head contact. They may also be transferred by sharing bedding or personal items such as hats, scarves, combs, brushes and headphones. It is not related to the lack of hygiene. Louse transfer has been found to be optimal when hairs are relatively stationary and parallel, suggesting that louse transmission is more likely to occur while children are at rest, than during periods of vigorous play.

Good hair care is essential in treating head lice. Make sure to thoroughly wash and rinse your hair. Use a shampoo specially designed for the treatment of lice. After bathing, use a fine-toothed comb to brush out lice and nits from wet hair. The nits are difficult to remove, so it’s important to carefully and diligently comb through all areas of the hair.

Getting children to avoid close contact with one another in a school setting is an unrealistic expectation. However, you can encourage them not to share personal items such as combs, hats, scarves and hair decorations, which can transfer lice and nits.

Over-the-counter shampoos containing pyrethrin (Rid) or permethrin (Nix) are usually effective for treating lice. Some products work by dissolving the outer layer of wax in the outside walls of the nits. Non chemical therapies have also been developed that dissolve the wax making the up the body of the louse.

For more severe or persistent cases of head lice, a doctor may prescribe a topical medicated lotion containing Malathion and Lindane. Oral drugs such as Ivermectin and TMP/SMX have also shown to be effective in treating lice.