Overview

Head lice are tiny insects that feed on blood from the human scalp. An infestation of head lice most often affects children and usually results from the direct transfer of lice from the hair of one person to the hair of another.

A head-lice infestation isn't a sign of poor personal hygiene or an unclean living environment. Head lice don't carry bacterial or viral infectious diseases.

Over-the-counter and prescription medications are available to treat head lice. Follow treatment instructions carefully to rid your scalp and hair of lice and their eggs.

A number of home or natural remedies are also used to treat head-lice infestations, but there is little to no clinical evidence of their effectiveness.

Symptoms

Common signs and symptoms of a lice infestation can include:

  • Itching. The most common symptom of a lice infestation is itching on the scalp, neck and ears. This is an allergic reaction to louse bites. When a person has a lice infestation for the first time, itching may not occur for four to six weeks after infestation.
  • Lice on scalp. Lice may be visible but are difficult to spot because they're small, avoid light and move quickly.
  • Lice eggs (nits) on hair shafts. Nits stick to hair shafts. Incubating nits may be difficult to see because they're very tiny. They're easiest to spot around the ears and the hairline of the neck. Empty nits may be easier to spot because they're lighter in color and further from the scalp. However, the presence of nits doesn't necessarily indicate an active infestation.
  • Sores on the scalp, neck and shoulders. Scratching can lead to small, red bumps that may sometimes get infected with bacteria.

When to see a doctor

See your doctor before you begin treatment if you suspect that you or your child has a head-lice infestation. Studies show that many children have been treated for head lice with over-the-counter medications or home remedies when they don't have an active head-lice infestation.

Things often mistaken for nits include:

  • Dandruff
  • Residue from hair products
  • Bead of dead hair tissue on a hair shaft (hair cast)
  • Scabs, dirt or other debris
  • Other small insects found in the hair

Causes

A head louse is a tan or grayish insect about the size of a strawberry seed. It feeds on human blood from a person's scalp. The female louse produces a sticky substance that firmly attaches each egg to the base of a hair shaft no more than 3/16 inch (5 millimeters) from the scalp.

The louse life cycle

A louse goes through three stages:

  • Eggs that hatch after six to nine days.
  • Nymphs, immature forms of the louse that become mature adults after nine to 12 days.
  • Adult lice, which can live for three to four weeks. The female louse lays six to 10 eggs a day.

Transmission

Head lice crawl, but they can't jump or fly. Transmission of a head louse from one person to another is often by direct head-to-head contact, often within a family or among children who have close contact at school or play.

Indirect transmission is uncommon, but lice may spread from one person to another by items such as:

  • Hats and scarves
  • Brushes and combs
  • Hair accessories
  • Headphones
  • Pillows, towels and upholstery

Indirect transfer could also occur among items of clothing stored together. For example, hats or scarves hung on the same hook or stored in the same school locker could serve as vehicles for transmitting lice.

Household pets, such as dogs and cats, don't play a role in spreading head lice.

Risk factors

Because head lice are spread primarily by direct head-to-head contact, the risk of transmission is greatest among younger people who play or go to school together. In the United States, cases of head lice most often occur in children in preschool through elementary school.

Complications

If your child scratches an itchy scalp from a head-lice infestation, it is possible for the skin to break and develop an infection.

Prevention

It's difficult to prevent the spread of head lice among children in child care facilities and schools because there is so much close contact.

The chance of indirect transmission from personal items is slight. However, to help prevent a head-lice infestation, you may instruct your child to:

  • Hang garments on a separate hook from other children's garments
  • Avoid sharing combs, brushes, hats and scarves
  • Not lie on beds, couches or pillows that have been in contact with a person infested by head lice

A worry about head-lice transmission is not considered a good reason to avoid sharing protective headgear for sports and bicycling when sharing is necessary.

More Information

April 16, 2020
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