Head Lice

Overview

Head lice are tiny, wingless insects that live on the human scalp and feed on small amounts of blood. They are very common, especially among school-age children, and spread mainly through direct head-to-head contact. An infestation with head lice is called pediculosis capitis.

Adult lice are about the size of a sesame seed and can be hard to see. They lay eggs, called nits, which attach firmly to hair shafts close to the scalp. Head lice are a nuisance and can cause itching, but they are not dangerous and do not spread disease. Having head lice is not a sign of poor hygiene; anyone can get them. With proper treatment, head lice can be cleared effectively.

Symptoms

Some people with head lice have no symptoms at first. When symptoms occur, they include:

• Itching of the scalp, neck, and behind the ears, which is the body's reaction to louse bites
• A tickling feeling of something moving in the hair
• Visible lice on the scalp or hair (small, tan to grayish insects)
• Nits (eggs) firmly attached to hair shafts near the scalp, often mistaken for dandruff but not easily brushed off
• Small red bumps or irritation on the scalp, neck, or shoulders
• Difficulty sleeping, as lice are more active in the dark

Scratching can sometimes lead to sores and, occasionally, a secondary skin infection if the skin breaks.

Causes

Head lice are caused by infestation with the human head louse. They spread through:

• Direct head-to-head contact, the most common route, such as during play, sports, or sleepovers
• Less commonly, sharing items that touch the head, such as combs, brushes, hats, hair accessories, headphones, or pillows

Head lice cannot fly or jump; they crawl from one head to another. They live only on the human scalp and do not come from or live on pets. Lice that fall off a person usually die within a couple of days because they need regular blood meals from a human host to survive.

Risk Factors

Factors that increase the risk of getting head lice include:

• Being a child aged roughly 3 to 11 years, who have frequent close head contact
• Being a household member or close contact of someone with head lice
• Attending school or daycare
• Sharing hats, brushes, or bedding

Head lice affect people of all backgrounds and are not related to cleanliness or the length or type of hair. Children and the adults who care for them are most commonly affected.

Diagnosis

Head lice are diagnosed by finding live lice or nits in the hair. Because lice move quickly and avoid light, examination is best done carefully:

• Inspecting the scalp and hair, particularly behind the ears and at the back of the neck
• Using a fine-toothed nit comb on wet, conditioned hair, which makes lice easier to catch and see
• Distinguishing nits, which are firmly glued to the hair shaft, from dandruff or debris, which slide off easily

Finding a live louse confirms an active infestation. Nits alone, especially more than a short distance from the scalp, may be old and not indicate active lice, so finding live lice is the most reliable sign.

Treatment

Head lice are treated with medicated products and thorough combing. Treatment usually includes:

• Over-the-counter or prescription treatments: Medicated shampoos, lotions, or rinses that kill lice, applied according to the package instructions, often with a repeat treatment after about a week to catch newly hatched lice.
• Wet combing: Regularly combing wet, conditioned hair with a fine-toothed nit comb to remove lice and eggs; this can be used alone or with medication.
• Following directions carefully: Using the correct amount, timing, and any repeat application, since incomplete treatment is a common reason lice persist.
• Checking and treating close contacts: Examining household members and treating those who are infested.

If treatment fails despite correct use, a healthcare provider can recommend alternative prescription options.

Prevention

To help prevent the spread of head lice:

• Avoid head-to-head contact during play, sports, and sleepovers
• Do not share combs, brushes, hats, scarves, hair accessories, or headphones
• Check children's heads regularly, especially if lice are circulating at school
• Wash recently used clothing, bedding, and towels in hot water and dry on high heat, or seal non-washable items in a bag for a couple of weeks
• Soak combs and brushes in hot water
• Notify the school and close contacts so they can check and treat as needed

Extensive cleaning of the home is generally not necessary, since lice do not survive long away from the scalp.

When to See a Doctor

You can usually treat head lice at home with over-the-counter products. See a healthcare provider if:

• Over-the-counter treatments do not work despite correct use
• You are unsure whether lice are present
• The scalp becomes very red, swollen, painful, or oozing, suggesting a secondary skin infection
• The affected person is very young, pregnant, or has another condition that affects treatment choices

A provider can confirm the diagnosis, prescribe stronger treatment if needed, and treat any skin infection from scratching.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC).
2. American Academy of Pediatrics.
3. MedlinePlus, U.S. National Library of Medicine.