Head lice

Head lice are tiny insects that feed on blood from the human scalp. Head lice most often affect children. The insects usually spread through direct transfer from the hair of one person to the hair of another.

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

Nonprescription and prescription medications can help treat head lice. Follow treatment instructions carefully to rid the scalp and hair of lice and their eggs.

People also use a number of home or natural remedies to get rid of head lice. But there is little to no clinical evidence that they're effective.

Common signs and symptoms of head lice may include:

• Itching. The most common symptom of head lice is itching on the scalp, neck and ears. This is an allergic reaction to louse bites. When a person has head lice for the first time, itching may not occur for 4 to 6 weeks.
• Lice on scalp. You may be able to see the lice, but they're often hard to spot because they're small, avoid light and move quickly.
• Lice eggs (nits) on hair shafts. Nits stick to hair shafts and may be hard 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 mean there are live lice.
• Sores on the scalp, neck and shoulders. Scratching can lead to small, red bumps that may sometimes get infected with bacteria.

See a health care provider before you begin treatment if you suspect that you or your child has head lice. Your or your child's health care provider can confirm that head lice are present. Studies show that many children have been treated for head lice with nonprescription medications or home remedies when they didn't have lice.

Things often mistaken for nits include:

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

A head louse is a tan or grayish insect about the size of a strawberry seed. It feeds on human blood from the scalp. The female louse produces a sticky substance that firmly attaches each egg to the base of a hair shaft less than 1/4 inch (5 millimeters) from the scalp.

The louse life cycle

A louse goes through three stages:

• Eggs that hatch after 6 to 9 days.
• Nymphs, immature forms of the louse that become mature adults after 9 to 12 days.
• Adult lice, which can live for 3 to 4 weeks. The female louse lays 6 to 10 eggs a day.

Transmission

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

It's less common for head lice to spread without direct contact. But the insects may spread from one person to another through personal items, such as:

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

Head lice may also spread when items of clothing are stored together. For example, hats or scarves hung on the same hook or stored in the same school locker could serve as vehicles for spreading lice.

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

Head lice are spread primarily by direct head-to-head contact. So the risk of spreading head lice is greatest among children 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.

If your child scratches an itchy scalp due to head lice, it's possible for the skin to break and develop an infection.

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 spread from personal items is slight. However, to help prevent head lice from spreading, you may tell your child to:

• Hang clothes on a separate hook from other children's clothes
• Avoid sharing combs, brushes, hats and scarves
• Avoid lying on beds, couches or pillows that have been in contact with a person who has head lice

It's not necessary to avoid sharing protective headgear for sports and bicycling when sharing is required.