Head lice affect all socioeconomic classes and diverse groups of people worldwide. According to the Centers for Disease Control (CDC), personal and environmental hygiene are not risk factors for head lice infestation. In fact, the greatest risk factor for contracting head lice is head-to-head contact.  For that reason, children are the most at risk. The CDC estimates that approximately 6-12 million cases of head lice occur in the United States yearly, mainly in children ages 3-11 years old. Importantly, head lice do not spread other disease.

Anyone can get head lice, even celebrities. Even major celebrities have shared their personal family experiences with head lice infestation.

What are head lice?

A singe louse

The adult head louse is approximately the size of a sesame seed, 2 mm in length. Adult lice are grey/tan in color. Lice move by crawling. Contrary to popular belief, lice do not hop or fly.

Lice have a life cycle. An adult louse can lay 50-100 eggs. The eggs mature over the course of 7-10 days to become a nymph, or intermediate form. Over approximately 10 days, the nymphs mature to be adult lice and then the cycle starts all over again.

Lice feed on blood from the scalp. While the louse is feeding, its saliva gets mixed into the host’s blood and can cause a localized reaction causing an itchy rash. The itch reaction may be delayed 4-6 weeks from initial infestation. See areas of irritation on the scalp below.

What are symptoms of head lice in a child?

  • Itchy head
  • Tickling feeling or a sensation of something moving in the hair
  • Irritability and sleeplessness
  • Sores on the head caused by scratching
  • Some infestations have no symptoms

How do you detect head lice?

Adult lice move quickly and often are hard to see. When screening for lice, comb through the hair to look for lice. You are more likely to see the white lice eggs in the hair. Lice tend to lay their eggs behind the ears and around the base of the head. They appear as white specks attached to the base of the hair shaft. Unlike dandruff, sand, or hairspray particles, the eggs cannot be shaken off from the hair shafts.

How do you get rid of lice?

The Centers for Disease Control recommends treating all individuals with active lice infection. Over-the-counter (OTC) medications such as Nix® or Rid® are the first line treatment for head lice. You only need to use one of them.  It is important to note that these medications only kill the nymph and adult states; therefore, a second treatment is needed approximately 7-9 days later to kill the developing eggs.

Rid®, otherwise known as pyrethrins combined with piperonyl butoxide, is approved for use in children 2 years and older. It should not be used by persons who are allergic to chrysanthemums or ragweed. A second application of the medication should be done approximately 9 days later.

Nix®, otherwise known as permethrin 1%, is approved for use in children 2 months and older. Just like Rid, a second application should be done approximately 9 days later.

There are prescription medications available as well, but it is recommended to first try using an over-the-counter product.

It is also important to check all household members or close contacts for head lice as well.

How do you apply the OTC lice medications?

OTC medications are the consistency of a cream rinse. It is important to not use a combination shampoo or conditioner before using lice medicine. Make sure you follow instructions closely. When rinsing off the medication, do so over a sink rather than in the shower to avoid getting the medication all over your child’s body. It is also very important to protect their eyes when rinsing off. You will want to comb dead and any remaining live lice out of the hair using a fine–toothed nit comb that often comes with the lice medication. Make sure the treated person puts on clean clothing after treatment. Do not re–wash the hair for 1–2 days after the lice medicine is removed.

How do you prevent further spread of head lice?

The key to preventing the spread of head lice is avoiding head-to-head contact with an infected person.

It is also important to launder items worn or used by person two days prior to treatment, such as hats, scarves, pillow cases, bedding, clothing, and towels. Machine wash items using hot water (130˚ F) and use the high heat setting for drying.

If items cannot be laundered, send them to the dry cleaner or seal them in a plastic bag for 2 weeks.

Avoid sharing hats, brushes, combs, or towels of affected person.

Vacuuming the floor and furniture where the infested person sat or lay is helpful. Please do not use fumigation sprays or fogs.  They are not necessary to control head lice and can be dangerous if inhaled or absorbed through the skin.

How long can lice survive without a host?

Head lice survive less than 1–2 days if they fall off a person and cannot feed. The lice eggs cannot hatch and usually die within a week if they are not kept at the same temperature as that found close to the scalp.


Written by Ashley DeHudy, MD

Updated March 2017