Child with glasses scratching head against a gray background

What Are Lice?

Lice are a common family issue. These tiny insects live on the scalp (and sometimes eyebrows or lashes), feeding on blood. Their bites don’t hurt but can cause intense itching and allergic reactions.

Life Stages of Lice

Illustration of a lice nit.

Nits

Eggs, called nits, are tiny and attach to hair near the scalp.

Illustration of a lice nymph.

Nymphs

Nits hatch in about 7–10 days into young lice called nymphs.

Illustration of an adult louse.

Adult Lice

Nymphs grow into adult lice within about a week, and adult lice can live up to 30 days on the scalp and lay new eggs, continuing the cycle.

A woman checking her daughter's hair for lice.

How Common are Lice?

The Centers for Disease Control and Prevention (CDC) estimate that up to twelve million children aged 3 to 11 contract lice in the United States each year. However, anyone can get head lice and they are found worldwide.

Learn About Effective Treatments

What are the symptoms of Lice?

Itching on the areas where head lice are present is the most common symptom. It may take up to 4-6 weeks after lice get on the scalp before the scalp becomes sensitive to the lice saliva causing the itching. Itching caused by head lice can last for weeks, even after the lice are gone. Symptoms may include:

Itching
boy itching his head

Itching

Lice symptoms may include persistent itching or a tickling sensation in the hair, often caused by the movement of lice on the scalp.

Trouble Sleeping
Child lying on a bed with hands covering eyes

Trouble Sleeping

They can also lead to irritability or difficulty sleeping, especially as the itching worsens at night.

Irritation
A young girl holding her head in her hands.

Irritation

Excessive scratching of the scalp may result in sores or skin irritation, which can sometimes become infected if not treated properly.
Children with backpacks in front of a yellow school bus

How do Lice Spread?

The most common way to get head lice is by head-to-head contact with a person who already has head lice. This contact can be common among children playing at places like school, camp, or in the home. Lice move by crawling; they cannot hop or fly. Although not as common, lice may spread by wearing clothing or hats, sharing combs, or using linens recently used by an infested person.