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Head lice

Quick facts

  • Head lice, Pediculus humanus capitis, are a common problem, especially on children.
  • They do not carry diseases but their biting can cause considerable itching.
  • People get head lice only from other infested people.
  • To help prevent the spread of head lice, do not share combs, brushes, scarves, clothing, hats, towels or similar items.
  • Physical removal can help control head lice.
  • You can buy special shampoos to treat head lice, either over-the-counter or by prescription from a doctor.

Why are head lice important?

Adult head louse.
Adult head louse

Who is at risk?

  • Head lice are most commonly a problem for children, but adults can get head lice.  
  • Head lice can spread quickly between children because they do things that help lice spread—such as sharing hats or combs.
  • Lice only infect humans, so pets are not at risk of catching head lice.
  • Head lice only infest the head area, other types of lice are associated with other locations on the human body.

What do head lice do?

  • Head lice spend their whole lives on our head where the adults and nymphs feed on blood. 
  • The bites are painless and cannot be felt at all, but our bodies can react to the saliva injected when they bite. For most people this causes intense itching, like the itch of mosquito bites.   
  • Head lice feed multiple times a day so there are many bites that itch.
  • Head lice do not carry any diseases and are not known to spread any diseases between humans.
  • Having head lice can be a source of embarrassment and it takes time to get rid of them. 
  • Children with head lice may have to miss school depending on the school district's policy about lice.

How to identify head lice

Correct identification of head lice is very important as other insects or even debris, like bits of skin or scabs, may be confused for head lice.

Louse egg (nit) on a strand of hair.
Nit on a strand of hair

Adult head lice

  • Small, about 1/8-inch-long (about the size of a sesame seed).
  • Grayish, flattened bodies; wingless.
  • They have claw-like legs to more easily hold onto hair.

Immature head lice (nymphs)

  • Look the same as adults but are smaller.

Nits (lice eggs)

  • Whitish, oval and the size of a pinhead (1/30 inch long).
  • They are firmly attached to the hair shaft near the scalp.
  • Nits do not move, but as hair grows they move out from the scalp.
    • Nits found further than 1/2 inch from the scalp nearly always have hatched or died.
  • Nits are the easiest life-stage to search for in order to confirm head lice infestation.
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How to tell if you have head lice

The most common symptom is itching. It typically starts about 4 to 6 weeks after the first bite. However, not everyone is allergic to bites and infestations can go unnoticed for a while.

Itching can alert you that head lice may be a problem. To verify a head lice infestation, it is necessary to find live lice on the hair or scalp of a person.

The presence of nits also confirms a head lice problem. Look especially at the nape of the neck and behind the ears. If the nits are more than 1/4 inch from the scalp, they likely have either hatched or are dead.

Don’t confuse head lice or nits with dandruff, scabs or other debris. Be sure head lice are confirmed before treating a person.

How to control head lice

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Jeff Hahn, Extension entomologist, and Laura Iles, Iowa State University

Reviewed in 2020

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