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Head lice

Head lice are tiny insects that live on the scalp, where they lay their eggs. Head lice do not spread disease. Having head lice does not mean you are not clean.

What do head lice look like?

Lice have 3 stages – the egg (nit), the nymph and the adult.

  • Nits are whitish-grey, tan or yellow ovals, approximately the size of a grain of sand. They stick to the hair close to the scalp and can look like dandruff. Nits hatch in 9 to 10 days.
  • Nymphs are baby lice. They look like adult lice but are smaller.
  • Adult lice are approximately the size of a sesame seed and are hard to see. Adult lice can live for up to 30 days on a person’s head, but they die within 3 days away from the scalp. 

How do they spread?

Head lice spread easily, especially where people are in close contact. They are very common among school-aged children or children attending child care.

  • Head lice spread through direct hair-to-hair contact or indirectly by sharing things like hats, combs, hairbrushes and headphones.
  • Head lice don’t fly or hop, but do crawl very quickly.
  • Head lice that live on people can’t live on pets, such as cats or dogs.

How do you know you have head lice?

One of the first signs of head lice is an itchy scalp. But it is possible to have head lice without any symptoms.

If you think your child has head lice, check his hair for nits right away, then again after 1 week and after 2 weeks.

How do I check for head lice?

To confirm a case of head lice, you need to find live lice. Children can have a few nits without actually having a case of head lice. Usually children have no more than 10 to 20 live lice.

  • Good lighting is important when you are checking.
  • Head lice move fast and are hard to see. They are usually found very close to the scalp, at the bottom of the neck and behind the ears.
  • To look for nits, part hair in small sections, moving from one side of the head to the other. Check carefully, looking close to the scalp.   

How can head lice be treated?

Insecticides are chemicals that kill insects (bugs). In Canada, 3 insecticides are approved to treat head lice:

  • pyrethrin (found in R&C Shampoo + Conditioner)
  • permethrin (Nix Creme Rinse or Kwellada-P Creme Rinse)
  • lindane (Hexit Shampoo or PMS-Lindane Shampoo).

Pyrethrin and permethrin are safe when used on humans. However, lindane can be toxic (poisonous). Products with lindane should not be used on infants or young children younger than 2 years of age. You don’t need a prescription for these products.

  • Follow package directions carefully.
  • Don’t leave the shampoo or rinse in the hair longer than directed.
  • Rinse hair well with cool water after the treatment. It’s best to rinse over a sink, not in the bath or shower, so that other parts of the body don’t come in contact with the product.
  • Repeat the treatment after 7 to 10 days.

Sometimes, these treatments can make the scalp itchy or can leave a mild burning feeling. If your child is scratching after treatment, it does not necessarily mean the lice are back.

A noninsecticidal product called isopropyl myristate/cyclomethicone (Resultz) has also been approved for use in Canada, but it should only be used in children 4 years of age and older:

It works by breaking down the waxy exoskeleton (‘skin’) of lice. The lice get dehydrated and die.

  • Apply to a dry scalp and rinse after 10 min.
  • Repeat after 1 week.

Do not treat anyone with a head lice product unless you find lice in their hair. Check all family members if someone in the house has head lice.

What about other treatments?

  • Some people use home remedies such as mayonnaise, petroleum jelly, olive oil, vinegar or margarine. Although these products may make it hard for lice to breathe, they probably won’t kill them.
  • There is very little evidence that wet combing works (removing lice by combing wet hair with a fine-tooth comb).
  • There is no evidence that products such as tea tree oil or aromatherapy work to treat head lice.
  • Never use gasoline or kerosene. These products can be extremely dangerous.

Should the house be disinfected if someone has head lice?

Because head lice don’t live long off the scalp, there is no need for extra cleaning.

To get rid of lice or nits from items like hats or pillowcases:

  • Wash the items in hot water and dry in a hot dryer for 15 min; or
  • Store the items in an airtight plastic bag for 2 weeks.

Should children with head lice stay home from school?

Children with head lice should be treated and can attend school or child care as usual.

‘No-nit’ policies that keep children with head lice away from school are not necessary because:

  • Head lice are common among young children.
  • Head lice don’t spread disease.
  • Cases of head lice are often misdiagnosed.
  • Children can have head lice for several weeks with no symptoms.

If your child has head lice, treat it. Teach your child to avoid head-to-head contact with other children until the lice are gone. Children should not share combs, hairbrushes, caps, hats or hair ornaments.



Reviewed by the following CPS committees:
Infectious Diseases and Immunization Committee

Last Updated: October 2008