Head lice are tiny insects that live on the scalp, where they lay eggs. Head lice do not spread disease. It's not your fault if you or your child has head lice.
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, about the size of a grain of sand. They stick to the hair close to the scalp and can look like dandruff. Nits hatch into nymphs in 9 to 10 days.
- Nymphs are baby lice. They look like adult lice but smaller.
- Adult lice are hard to see since they are about the size of a sesame seed. Adult lice can live for up to 30 days on a person’s head, but they die within 2 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 in child care.
- Head lice spread through direct hair-to-hair contact or indirectly by sharing hats, combs, hairbrushes and headphones.
- Head lice don’t fly or hop, but crawl very quickly.
- The head lice that live on people are different from the kind that live on cats or dogs. People cannot get head lice from animals.
How do you know you have head lice?
One of the first signs of head lice is an itchy scalp, but it’s possible to have head lice without any symptoms. Most itchy scalps are not from head lice. If your child has an itchy scalp or was exposed to head lice, check his hair right away. Check again once a week for 2 weeks in case you missed them.
How do I check for head lice?
Look carefully through the hair for live lice and nits. If you only find nits, your child may not have head lice. Usually children have no more than 10 to 20 live lice.
- Because lice are so small, good lighting is important. A magnifying glass may help.
- Head lice move fast and are hard to see. You may just see movement rather than the actual lice. Lice 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. Look close to the scalp. If you only find nits and no lice, check again every day for 1 week to make sure that you did not miss any live lice.
How can I treat head lice?
Do not treat anyone with a head lice product unless you find live lice in their hair. If someone in the house has lice, check all family members.
Head lice can be treated in a variety of ways:
Insecticides are chemicals that kill insects. In Canada, 2 insecticides are approved to treat head lice:
- pyrethrin (found in R&C shampoo + conditioner)
- permethrin (Nix creme rinse or Kwellada-P creme rinse)
Pyrethrin and permethrin are safe when used on humans over two months old. You do not need a prescription. Over time, head lice have become resistant to some of the chemicals used to kill them. So some products may be less effective than they used to be. But they are still worth trying.
How to apply insecticides:
- Follow package directions carefully.
- Don’t leave the shampoo or rinse in the hair longer than directed.
- Rinse hair with cool water after the treatment. It’s best to rinse over a sink, not in the bath or shower, so that other body parts don’t come in contact with the product.
- Repeat the treatment after 7 to 10 days, in case new lice hatched from the nits.
These treatments can sometimes 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.
- Isopropyl myristate/cyclomethicone (Resultz) is approved for use in Canada, but it should only be used in children 4 years of age and older. It dehydrates the lice and they die. Apply to a dry scalp and rinse with warm water after 10 minutes. Repeat after 1 week.
- Silicone oil dimeticone (NYDA) is effective against live lice, nymphs and nits. It is not recommended for children under 2 years old. A second treatment is recommended after 8 to 10 days.
- Benzyl alcohol lotion 5% (Ulesfia) is effective against live lice but a second treatment is recommended after 9 days.
These products are usually more expensive than insecticides. It is not known for sure whether they work better.
- Some people suggest 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 little evidence that wet combing (removing lice by combing wet hair with a fine-tooth comb) works all on its own.
- There is no evidence that products such as tea tree oil or aromatherapy work to treat head lice.
- Ivermectin is a drug that can be taken by mouth or used as a cream, but it is not approved for use in Canada.
- Never use gasoline or kerosene. These products can be extremely dangerous.
Do I need to disinfect the house if someone has head lice?
Because head lice don’t live long off the scalp, there is no need for extra cleaning.
However, you do need to get rid of lice or nits from items that touch the head such as hats, pillowcases, combs and brushes:
- Wash items in hot water and dry them in a hot dryer for at least 15 min; or
- Store the items in an airtight plastic bag for 2 weeks. Use a Ziploc-type bag that is airtight. A regular shopping bag often has little holes.
Should children with head lice stay home from school?
Children with head lice should be treated and then attend school or child care as usual. ‘No-nit’ policies that keep children with head lice or nits after treatment away from school are not necessary because:
- Head lice are common among young children. Many days of school would be missed if children had to stay home.
- People are often wrong when they think a child has head lice. It would be unfortunate to see children missing school when they don’t really have lice.
- Making children stay at home will not get rid of head lice. Often, other children in the class have lice but don’t have any symptoms. Without treatment, they will continue to spread lice.
- Head lice don’t spread disease. They are a nuisance and unpleasant, but they are not dangerous.
How to prevent head lice?
Teach your child to avoid head-to-head contact. Children should not share combs, hairbrushes, tuques, hats or hair accessories.
More information from the CPS:
Reviewed by the following CPS committees:
- Infectious Diseases and Immunization Committee
Last Updated: September 2016