Head Lice (Pediculosis)

What are lice?

Lice are tiny insects. In fact, they are considered parasites because they feed on human blood, much like mosquitoes. Lice, which reproduce very quickly, live at the surface of the skin, clinging to the host's hair shaft with their claws. Having lice is not a sign of poor hygiene. You can get rid of lice as long as you follow certain steps.

What do they look like?

Lice look like dandruff flakes or small, grey-coloured grains. However, because they are so tiny and move around very quickly, spotting adult lice is quite uncommon. What we usually see are lice eggs called "nits". A glue secreted by the lice allows the nits to remain attached to the hair, most often close to the scalp. Nits are pearl-grey in colour, are shaped like a tear and measure less than one millimetre (between the size of a pinhead and a sesame seed).

The primary symptom of a lice infestation is an itchy scalp, which may be more pronounced during the first 3 hours of sleep. The itching is caused by an allergic reaction due to repeated lice bites. It may take up to 4 to 6 weeks before itching develops and some people will not experience any symptoms.

If an infestation is suspected, it is very important that it be confirmed before starting treatment. Lice treatments must never be used as a preventive measure. Treatment should only be used when live lice are found.

Nits and head lice

Where are they found and how go we get them?

Lice spread through direct contact with an infested person or, less often, by indirect contact with certain infested objects. Contrary to popular belief, lice cannot jump or fly. It is also important to note that lice do not live on pets.

Head lice are found in hair, behind the ears and on the nape of the neck (and can also be found on beards and eyebrows). They mainly spread through close head-to-head contact such as hugging or embracing, for example. Keeping long hair tied back is a simple and effective way to prevent lice from spreading. Although less likely, sharing personal items such as baseball caps, combs, and clothing can also contribute to spreading lice. However, head lice cannot live without a human host for more than three days.


Treatment involves the use of specially formulated head lice products that contain an insecticide. These products usually consist of shampoos, conditioners or sprays that are applied to the site of the infestation. Speak to your pharmacist, as he or she will be able to recommend a product that is safe and effective. In order to completely and successfully eradicate head lice, you must carefully follow the directions for use, as well as the pharmacist's recommendations. If an infestation is suspected, it is important that anyone who may have come into contact with the person in question be notified, so that treatment may be administered as soon as possible, but only if lice are confirmed.

When a child has lice, it is important to notify the school or daycare so parents can check and monitor their children. Contrary to popular belief, children do not need to stay home for any extended period of time. In fact, they can go back to school after the first treatment has been applied.

Treatment may fail and, in most cases, there is a valid reason. Here are the most common factors that lead to treatment failure:

  • Treatment was applied to dry hair instead of wet hair or vice versa (depending on which product is used)
  • Treatment was not left on the hair for the recommended time
  • Treatment was not repeated within the recommended timeframe
  • The lice are resistant to the treatment in question

If the eyebrows are infested, apply a thick layer of Vaseline at least twice a day, for about one week.

In addition to treatment

Visually inspecting the hair under a good light source is important. Remove nits after each application, then 2, 11 and 17 days after the first treatment. A thorough inspection takes between 10 and 30 minutes. Here are the steps to follow:

  1. Wet hair with warm water and towel dry.
  2. Use a conditioner. Conditioner may make it easier to see the lice since it slows them down and makes the hair easier to work with. Conditioners however, should not be used after a permethrin treatment.
  3. Use a fine-toothed comb with parallel-sided teeth. The space between the teeth should be no more than 0.2 to 0.3 mm. The comb should be made of metal or ABS plastic (acrylonitrile butadiene styrene) and light-coloured to make it easier to see the lice and nits.
    • Short hair: To remove nits, start at the roots and comb towards the ends of the hair.
    • Long hair: Take a strand that is 2 to 3 cm wide and separate using disposable clips or elastics. Then, run the comb through the hair starting at the roots and making your way towards the ends.
  4. Take a close look at the teeth of the comb after each stroke and, using a paper towel, remove lice from the comb.
  5. If the comb is not enough to remove the nits, tweezers or fingernails can be used to remove them.

To reduce the risk of reinfestation, the following measures are recommended:

  • Soak combs, brushes and hair accessories in very hot water (65°C or 150 °F) or in a recommended lice-killing product, undiluted, for 5 to 10 minutes.
  • Wash clothing, hats, scarves, towels, bedding, etc. in hot water and dry on the hot cycle (for 20 minutes). Dry cleaning is also effective. Place items that cannot be washed in a hermetically sealed plastic bag for 10 days to suffocate the lice.
  • Vacuum pillows, mattresses, carpets, upholstered furniture, stuffed toys, etc. Then, dispose of the vacuum bag.

Common home remedies such as mayonnaise, olive oil and margarine are not shown to be effective. They are not recommended at this time.

Avoiding close contact, such as hugging individuals who are infested, is one of the best measures you can take to protect yourself from contracting lice. It is also important to teach children that they should not share combs, hats and scarves.

For more information:

Canadian Paediatric Society www.cps.ca

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