Head lice - Diagnosis 

Detecting head lice 

Head lice and school

There is no need for children with head lice to be kept off school.

They will probably have had the infestation for several weeks, so keeping them away from school is unlikely to affect transmission.

It is difficult to identify head lice simply by inspecting your child's head. Detection combing is a more reliable method.

Detection combing

Detection combing can be carried out on dry or wet hair. Less preparation is needed to comb dry hair, but wet combing is more accurate because lice remain motionless when wet.

You will need a special fine-toothed detection comb available from pharmacies. The comb has a tooth spacing of less than 0.3mm to trap the smallest lice.

Nit combs are not suitable for louse detection as the teeth are too close together. Lice can get trapped between the teeth and remain unseen.

Wet detection combing

Follow the steps below for wet detection combing.

  • Wash hair using ordinary shampoo and apply plenty of conditioner. Use a wide-toothed comb to straighten and untangle the hair.
  • Once the comb moves freely through the hair without dragging, switch to the louse detection comb. Make sure the teeth of the comb slot into the hair at the roots with the bevel-edge of the teeth lightly touching the scalp.
  • Draw the comb down to the ends of the hair with every stroke, and check the comb for lice.
  • Remove lice by wiping or rinsing the comb.
  • Work methodically through the hair, section by section, so that the whole head of hair is combed through.
  • Rinse out the conditioner and repeat the combing procedure in the wet hair.

Dry detection combing

Follow the steps below for dry detection combing:

  • Use an ordinary comb to straighten and untangle the hair.
  • Once the comb moves freely through the hair without dragging, switch to the louse detection comb. Comb the hair from the scalp to the ends, combing each section of hair three or four times before moving on to the next section.
  • Look for lice as the comb is drawn through the hair. If you see a louse, trap it against the face of the comb with your thumb. This helps to avoid the louse being repelled by static electricity as the comb is removed from the hair.
  • Continue combing the hair, section by section, until the whole head has been combed through.

You can be confident of an active infestation if a live louse is found in the hair.  If you are still unsure, you can attach any lice you find to sticky tape and take it to your GP or practice nurse for confirmation.

Checking the rest of the family

If you discover head lice in your child's hair, you should check the rest of the family, alert close friends and inform your child's school.

Treatment should only be carried out after live head lice have been found. Do not treat hair "just in case". However, once confirmed, take immediate steps to treat head lice.

Read more about treating head lice.

Page last reviewed: 27/06/2012

Next review due: 27/06/2014


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Just hearing that other people have head lice can make you start itching.

Simply having an itchy head does not mean you have head lice. A diagnosis can only be made if a live head louse is found.

Itching may continue for days or weeks, even after all head lice have been removed. In some cases, itching starts months after a person has an infestation.

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Your child will be offered a range of health checks and vaccinations at school. Find out why they're so important.