Headlice and nits

Health and Nutrition > Diseases > L Written by Dr Gillian Rice, GP

What are lice?

The head louse is a tiny greyish-brown insect, about 2.5mm long.

Head lice cling to hair and are usually found on the scalp. They live on blood from the host, which they get by biting through the scalp.

Adult lice mate. The female then lays eggs that are firmly attached to hair close to the scalp and can be very difficult to remove.

After seven or eight days the baby louse hatches out of the egg, leaving a shiny white empty eggshell (nit), which may be found anywhere along a strand of hair.

What causes an infection of head lice?

Infection with head lice is a very common problem in the UK, especially among school children.

Lice pass from one person to another during direct head-to-head contact. This is because lice cannot jump, fly or hop; they can only transfer to another head by walking along strands of hair.

Children whispering secrets at school or families enjoying a cuddle at home provide head lice with the ideal opportunity to travel from one head to the next.

Lice seen on pillows, hats or chair backs are not capable of transferring to another person.

The belief that head lice are associated with poor hygiene is common but misfounded. Lice are equally likely to be found on clean or dirty hair.

Head lice should be seen as nothing more than an unpleasant inconvenience that can be treated.

What symptoms do head lice cause?

Bites from head lice can cause intense itching and irritation on the scalp, but these symptoms may not appear until at least two months after the lice move in. A rash at the nape of the neck may also develop.

What is the best way of looking for head lice?

You can part the hair and look for nits, but the lice will move quickly into hiding.

The best way to search for head lice and nits is to buy a specially designed detection (nit) comb from a pharmacy. This is a fine-toothed plastic comb with spacing of less than 0.3mm.

You can check for lice on dry or wet hair.

Head lice tip To help detection, get your child to lean over a sheet of light coloured paper or cloth as you comb the hair.

Both live lice and eggshells may drop onto the paper.

What if I find lice?

Check every other member of the family, including any adults who have close contact with the child.

You can work out when the lice first moved in by judging how many centimetres from the scalp you find the nits. Hair grows at about 1cm a month; so a nit 2cm from the scalp was laid about two months ago.

It's also helpful to tell the school and parents of any other child who may have had head-to-head contact with your child, so that other children can be checked for lice.

How are head lice treated?

The three main treatments for head lice are listed below, but no method is 100 per cent effective.

You should only start chemical treatment if you find a live louse on your child's head. If you only find the hatched and empty eggshells (nits), these may be the sign of a previous batch of lice that have already been eradicated.

Insecticides

Good advice Current clinical advice is not to recommend shampoo and mousse forms of insecticides because their short contact time is not enough to be effective.

Did you know?

Insecticides can't prevent your child getting head lice, so don't use 'just in case'.

They should only be used when a live louse is found.

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