In winter children are more likely to be playing together indoors. And all those heads close together can lead to sharing more than play time. If your child has come home with an itchy head - could it be head lice? Nina Goad of the British Skin Foundation answers your questions about how to deal with head lice.

Head lice are small parasitic insects that live on human scalps and cause great annoyance to children and parents alike. Despite popular perception, head lice are very common and can affect everyone – they do not mean that a child is dirty.

Head lice cannot fly, jump, or burrow into the scalp, but their six legs are perfectly adapted for clinging onto hair. Children usually pick them up through head-to-head contact, which makes them common among children who have close contact in the playground. In some cases, lice may be spread through shared hats, combs or pillows, but they cannot be caught from animals.

Head lice have to feed on tiny amounts of human blood several times a day to survive, and their bites, saliva and faeces often make the scalp itchy.

They can affect anyone – rich or poor, well-washed or not – but are...

• Most common between the ages of 4 and 11. 
• More common in girls than boys. 
• Most often found at the start of the school year.

An affected scalp carries a mixture of the following:

• Eggs containing developing lice – firmly stuck to the hair shafts near to the scalp.
• Empty egg cases – also firmly stuck to the hairs, but lying further from the scalp surface. 
• A number of immature lice. 
• An average of 10 grey, adult lice (approximately 3-4mm long) - some scalps may carry many more.
• Lice droppings – most easily seen as dark specks on pillows or collars.

How to deal with head lice

Treatment is needed only when an active louse infestation is present – as shown by the presence of living and moving lice, or of living eggs. Neither itching alone, nor evidence of an old infestation (i.e. empty egg cases), is an adequate reason to start treatment.

Once a decision to treat has been made, there are two main choices: the use of chemicals (pediculicides) that kill lice, or physically removing the lice and their eggs through repeated combing.

Your doctor or pharmacist will be able to advise you on a chemical treatment and you should follow the instructions carefully. You will most likely need to apply the treatment to all areas of the scalp, and to all of the hairs, from root to tip. Pediculicides come in a variety of formulations, including shampoos and lotions.

Regular daily combing with a louse or nit comb can clear lice infestations. A good light and magnifying glass are needed and the combing has to go on until no living lice have been found for two weeks. Clean the comb regularly to remove the lice and thoroughly lubricate hair with a conditioner.

After treatment

• Once the treatment is over, you should check every week to ensure the lice have been cleared. 
• Examine family and close friends to ensure that they remain clear of head lice. 
• Wash and hot-dry pillowcases, sheets, and nightclothes that might pass lice on to other members of the family. The combs and brushes of an infested person should be washed in hot water daily. 
• It is not a good idea to use pediculicides after the treatment to prevent infestation taking place – in fact this encourages the emergence of resistant strains.

If the treatment fails

There are several reasons why treatment may not work. For example, the louse diagnosis may have been wrong in the first place, you may not have followed the treatment instructions correctly, the lice may have been resistant to the pediculicide chosen, or your child may have picked up a new infestation.