What are the aims of this leaflet?

This leaflet has been written to help you understand more about head lice. It tells you what head lice are, how to treat them, and where you can find out more about them.

What are head lice?

Head lice are very common. They are small grey-brown insects that grow up to 3mm long. They cannot fly or jump; neither can they burrow into the scalp. They can affect anyone with long or short hair, no matter how clean the hair is.

How are head lice acquired?

Head lice are usually picked up by head-to-head contact; it takes about 30 seconds for a single louse to transfer from one scalp to another. Less often, sharing hats, combs or pillows can spread them. Head lice live only on humans and die in a day or two away from the human scalp. They cannot be caught from animals.

Head lice can affect anyone, but are:

• Most common in children between the ages of 4 and 11.
• More common in girls than boys.

Are head lice infestations hereditary?

No, though several members of a family may have them at the same time.

What are the symptoms of head lice infestation?

Head lice have to feed on human blood several times a day to survive, and their bites, saliva and faeces often make the scalp itchy. Some people may be unaware they have head lice as they do not experience any symptoms. This lack of itching does not mean that lice are not present, and the only way to be sure is by taking a careful look at the scalp.

Repeated scratching of the scalp may cause an additional bacterial infection. In this case the scalp may also feel sore, crusty, and result in a raised temperature and feeling generally unwell. If this occurs, you should contact a healthcare adviser in case antibiotic treatment is required.

What does a lice-infested scalp look like?

An affected scalp carries a mixture of the following:

• Eggs containing developing lice – firmly stuck to the hair shafts near to the scalp. They are grey or brown and the size of a pin head. They take 7-10 days to hatch. New lice will then lay more eggs 7-10 days after they hatch.
• Empty egg cases (nits) are white and shiny, and also firmly stuck to the hairs, but further away from the scalp surface.
• Immature lice are smaller than adult lice.
• An average of 10 adult lice may be seen at one time, though some scalps carry many more.
• Lice droppings – most easily seen as dark specks on pillows or clothing.

These may be difficult to spot. The sides and back of the scalp are usually more heavily infested.

Other features of a head lice infestation can include:

• Scratch marks.
• A sticky, crusty or weeping scalp. This is usually a sign of an additional bacterial infection (impetigo).
• Small itchy bumps around the hair line particularly on the back of the neck.
• Enlarged glands, which will feel like firm lumps beneath the skin in the neck.

How are head lice diagnosed?

Head lice should be considered in anyone who has an itchy scalp, or who has repeated skin infections on or around their scalp. There are many other causes of scalp itching that can be mistaken for head lice. These include folliculitis, psoriasis, eczema and dandruff, but they do not have the features mentioned above. Sometimes excess application of a styling product dried onto the hairs can look rather like nits, but this will wash off and slide easily along the hair, whereas eggs are fixed firmly to hair.

The diagnosis is made by identifying active head lice through careful examination of the scalp. Repeated combing of wet and dry hair using a fine-toothed nit comb can be used to identify the features listed above. A bright light and magnifying glass can be helpful to aid this. No special tests are needed, and combing can be done at home.

Can a head lice infestation be cured?

Yes, but this is not always easy as some lice are now resistant to the insecticides used to treat them, and repeated infestations are common.

How can a head lice infestation be treated?

Treatment is needed only when an active louse infestation is present; as shown by the presence of living and moving lice. Neither itching by itself, nor evidence of an old infestation (only empty egg cases), is a reason for starting treatment.

Once a decision to treat has been made, there are three main choices:

1. A physical insecticide

A physical insecticide works by physically coating the surfaces of head lice and suffocating them, so resistance is unlikely to develop.

Depending on the product, this may be in the form of a lotion, spray, or gel. Commonly used active ingredients include dimeticone, isopropyl myristrate with cyclomethicone and isopropyl alcohol with isopropyl alcohol.

2. A chemical insecticide

A chemical insecticide, such as Malathion 0.5% aqueous liquid, poisons the head lice by chemical means. Resistance has been reported.

3. Wet combing with nit combs Lubricating the hair with a conditioner or a product containing dimeticone makes the procedure easier, particularly for curly hair. Using an ordinary wide-toothed comb first can help straighten and untangle the hair. A fine-toothed comb (detection comb) can then be used. All of the hair should be combed, from the roots to the tips, with the comb cleaned after each pass to remove the lice and eggs. This is best done by wiping on clean white paper, or cloth, or by running under water. Working through the hair methodically a section at a time reduces the risk of missing areas. Repeating the wet combing on days 1, 5, 9 and 13 will help catch any newly hatched head lice. Further information on wet combing is available on the Community Hygiene Concern Other members of the household should also be checked

Herbal and essential oil preparations are not recommended as there is insufficient research to support their use.

In general, when using the above treatments, the following points should be kept in mind:

• Follow the product information leaflet strictly when applying the treatment and ensure it is repeated at the instructed intervals.
• Insecticides should be applied to dry hair, to all areas of scalp, and to all hairs from their roots to tips.
• Head lice shampoos are less effective than lotions, as they are diluted too much and have an insufficient contact time to kill eggs.
• Wet combing or dimeticone 4% lotion is generally recommended as the first line treatment for those who are pregnant or breastfeeding, young children aged 6 months to 2 years, and people with asthma or eczema.

When lice do not clear

There are several reasons why symptoms may not improve after treatment:

• The diagnosis of head lice infestation may have been incorrect.
• You may not have followed the treatment instructions correctly or repeated the treatment at the correct intervals.
• The lice may have been resistant to the chosen treatment.
• You may have picked up a new infestation immediately after the treatment finished. Consider assessing all close contacts and household members to identify sources of re-infestation.

Self-care (What can I do?)

• After the treatment is complete you should check every week, for a month, to ensure the infestation has cleared.
• Make sure that everyone who has been in contact with an affected person is examined to ensure that they have not got head lice too; this especially applies to members of the same household and to close school friends.
• All affected members of the household should begin treatment on the same day.
• The combs and brushes of a person with head lice should be washed in hot water daily.

There is no need to keep children with head lice away from school as long as the advice given above is followed.

Can head lice infestation be prevented?

It is not possible to prevent headlice infestation. Children of primary school age should be examined regularly at home using a nit comb to identify infestation early as prompt treatment helps prevent further spread.

Do not use chemicals regularly to prevent an infestation occurring; this simply encourages the emergence of resistant strains of lice.

Where can I get more information about head lice infestations?

Web links to other relevant sources:

www.medinfo.co.uk/conditions/headline.html

www.cdc.gov/parasites/lice/head/index.html

www.nhs.uk/conditions/Head-lice/Pages/Introduction.aspx

https://patient.info/news-and-features/how-to-check-your-child-for-head-lice-and-nits

www.chc.org

https://cks.nice.org.uk/head-lice#!scenario

Jargon Buster:
https://www.skinhealthinfo.org.uk/support-resources/jargon-buster/

The British Skin Foundation fund vital research into all skin diseases. To find out how you can help, please visit the British Skin Foundation website.

Please note that the British Association of Dermatologists (BAD) provides web links to additional resources to help people access a range of information about their treatment or skin condition. The views expressed in these external resources may not be shared by the BAD or its members. The BAD has no control of and does not endorse the content of external links.

This leaflet aims to provide accurate information about the subject and is a consensus of the views held by representatives of the British Association of Dermatologists: individual patient circumstances may differ, which might alter both the advice and course of therapy given to you by your doctor. 

This leaflet has been assessed for readability by the British Association of Dermatologists’ Patient Information Lay Review Panel 

BRITISH ASSOCIATION OF DERMATOLOGISTS
PATIENT INFORMATION LEAFLET
PRODUCED | FEBRUARY 2008
UPDATED | JANUARY 2011, FEBRUARY 2014, MAY 2017, OCTOBER 2020, APRIL 2024
NEXT REVIEW DATE | APRIL 2027