Head lice

Head lice



Head lice have infested humans for thousands of years. Infestation with lice is quite often inappropriately considered related to poor hygiene and low socio-economic status. In fact people of all walks of life can get infested with lice. In the US alone, there are over 12 million cases of head lice per year.


Head lice have infested mankind for thousands of years. Nits have been found on the hair of both Egyptian and Peruvian mummies.




Head lice are found worldwide with no strict limitations based upon age, sex, race or socioeconomic class. Children 3-11 years of age have the highest incidence and it is more common in girls, probably due to their predilection for longer hair.


Head lice grip on to hair by their claws and rapidly move from hair to hair. They don't jump or fly but can quickly move from one person to another if in close proximity. By injecting saliva into an infected person's scalp they are able to suck blood which provides their nutrition. This can occur up to five times a day. Itching and irritation results from the louse feeding. Lice lay eggs (nits) on the hair shaft close to the scalp. Here the warmth of the scalp will incubate them. The nits are cemented on to the hair and are carried away from the scalp as the hair grows. They hatch at around 8 days. The empty egg case then turns white and becomes more easily seen.

Clinical features

Skin findings of head lice are limited to the scalp, behind the ears and the nape of the neck. The classic symptom of intense pruritus can vary among patients.

Scratching can cause crusting and scaling on the scalp. Occasionally secondary bacterial infection of the scalp results in small sores on the scalp with tender glands in the neck. Dermatitis can also occur with a heavy infestation of lice. Fortunately head lice are not known to carry any diseases which can affect humans.

It is important to identify the lice (or nits) to make a correct diagnosis. Lice are around 3mm in length and can be seen moving from hair to hair. Unhatched eggs are within a few millimetres of the scalp and have a dark area within the shell while hatched eggs are transparent. Occasionally the eyelashes can become infested.


Pediculicides remain the mainstay of therapy and with all topical preparations, two applications, 1 week apart, are available in order to: 1) kill any nits that survived treatment; 2) better defend against the seemingly growing resistance to most pediculicides; and 3) reduce the risk of reinfestation by means of fomites.

Important points to remember when treating head lice

-       Regularly examine your children's scalps. Look for nits close to the skin, behind and above the ears and on the back of the neck.

-       Treat all members of the family at the same time.

-       Not all eggs are killed with one application of insecticide, therefore a second application is recommended 7 days later.

-       The lice may not be killed immediately and may take a day or so to die.

-       The presence of nits doesn't mean ACTIVE infection. Hatched nits (empty eggshells) will remain attached to the hair shaft until the hair grows out, unless they are actively removed or the hair is cut.

-       Machine-wash all bed linens, clothes, towels in hot water.

-       Items that can't be washed such as soft toys and helmets should be placed in an airtight plastic bags for two weeks.

-       Vacuum pillows, etc.

-       Spray hairbrushes, combs with fly spray


Physical methods

Physical methods of removing nits and lice, often a neglected part of treatment, can be effective on their own. They are however more reliable used in conjunction with insecticide treatments. Eggs are cemented strongly to the hair shaft and simple washing usually doesn't remove them. Nit combs are the most effective way of physically removing the nits. Metal combs are much more effective than plastic. Electrical combs designed to 'zap' lice on the hair shaft are not effective.

-       Using a nit comb is easiest when the hair is wet. Combing may be easier if a conditioner is applied first. It is best done after treating with insecticides.

-       Use a good light.

-       Work through the hair in sections and comb down the hair shaft towards the scalp to try and remove the stubborn nits.

-       It may be easier if this is done while the child is kept occupied (for example watching television).

-       Repeat the combing at least twice more on consecutive nights if possible and then weekly.