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Lice: head lice

What is the cause?

Pediculus humanus capitis is the head louse. This small insect, which lives on human hair, sucks blood from the skin of the scalp. The female louse lays eggs (or 'nits'), which are glued to the hairs and hatch within 6 days, mature into adults in about 10 days and live for about a month.

How is it spread?

Had lice spread from person to person by direct contact, such as sitting and working very close to each other. They can spread by sharing combs, brushes and headwear, especially within the family. Children are the ones usually affected, but people of all ages and from all walks of life can be infested. It is more common in overcrowded living conditions.

What are the symptoms?

Head lice may cause itching of the scalp, but often there are no symptoms. The white spots can be mistaken for dandruff.

How is it diagnosed?

The finding of lice or nits on the head is the only way to diagnose infestation. The nits are seen as small, whitish flecks securely attached to the base of the hairs, especially behind the ears and on the forehead. Unlike dandruff, they cannot be brushed off.

What is the treatment?

Topical medication

The best treatment is 0.5 per cent malathion (maldison), which is effective and kills both the lice and eggs. Synthetic pyrethrins are also useful, but gamma benzene hexachloride is less effective and does not kill the eggs. Both lotions and shampoos of maldison are acceptable, although lotions are more effective. Follow the instructions on the bottle carefully. The hair does not have to be cut short if the medication is properly and thoroughly applied.

Where should it be applied?

Apply to the hair of the head only.

How often?

Apply once a week for 2 weeks. One application of maldison may be sufficient to clear the lice.

Combing

The eggs can be removed after treatment by combing with a fine-tooth metal comb while the hair is wet.

Note

• Head lice are not associated with lack of cleanliness.
• Ordinary hair washing cannot prevent or cure it.
• If one member of the family has it, all members must be treated whether or not lice or nits can be detected.
• The source of head lice is the home, not the school.
• As lice cannot survive for long off the body, there is no need to treat clothing, pillows or household furniture or carpets.
• Although regulations vary from state to state, exclusion from school should not be necessary after proper treatment.
• All anti-louse preparations are toxic, but they are safe if the special head louse lotions are used according to the directions. Keep all preparations out of the eyes and out of the reach of children
• Under no circumstances should garden formulations of the malathion insecticide be used.

Copyright 1995: John Murtagh, Professor of General Practice
Monash University, Melbourne, Australia

See also Department of Human Services Australia site  http://www.dhs.vic.gov.au/phd/9908014/index.htm