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Head Lice

Head Lice

5 April 2017

Causative agent

Head lice, Pediculus humanus capitis, are tiny parasites that only live on the human head. They are usually found on the hair, most often around the hairline behind the ears or near the neck and occasionally on the eyebrows or beard.

Clinical features

The most common symptom is tickling and itchy sensation on the scalp. Excessive scratching may cause bleeding or sores of the scalp, increasing the risk of skin infection.

Under careful inspection, eggs of head lice can be found near the root of the hair. They are different from dandruff. Eggs are white, yellow, brown or grey in colour; usually shiny, oval in shape and firmly attached to the hair shaft, while dandruff are dull, flaky and loose enough to fall off easily.

Mode of transmission

The lice move by crawling; they cannot jump or fly from one hair to another. The main mode of transmission is through direct head-to-head contact with infested people and less commonly through sharing of personal items such as combs, hats or hair accessories. Anyone may catch head lice. However, young children are of higher risk because they often come into close contact with one another while playing.

Incubation period

The life cycle of head lice goes through 3 stages: the eggs, the nymphs and the adults. The eggs hatch in 7 - 10 days; the nymphs take 7 - 12 days to become adults, which can reproduce in huge numbers. Both nymphs and adults feed on human blood. Adult lice can live up to 30 days and usually die within 2 days if they fall off from the human body.


  • If you suspect head lice, seek medical advice immediately.
  • Apply medicated lotion or shampoo according to doctor’s prescription to kill the lice.
  • Use a fine-toothed comb to remove the eggs. Remember to discard the eggs properly.
  • Wash personal items such as brushes, combs, hats and bed linen with hot water and detergent thoroughly.
  • Screen household contacts and close contacts of infested people for head lice and treat them accordingly.


  • Avoid close contact with infested people, especially direct head-to-head contact.
  • Do not share personal items such as combs, hats, hair accessories, towels or pillows.
  • Maintain good personal hygiene. Wash hair regularly and thoroughly, and wash bed linen and clothing frequently.
  • Check hair regularly for signs of head lice infestation.