Head lice, Pediculus humanus capitis, are tiny parasites (up to 3mm long) 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.
The most common symptom is itching and tickling sensation on the scalp. Excessive scratching may cause bleeding or sores on 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 usually white or yellow in colour, oval in shape and firmly attached to hair shafts; while dandruff is 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 head-to-head contact with an infested person, 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.
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 but usually die within 2 days once they fall off from the human body.