About 10-12 million people, mainly children, are treated annually for head lice in the US. Girls are about 3-4 times more likely to be infested than boys. Children between 4 to 13 years of age are the most frequently infested group.
What is Pediculosis?
Pediculosis is an infestation of the hairy parts of the body or clothing with the eggs, larvae or adults of lice. Head lice are wingless insects spending their life on human scalp and feeding exclusively on human blood. The term "nit" refers to either a louse egg or a louse nymph.
What does head lice look like?
Cick on head lice pictures to zoom.
Lice Eggs:
In cool climates, eggs are generally laid within a half inch of the scalp surface. The female secretes glue, made of proteins similar to hair keratin,for each egg to stick. This glue covers the hair shaft and the entire egg except for the operculum, a cap through which the embryo breathes. Typically, hatching time is 6 to 9 days, which is why the FDA advises a second treatment 8 days after the first.
How do head lice feed?
Lice feed from blood. To feed, lice bite the scalp 4 to 5 times daily and inject saliva which prevents the blood from clotting. Bloodsucking may continue for a long period with no intervention.
Position on host:
Although any part of the scalp may be "colonized", lice favor the nape of the neck and the area behind the ears, where the eggs are usually laid.
How does head lice migrate?
Lice are wingless and they cannot jump. They move by using their claw-like legs to transfer from hair to hair. Head-to-head contact is the most common route for lice transmission.
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