There are three types of lice affecting humans — head lice, body lice and crab lice. Lice can lay eggs on hair shafts or on the seams of clothing, depending on the type of louse involved. Lice eggs have a distinctive appearance but, because an infestation sometimes does not produce any symptoms, careful examination of hair or clothes is necessary to spot them. They are tiny; can be brown or white, depending on whether they're live, dead or hatched; and are likely to have one end missing if the egg has hatched. The live eggs can be popped, though dead or hatched shells are too dry to pop.
Children often become infested with head lice through coming into close contact with previously infested children. The main symptom of head lice, when symptoms are present, is itchiness. Adults can become infested with crab lice or body lice through close personal contact or bad hygiene, and the nits in these cases are laid on the pubic hair or on seams of clothing, respectively.
Lice go through three stages of development, changing from lice eggs into nymphs that then grow into adult lice. A female louse lives for about 30 days on a host and lays about 90 eggs in this time. She lays about three eggs a day, and they take a week to hatch. The nymphs molt, or shed their skin, several times over eight or nine days prior to becoming adults. Female adult lice are up to 1/8 inch (3.18 mm) long, and males are smaller.
Lice eggs can be in one of three states — live, dead or hatched. Live eggs are brown in color and are attached via a cement-like substance to the hair shaft. The egg itself is cylindrical in appearance. A live egg can be popped if squeezed by the fingers.
A hatched egg is white in color and is missing one end of the egg where the louse emerged. A hatched egg can be crumpled easily. A dead egg is brown, has a dead louse embryo inside and has the top of the egg intact. A dead egg also can be crumpled easily, unlike a live egg.
Head lice are found on head hair, especially behind the ears. Crab lice are found in the pubic area or occasionally in armpit hair, a beard or mustache. Crab lice lay their eggs on hair shafts the same as head lice, though they more commonly use pubic hair shafts than scalp hair shafts.
Body lice lay their eggs in seams of clothing and occasionally on body hairs. Body lice live on clothing and move to the body when they wish to feed. Body lice eggs can be removed from clothing through regular washing.
Head lice eggs can be similar to dandruff in appearance. Dandruff is easily removed through combing, but lice eggs are cemented to the hair and are harder to dislodge. Lice can be removed from hair through regular combing with a fine-tooth comb or through using an insecticidal shampoo, cream or lotion available from chemists. If all else fails, lice eggs can be removed by cutting the hair to which they are attached.