What are head lice?
Also called Pediculus
humanus capitis (peh-DICK-you-lus HUE-man-us CAP-ih-TUS), head lice
are parasitic insects found on the heads of people. Having head lice is
very common; as many as 6-12 million people worldwide get head lice
each year.
Who is at risk for getting head lice?
Anyone who comes in close
contact with someone who already has head lice, contaminated clothing, and
other belongings. Preschool and elementary-age children, 3-10, and their
families are infested most often. Girls get head lice more often than
boys, women more than men. In the United States, African-Americans rarely
get head lice.
What do head lice look like?
There are three forms of
lice: the nit, the nymph, and the adult.
Nit:
Nits are head lice eggs. They are
hard to see and are often confused for dandruff or hair spray droplets.
Nits are found firmly attached to the hair shaft. They are oval and
usually yellow to white. Nits take about 1 week to
hatch.
Nymph:
The nit hatches
into a baby louse called a nymph. It looks like an adult head louse, but
is smaller. Nymphs mature into adults about 7 days after hatching. To
live, the nymph must feed on blood.
Adult:
The adult louse
is about the size of a sesame seed, has six legs, and is tan to
greyish-white. In persons with dark hair, the adult louse will look
darker. Females lay nits; they are usually larger than males. Adult
lice can live up to 30 days on a person's head. To live, adult lice need
to feed on blood. If the louse falls off a person, it dies within 2
days.
Where are head lice most
commonly found?
On the scalp behind the
ears and near the neckline at the back of the neck. Head lice hold on to
hair with hook-like claws found at the end of each of their six legs. Head
lice are rarely found on the body, eyelashes, or
eyebrows.
What are the signs and symptoms
of head lice infestation?
- Tickling feeling of
something moving in the hair.
- Itching, caused by the
an allergic reaction to the bites.
-
Irritability.
- Sores on the head
caused by scratching. These sores can sometimes become
infected.
How did my child get head
lice?
- By contact with an
already infested person. Contact is common during play at school and at
home (slumber parties, sports activities, at camp, on a
playground).
- By wearing infested
clothing, such as hats, scarves, coats, sports uniforms, or hair
ribbons.
- By using infested
combs, brushes, or towels.
- By lying on a bed,
couch, pillow, carpet, or stuffed animal that has recently been in
contact with an infested person.
How is head lice infestation
diagnosed?
By looking closely
through the hair and scalp for nits, nymphs, or adults. Finding a nymph or
adult may be difficult; there are usually few of them and they can move
quickly from searching fingers. If crawling lice are not seen, finding
nits within a 1/4 inch of the scalp confirms that a person is infested and
should be treated. If you only find nits more than 1/4 inch from the
scalp, the infestation is probably an old one and does not need to be
treated. If you are not sure if a person has head lice, the diagnosis
should be made by a health care provider, school nurse, or a professional
from the local health department or agricultural extension
service.
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