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Head lice
What are head lice?
Head lice (Pediculus humanus capitis) are tiny wingless insects about two
millimetres long which live on the scalp and neck of humans. When an infestation
occurs there may be up to 12 adult lice on the scalp at any one time. They feed from
human blood and must eat at least twice a day; they cannot survive for more than
one day at room temperature off a human body. A female louse can lay eggs at the
rate of about six per night up to a total of 100. The yellow-white eggs, called nits, are
stuck to the hair close to the scalp. As the hair grows, so the nits (or their empty
shells) are carried away from the scalp and are more easily visible. Nits can often be
mistaken for dandruff, flakes of dry skin or other small items caught in the hair.
What do head lice and nits look like?
We have several pictures that we have gathered.
Enlarged Pictures of head lice
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Enlarged Pictures of Nits (eggs)
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What causes head lice and who is at risk?
Head lice cannot fly and they cannot jump
from one person to the next; they are not
transmitted from household pets or other
animals. Instead, when they are caught, it
is usually through head-to-head contact
or by sharing hair accessories, such as
hair-brushes, combs, hats or even by
putting these items on top of each other.
Head lice can also survive for short times
on bedding and furniture. Children are
particularly prone to infestation with head
lice as they often have close contact with
each other at school or when playing.
There is no link between the presence of
head lice and a lack of hygiene or
susceptibility to infection.
What are the common symptoms and complications of head lice?
Often the first sign of infestation is an
itchy head or neck. The saliva of head lice
is irritating on the skin, and itching is
often worse behind the ears or at the
back of the neck. However, head lice do
not always cause itching. In some
developing countries, human head lice
have been blamed for passing rare
diseases from person to person. In the
United States and other devolped nations, lice do not usually cause direct harm
to an affected person but the persistent
irritation and itching can disturb
concentration and disrupt sleep. When
trying to eradicate the lice, care should be
taken not to overuse potentially
hazardous medicines.
How do I recognize head lice?
The only way of confirming an infection
with head lice is by seeing either the adult
lice or their eggs in the hair. The lice tend
to stay close to the scalp and move away
from direct light, but the nits are stuck to
the hair shafts. In searching for nits and/or
lice, the following are important:
- clean, tangle-free hair,
- bright light, especially natural light,
- use of a fine comb - special 'nit-picking' combs are available at your pharmacy (use
plastic rather than metal ones and start combing at the roots of the hair),
- using a magnifying glass may be helpful.
Nits may be distinguished from, for
example, dandruff, by trying to move
them off the hair shaft. As they have been
firmly attached by the parent lice, nits are
not easily removed. Even after treatment,
empty nit shells may remain stuck to the
hair. The shells tend to look whiter and
more shiny, and to be more than 0 to 1 inch away from the scalp.
They are not a sign of re-infestation.
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