The Facts of Lice
Head lice are small wingless insects. They look like
walking, light grey sesame seeds, and have six pincer-like
Head lice infest people's hair and suck blood from their
Anyone can get head lice but head lice most often infest
school children. Because they are small and grab tightly
onto hairs, head lice are hard to see. "Nits" (their eggs)
are easier to see. Female lice glue the nits directly onto
the hair shaft next to the scalp. Nits are found anywhere on
the head, most often at the nape of the neck and behind the
ears, but also in eyebrows and eyelashes.
Head lice do not transmit any diseases but they often
cause itching and discomfort.
The best and most effective way to find head lice is by
"wet combing." Wet combing involves washing the hair and
applying conditioner, then combing through with an ordinary
comb to remove tangles. A fine tooth detection comb is then
pulled downwards through the hair, a section at a time,
keeping the comb close to the scalp. The comb is checked for
lice after each section.
If head lice are found, other family members and
classmates should be checked. Checks should be continued
following any scalp treatment to ensure that it has been
effective and to detect any reinfestation.
(Image credit: CDC)
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, which are usually larger than the males, lay eggs.
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.
Adult louse claws
(Photo credit: CDC)
They are 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.
Illustration of egg on a hair shaft
(Image credit: CDC)
Egg/Nit: Nits are head lice eggs. They are very
small, about the size of a knot in thread, hard to see, and are
often confused for dandruff or hair spray droplets. Nits are
laid by the adult female at the base of the hair shaft nearest
the scalp. They are firmly attached to the hair shaft. They are
oval and usually yellow to white. Nits take about 1 week to
hatch. Eggs that are likely to hatch are usually located within
1/4 inch of the scalp.
(Photo credit: CDC)
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.
The most important step in treating a head lice infestation
is to treat the person and other family members with head lice
with medication to kill the lice. Wash clothing and bedding worn
or used by the infested person in the 2-day period just before
treatment is started.
Treat the infested person: Requires
using an over-the-counter (OTC) or prescription medication.
Follow these treatment steps:
- Before applying treatment, remove all clothing from the
- Apply lice medicine, also called pediculicide (peh-DICK-you-luh-side),
according to label instructions. If your child has extra
long hair (longer than shoulder length), you may need to use
a second bottle. Pay special attention to instructions on
the bottle regarding how long the medication should be left
on and whether rinsing the hair is recommended after
Do not use a creme rinse or combination
shampoo/conditioner before using lice medicine. Do not
re-wash hair for 1-2 days after treatment.
- Have the infested person put on clean clothing after
- If a few live lice are still found 8-12 hours after
treatment, but are moving more slowly than before, do not
retreat. Comb dead and remaining live lice out of the hair.
The medicine may take longer to kill lice.
- If, after 8-12 hours of treatment, no dead lice are
found and lice seem as active as before, the medicine may
not be working. See your health care provider for a
different medication; follow treatment directions.
- Nit (head lice egg) combs, often found in lice medicine
packages, should be used to comb nits and lice from the hair
shaft. Many flea combs made for cats and dogs are also
- After treatment, check hair and comb with a nit comb to
remove nits and lice every 2-3 days. Continue to check for
2-3 weeks until you are sure all lice and nits are gone.
- If using OTC pediculicides, retreat in 7-10 days. If
using the prescription drug malathion, retreat in 7-10 days
ONLY if crawling bugs are found.
Click here for instructions on how to use malathion to treat
Treat the household: Head lice do
not survive long if they fall off a person and cannot feed. You
don't need to spend a lot of time or money on housecleaning
activities. Follow these steps to help avoid re-infestation by
lice that have recently fallen off the hair or crawled onto
clothing or furniture.
- To kill lice and nits, machine wash all washable
clothing and bed linens that the infested person wore or
used during the 2 days before treatment. Use the hot water
(130°F) cycle. Dry laundry using high heat for at least 20
- Dry clean clothing that is not washable, (coats, hats,
Store all clothing, stuffed animals, comforters, etc.,
that cannot be washed or dry cleaned into a plastic bag;
seal for 2 weeks.
- Soak combs and brushes for 1 hour in rubbing alcohol,
Lysol*, or wash with soap and hot (130°F) water.
- Vacuum the floor and furniture. The risk of getting
re-infested from a louse that has fallen onto a carpet or
sofa is very small. Don't spend a lot of time on this. Just
vacuum the places where the infested person usually sits or
lays. Do not use fumigant sprays; they can be toxic if
inhaled or absorbed through the skin.
Prevent Reinfestation: Lice are
most commonly spread directly by head-to-head contact and much
less frequently by lice that have crawled onto clothing or
belongings. As a short-term measure to control a head lice
outbreak in a community, school, or camp, you can teach children
to avoid playtime and other activities that are likely to spread
- Avoid head-to-head contact common during play at school
and at home (sports activities, on a playground, slumber
parties, at camp).
- Do not share clothing, such as hats, scarves, coats,
sports uniforms, or hair ribbons.
- Do not share infested combs, brushes, or towels.
- Do not lie on beds, couches, pillows, carpets, or
stuffed animals that have recently been in contact with an
No, although anyone living with an infested person can get
head lice. Check household contacts for lice and nits every 2-3
days. Treat only if crawling lice or nits (eggs) within a 1/4
inch of the scalp are found.
Like germs that are resistant to antibiotics, some lice also
develop resistance to the medicine used to kill them. Resistance
tends to be scattered. It may be present in one neighborhood,
but not another. However, there are many reasons why medications
may seem not to work.
- Misdiagnosis of a head lice infestation.
A diagnosis can be made if a person has crawling bugs on the
head or many lice eggs within 1/4 inch (about the width of
your little finger) of the scalp. Nits found on the hair
shaft further than 1/4 inch from the scalp have already
hatched. Treatment is not recommended for people who only
have nits further than 1/4 inch away from the scalp.
- Not following treatment instructions fully.
Common problems include:
- making the hair too wet with water before applying a
pediculicide — this dilutes the pediculicide
- using a creme rinse or conditioner shampoo before
applying a pediculicide — this interferes with the
- failure to leave the pediculicide on long enough —
follow drug label instructions
- re-shampooing the hair again immediately after
applying the pediculicide — don’t rewash hair for 1-2
days after treatment
- inadequate amount of medication — extra long hair
may require two bottles of pediculide to fully wet the
- not combing. Using medication alone may not be
enough to cure a head lice infestation. Combing the hair
to remove lice and eggs has been shown to help.
- Medication not working at all (resistance).
If head lice medication does not kill any crawling bugs
within 24 hours, then resistance is likely. If the
medication kills some of the bugs or the bugs are twitching
24 hours after treatment then resistance to medication is
probably not occurring.
- Medication kills crawling bugs, but is not able
to penetrate the eggs. It is very difficult for
head lice medication to penetrate the nit shell. Medication
may effectively kill crawling bugs, but may not treat the
nits. This is why follow-up treatment is recommended.
- New infection. You can get infested more than
once with head lice. Children often get re-infested
from a playmate. If your child is infested, discuss it with
parents of the children your child plays with. Treating all
infested children at the same time will help prevent
No. Head lice do not live on pets.
For children under 2 years old, remove crawling bugs and nits
using a nit comb. If this does not work, ask your child's health
care provider for treatment recommendations. The safety of head
lice medications has not been tested in children 2 years of age
Many head lice medications are available at your local drug
store. Each OTC product contains one of the following active
- Pyrethrins (pie-WREATH-rins) — often
combined with piperonyl butoxide (pie-PER-a-nil beu-TOX-side):
Brand name products include A-200*, Pronto*, R&C*, Rid*,
Pyrethrins are natural extracts from the
chrysanthemum flower. Though safe and effective, pyrethrins
only kill crawling lice, not unhatched nits. A second
treatment is recommended in 7-10 days to kill any newly
hatched lice. Treatment failures are common.
- Permethrin (per-meth-rin):
Brand name product: Nix*.
Permethrins are similar to
natural pyrethrins. Permethrins are safe and effective and
may continue to kill newly hatched lice for several days
after treatment. A second treatment may be necessary in 7-10
days to kill any newly hatched lice that may have hatched
after residual medication from the first treatment was no
longer active. Treatment failures are common.
- Malathion (Ovide*): When used as
directed, malathion is effective in treating lice. Some
medication remains on the hair and can kill newly hatched
lice for seven days after treatment. Malathion is intended
for use on people 6 years of age and older. Few side-effects
have been reported. Malathion may sting if applied to open
sores caused by scratching. The medication is flammable.
Click here for instructions on how to use malathion to treat
- Lindane (Kwell*): When used as
directed, the drug is probably safe. Overuse, misuse, or
accidentally swallowing Lindane can be toxic to the brain
and other parts of the nervous system. For those reasons
Lindane is generally used only if other medications have
failed. Lindane should not be used if excessive scratching
has caused open sores on the head. It should be used with
caution in persons who weigh less than 110 pounds.
If you aren’t sure, ask your pharmacist or health care
provider. When using the medicine, always follow the
instructions on the package insert unless the physician directs
When treating head lice
- Do not use extra amounts of the lice medication unless
instructed. These drugs are insecticides and can be
dangerous when misused or overused.
- Do not treat the infested person more than 3 times with
the same medication if it does not seem to work. See your
health care provider for alternative medication.
- Do not mix head lice drugs
No. Spraying the house is NOT recommended. Fumigants and room
sprays can be toxic if inhaled or absorbed through the skin.
Body lice (Pediculus
humanus) are closely related to head lice, but are less
frequently encountered in the US. As the name implies, body lice
generally feed on the body, but may rarely be discovered on the
scalp and facial hair. They usually remain on clothing near the
skin, and generally deposit their eggs on or near the seams of
garments. Body lice are acquired mainly through direct contact
with an infested person or their clothing and bedding, and are
most commonly found on individuals who infrequently change or
wash their clothes. A change to clean clothes, and laundering of
infested garments (especially drying with high heat or ironing),
are generally effective to eliminate this burden.
Pubic (Crab) Lice
Pubic or crab lice
(Pthirus pubis) have a short crab-like body easily
distinguished from that of head and body lice. Pubic lice are
most frequently found around the pubic region of the infested
person, but may also be found elsewhere on the body (including
facial hair and eyelashes). The infestation by pubic lice is
termed pthiriasis. Mechanical removal of these lice and
their eggs is the preferred method of treatment. Because pubic
lice are acquired mainly through sexual contact, their presence
may be associated with other sexually-transmitted diseases.
Pubic lice on a child may cause the physician to consider the
possibility that the child may have had inappropriate contact.
Pubic lice may also be acquired through more innocent means,
such as by sharing a bed with an infested person.
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Directory of Pest
This site is fascinating! We just
finished watching the new David Attenborough series on "Life in the
Undergrowth". These creatures you are identifying are very important to
life on the planet and I am very happy to have discovered your site
after watching the series! Spellbinding! thank you.... Beth
I'd like to add my sincere thanks to
everyone responsible for this very informative web site, especially Ed
Saugstad. Publishing 1000 pest photos and identifying them must
have taken many hours.
I recommend this site to all my students as a reliable learning
resource. Charles McD. Toronto.
Congratulations for having received
question #1000, and I'd also like to join the previous readers in
thanking Ed Saugstad for his conscientious work of providing great
answers to all questions; I also like this site a lot, I even added it
to my browser's toolbar! Best regards, -Peter (Canton, MI)
This is a wonderful web-site! I learn something
every time I visit, and have even had a couple of our own pests
identified by your resident experts (including the weevil, #989 which is
presently visiting our home, in northern Alberta) :)
What I really want is to send a big thank-you to Ed Saugstad
for the frequent responses and very helpful information, including
web-links, for the many "bugs" that appear on these pages. He clearly
loves what he is doing, and we are all beneficiaries of his beneficence.
Thank you, Ed!
Ted Drouin, retired biologist (not entomologist, though)
Thanks to Ted
Drouin and others for the kind words - this actually is fun, and teaches
me how little I really know!
I do some photography of various
critters found around my house (central Okanagan, BC) as well as
exotics from private collections. Often I have pictures I cannot
complete as I have no name. Your site helps me find these names.
Keep up the good work.
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