Healthy Facts: Head Lice (Pediculosis)
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Life Cycle
The head louse is one of three types of lice that infest people.
These tiny insects (about 1/10 to 1/8 of an inch long) make
their home in human hair and feed on human blood. Head lice
multiply rapidly, laying small greyish-colored oval-shaped
eggs (called nits) which they glue to the base of the hair,
close to the scalp.
Signs of Head Lice Infestation
Although head lice are hard to find, you can see the nits
if you look closely. They are most often found along the hairline
at the back of the head and neck and behind the ears. Nits
should not be confused with an accumulation of hair spray,
hair gels or dandruff. Dandruff can be easily flicked off
the hair; nits cannot because they are firmly attached to
individual hairs.
Who Can Get Head Lice?
Anyone can get head lice. They are not a sign of being dirty.
Most people don't know they are infested until they see the
nits or lice. One telltale sign of head lice is a persistent
itching of the scalp which is sometimes accompanied by infected
scratch marks or what appears to be a rash.
How Does an Infestation Occur?
Head lice have no wings and do not fly or jump, but they can
run through hair quickly. You can "catch" head lice through:
- Direct contact with an infested person;
- Sharing personal items such as combs, brushes, other hair-care items, towels and pillowcases;
- Sharing clothing, headgear (hats, scarves, football and batting helmets, etc.), ribbons and other head coverings.
Shared school lockers and unassigned wall hooks for coats have been associated with higher rates of infestation than individual lockers.
Treatment and Control
If you have questions concerning diagnosis and treatment of
head lice, call your doctor or public health department. The
recommended treatment includes using either a prescription
or over-the-counter (OTC) medicated (lice-killing) product.
Effective head lice treatments include (1) "Nix,” a cream
rinse product available OTC which contains permethrin, a synthetic
insecticide; (2) many brands of pyrethrin-based shampoo products
("RID", "R&C", "Triple-X", etc.) which are also available
OTC; and (3) "Ovide", a prescription drug containing malathion.
With all of these products, the lice are usually killed with
one treatment; however a second treatment 7 to 10 days later
is often necessary to ensure all of the nits are killed. Because
there have been reports of treatment failure with the OTC
products, when re-treating make sure instructions on the product
are being carefully followed or talk to your health care provider.
Shampoos containing lindane ("Kwell,” etc.) are no longer
the first choice for head lice treatment because of the risk
of neurological toxicity associated with lindane.
Dead nits do not fall off the hair after treatment. Because they are strongly cemented on, they.are often difficult to remove. A nit comb or fingernails can be used to remove nits. Nits remaining in the hair after treatment should not be confused with live nits. Head lice lay their eggs very close to the scalp, and they hatch within a week -- before the hair grows more than 1/4 inch. Nits found any farther along on the hair shaft than ½ inch will have already hatched or been killed during treatment and their removal is not necessary.
Alternative Treatments
Many alternatives to OTC or prescription head lice control
products have been suggested. Although there is little scientific
information to support these methods, successful treatment
has been reported using several alternative treatments when
conventional treatments haven't worked, or when there is a
concern about the toxicity of using head lice control products
repeatedly. The Minnesota Department of Health cannot recommend
these treatments without further evidence of their effectiveness.
However, we feel it is important to mention some of the more
commonly used methods.
The alternative treatments listed below are referred to as suffocants. When applied, the treatment may suffocate and/or create a habitat unfavorable to the head lice.
- Petroleum jelly (Vaseline®)
- Mayonnaise
- Oil (e.g., vegetable, olive, or mineral)
Clean Up
Head lice cannot survive off the human body for more than
two days. They do not reproduce off the body. They do not
live on pets. Any nits that fall off the head will not hatch
or reattach. To keep head lice from returning, you should
do the following:
- Wash bedding in hot water (above 130 degrees F) and dry in a hot dryer or iron with a hot iron. Wash and dry recently worn clothing (including coats, caps and scarves) in hot temperatures. Clothing or bedding that cannot be washed may be dry cleaned or sealed in a double plastic bag for two weeks.
- Clean combs, brushes and similar items by:
- soaking in the medicated shampoo for 10 minutes, or
- soaking in a 2% Lysol solution for one hour, or
- heating in water of at least 130 degrees F for 10 minutes.
- Clean floors, carpeting and furniture by thorough vacuuming only. The use of insecticide sprays is not recommended.
Prevention
When it is known that head lice are present in a community,
parents are encouraged to check their children's heads for
lice on a regular basis throughout the year. Families should
not depend on someone else to check a child’s head–this may
delay treatment. Remember, if one person in a family,
camp or school has head lice, there's a chance others will
too. Check everyone, and use the same treatment if necessary.
The Minnesota Department of Health makes the following recommendations to schools concerning head lice:
- School districts should make their own policies on whether or not to do "head checks" at school. Parents should not rely on school staff to check for lice but should do this at home, whether or not the children are checked at school.
- Infested children do not need to be dismissed from school.
- When a case of head lice is found, notices should be sent home to inform parents and advise them to check for lice in their children's hair.
Note: The use of brand names is for identification purposes only, not for product endorsement.
Minnesota Department of Health, Acute Disease Investigation
and Control Section.
May be reproduced, unchanged, without permission. 2002
