Head Lice: Pediatrician's Perspective
Safety and efficacy are the key concerns
of the American Academy of Pediatrics
(AAP) when the organization establishes
treatment guidelines. During the development
of treatment guidelines for pediculosis,
which has no significant associated
morbidity and no mortality, the primary
concern of the AAP was the safety of products
used to treat infestations. Other information
included in the guidelines describes
social and economic consequences of lice
infestation. Specifically, although head lice
do not cause medical problems, infestations
do cause significant embarrassment and
social stigma, unnecessary days lost from
school because of no-nit policies, and direct
costs of treatment, as well as indirect costs
from lost productivity. In consideration of
these issues, the AAP published its clinical
report on the management of head lice in
2002 in an attempt to clarify issues of diagnosis
and treatment, and to make recommendations
for managing head lice in the
school setting.1
Diagnosis
The first challenge in effectively managing
head lice infestation is obtaining a correct
diagnosis. Observing live lice is the gold
standard of diagnosis, but lice are difficult to
see, and they can crawl 6 to 30 cm per
minute. Within a school setting, a nurse who
has only a minute per child to screen may
miss a louse that is well camouflaged or that
has crawled to another part of the child's
head during examination. Nits may be easier
to spot because they are stationary and
are generally laid within 1 cm of the scalp.
The nape of the neck and behind the ears
are good places to look for nits. Nevertheless, nits are small and difficult to see
with the naked eye, especially if lighting is
poor. It is important, also, to distinguish live
nits from empty egg casings or other materials.
Dandruff, hair casts, scabs, dirt, and
other insects are sometimes mistaken for
lice, even by physicians and nurses.1,2
General guidelines for assessing the viability
of a nit include its location and appearance.
Typically, a nit located farther from
the scalp than 1 cm is unlikely to be viable,
although lice in warmer climates may lay
eggs farther down the hair shaft.3 Also, a
viable nit develops a circular, eyelike marking
called an eyespot several days after being
laid. An eyespot can be seen with a 10×
hand-held magnifier or loop. Those responsible
for diagnosing infestations should keep
a few facts in mind about lice behavior and
transmission. Although lice can crawl relatively
quickly, they rarely travel far from a
preferred habitat, such as the warmth of the
scalp.2 They do not hop or fly. Lice cling
tightly to the hair, but they may attempt to
flee a heavily infested head and can be
found in the individual's collar, hats, or
other clothing worn near the head and
neck.1 They are transferred to others primarily
by head-to-head contact, although
fomites may sometimes carry lice. Lice
found in brushes and combs are usually
injured or damaged and are less likely to
infest another individual.4 Children should
be taught to not share combs, brushes, or
other items that touch the head, such as
scarves, hats, headphones, or helmets.
However, it is very important that children
always wear protective helmets when bicycling
or playing sports, even if the helmet
must be borrowed. The risk to a child from a
potential head injury far outweighs any risk
from head lice infestation. It is unlikely that
an infestation can be prevented, but transmission
can be minimized if adults know
warning signs of infestation and ensure that
children with lice are promptly treated.1
Treatments
OTC Preparations. Lice cause no medical
problem, so treatment must be as safe
as possible. From a pediatrician's point of
view, no amount of risk is acceptable. Treatment
options include pyrethroids such as
pyrethrin and permethrin 1%. These products
are available over-the-counter (OTC)
and are most likely to be used by parents of
children with lice. Available as shampoo or
crème rinse preparations, pyrethroids have
low mammalian toxicity and are generally
considered safe for most people. Pyrethroids
are not completely ovicidal, however, so a
second application is necessary within 7 to
10 days.1 Resistance to pyrethroid products
has been documented and is discussed
in greater detail in the article titled,
"Clinical Update on Resistance and Treatment
of Pediculosis capitis," found in this
supplement.
Prescription Products. Permethrin 5%, a
prescription product indicated for the treatment
of scabies, is also used by some
physicians to treat head lice. However, if
permethrin 5% is prescribed because of a
treatment failure of permethrin 1%, the child
might have permethrin-resistant head lice,
and the 5% preparation will be no more
effective than the 1% product.5
Lindane is an organochloride that has
recently garnered attention because of its
poor safety profile. The Food and Drug
Administration (FDA) has warned of potential
central nervous system toxicity and
increased risk for seizures and has recommended
that lindane be used with caution
only in a select population.6 In addition to
these safety concerns, widespread lindane
resistance has been documented.7
Malathion 0.5% is an organophosphate
that has been reintroduced in the United
States. Unlike other pediculicides, both OTC
and prescription, the prescription product
malathion 0.5% is approximately 98% ovicidal,
based on combined results of studies
conducted over the last 20 years. Also, no
resistance to malathion 0.5% has been
reported to date.1,7 (Other malathion products
marketed outside the United States have
lower ovicidal activity and are associated
with some resistance, depending on geographical
region.) Malathion is highly effective,
but the AAP guidelines note that this
product is a cholinesterase inhibitor, which
is associated with potential respiratory
depression if ingested. There are no reports
in the medical literature of respiratory
depression or poisoning associated with topical
malathion. Another concern about
malathion is its flammable alcohol base.1
Pediatricians worry about product labeling
instructions to leave malathion on the hair
for 8 to 12 hours, potentially prolonging risk
for the patient. However, no cases of burns
associated with malathion have been reported.
Researchers have found that malathion
may produce pediculicidal and ovicidal activity
within minutes, so it may be possible to
use this product effectively in less time,
decreasing patient risk.7 As with all products
that have a potential for toxicity in humans,
and because of its flammability, malathion
should be used only under a physician's close
supervision. The AAP guidelines suggest the
use of malathion with extreme caution and
only when OTC products such as pyrethroids
have been ineffective.1,8
Other prescription products including the
antibiotic cotrimoxazole and the anthelmintic
agent ivermectin are prescribed for
some cases of head lice infestation. These
products are not approved as pediculicides
by the FDA. Cotrimoxazole is associated
with risk for developing Stevens-Johnson
syndrome, and ivermectin should not be
administered to children who weigh less
than 15 kg.1
Preventing Pediculicide Resistance. Resistance
has been reported with all topical
pediculicides except malathion, significantly
limiting treatment options. Contributors to
increasing resistance include misdiagnosis
and improper use of pediculicides. If a child
is misdiagnosed as having lice, he or she will
be exposed unnecessarily to a pediculicide,
also potentially making the product less
effective if an infestation does occur.
Improper use of pediculicides includes
excessive dilution if too much water is left in
shampooed hair when the product is applied
and overuse or prophylactic use. Diluted
products are ineffective in killing lice and
allow the parasite to develop resistance over
time from repeated exposure to sublethal
doses. Similarly, excessive use overexposes
the product, making it less effective over
time. An important question for pediatricians
to ask when evaluating a seemingly
intractable infestation is whether the patient
may be reinfesting by failing to remove lice
or nits from the hair, clothing, or other items
that touch the head. If reinfestation occurs,
that doesn't mean that products that failed
in a first attempt will not work in the future.
Live lice should be removed, and nits should
be removed if the treatment is not ovicidal.
Pediculicide resistance should be confirmed
before using a prescription product.1
"Natural" Remedies. Parents who believe
that they can smother lice or otherwise
disrupt the respiratory system of the louse
often use occlusive agents. There is no scientific
evidence to support the efficacy of
occlusive agents. Similarly, manual removal
of lice, in the absence of other treatment, is
unlikely to be effective because lice may be
difficult to find or may crawl away during
the removal process.
School Control Measures
Routine screening for nits and lice is not
an effective means of reducing the incidence
of infestation.1 Given the total amount of
time required to perform screenings, it is not
the best use of the school nurse's time.
Other more important issues demand the
nurse's attention, and the time children miss
from class for screening is not justified by
results. Considering the short amount of
time most nurses have to screen each child,
often only 1 minute, the screening process
generally is not thorough enough to be accurate
and can provide a false sense of security.
Many school districts and some consumer
organizations, such as the National Pediculosis
Association, promote no-nit policies.
These policies generally call for dismissal of
a child from school until all head lice, nits,
and egg casings have been removed.9 Often
the child is sent home from school the day of
diagnosis. Research suggests that a child
with an active head lice infestation is likely
to have had the infestation for at least a
month by the time it is discovered and
therefore poses no immediate risk on the
day of diagnosis.1 Despite the assertion of
promoters of no-nit policies that a nit could
hatch and spread to a child the same day it
is discovered, hence the need to remove the
child from school immediately, there is no
medical evidence to support this position.
The AAP recommends using common sense
to assess each case. For example, a child
who has 2 live lice versus hundreds poses
less risk. The child should be discouraged
from close contact with other children, and
parents should be notified and asked to
promptly address the problem. In elementary
schools, an affected child's classmates
may be notified that an infestation has
occurred, but the child's confidentiality
should be protected.1
The AAP is working with school nurses to
discourage no-nit policies. Unfortunately,
school nurses often are pressured by school
administrators and parents to control infestations.
The no-nit policies may appeal to
laypersons, and it is difficult to explain why
they are not effective, particularly when
some consumer organizations strongly support
them. Nevertheless, there is no scientific
basis to confirm the effectiveness of such
programs, but there is research supporting
the view that the presence of nits poses only
a slight risk. In a 2001 study conducted in 2
metropolitan elementary schools, 1729 children
were screened for head lice. A total of
28 children (1.6%) had lice, and 63 (3.6%)
had nits with no lice. After 14 days, 18% of
children with nits alone developed lice.
Researchers concluded that having 5 or
more nits within 1/4 inch of the scalp
increased the risk of conversion, but most
children with nits and no lice did not
become infested. The study also concluded
that exclusionary policies for children with
nits alone are excessive.10
Conclusion
Safe treatment of children with head lice
infestation is the primary objective of the
AAP. Unfortunately, overuse and inappropriate
use of pediculicides may expose children
to unnecessary risk and contribute to resistance.
Several pediculicides are available to
treat head lice infestation, but resistance has
been documented for all products except
malathion. Prescription products should be
used conservatively and only under close
supervision by a physician.
School measures that are designed to
control infestations may in fact be detrimental.
Specifically, no-nit policies result in lost
time from school, inappropriate allocation of
the school nurse's time for screening, which
is often ineffective, and a response to infestations
that is out of proportion to their
medical significance. The AAP guidelines for
control of head lice infestation include recommendations
for accurate diagnosis, safe
treatment options, and a common-sense
approach to managing infestations in a
school environment.