Head Lice
Pediculosis capitis refers to symptoms caused by human head lice infesting the head hair of a
person. Head lice are not known to transmit infectious agents, nor do they discriminate among socioeconomic
groups. They are more commonly found on children of preschool and early elementary
school age. Overall, about 1% of 5-12 year olds are infested. Girls are infested more often than boys,
and parents and siblings sometimes acquire head lice. Lice and their eggs (called nits) are usually
limited to the head hair. |
|
Life Stages of Head Lice
Nit (louse egg) - Nits are laid onto the hair shaft, close to the scalp. They
are oval in shape and may undergo several color changes as they develop.
They take 8-12 days to develop and hatch. With magnification the developing
nymph may be seen within the egg. Eggs that have died or hatched will
remain firmly attached to the hair, but will never again produce another louse.
Nymph - The nymph is the immature stage of the louse. These look just
like an adult louse, only smaller and are unable to reproduce yet. They mature
into adults in about 9-12 days after hatching. Nymphs must feed on human
blood to survive and grow.
Adult - Adults are about the size of a sesame seed, have six legs, are
wingless, and may be tan to grayish-white or even have a reddish tinge. Adult
females may live up to 30 days on the head of the infested person. As with
nymphs, they feed once or more often each day. Lice are unable to survive
longer than 1-2 days away from the human body and are unable to live on
pets.
Signs, Symptoms, and Transmission
Students with head lice are usually asymptomatic, but some may experience
itching from an allergic reaction to the bites or irritation from sores
caused by bites. Transmission occurs from head to head contact with an
infested person. The transmission from hats, combs, pillows, etc. is possible
but much less likely.
Reasons for chronic infestations
- Resistance to treatment (Lice on children who are treated repeatedly are more likely to be
resistant to treatment.)
- Ineffectiveness of treatment
Diagnosis
Head lice may be found anywhere on the head hair, but are often easiest to locate on the scalp
behind the ears and near the neckline at the back of the neck. Adult female lice deposit nits on the hair
about 1 mm from the scalp. Under good lighting and using a comb, search the head for viable nits and
crawling lice. Live lice are sometimes difficult to see as they move quickly and there are usually less
than 10 lice on a head. Tape the live louse on a white background and view with magnification to see
it more clearly.
Treatment
Treatment is recommended only for individuals found with live lice or viable eggs. If nits are found
further than about ¼ inch from the head, they are probably hatched and no longer viable.
- Nit Combs. Combing with a nit comb can sometimes be effective in removing viable nits and
lice. Nits that are more than ¼ inch from the scalp are not likely to be viable and need not be
removed. Comb daily until no live lice are discovered for two weeks. Recheck in 2-3 weeks after
you think all lice are gone.
- Over the counter lice shampoo. As with all drugs, directions must be followed exactly. These
products may be rinsed from the hair over a sink rather than shower or bath to limit exposure to
the body. A second treatment may be required in about 10 days.
- Prescription lice shampoo medications. These products contain other insecticides that require
greater care for treatments, and should be used only under a physician’s care, and only if live lice
persist following treatment with the over-the-counter products. Parents should be advised to
discuss with their health care provider specific instructions for use of these products, potential
risks and benefits, and other possible treatment recommendations.
- Alternative treatments (petroleum jelly, mayonnaise, margarine, herbal oils, enzyme-based
products and olive oil) should be avoided as there is no conclusive evidence that these
treatments are effective or necessarily safe. Oils may facilitate the absorption of insecticides in
shampoos.
Family members of a student with head lice should be encouraged to inspect themselves to see if
lice are present. All individuals found with lice should be treated simultaneously. Inform family
members that bedding, towels, nightclothes, and other clothing that was in contact with the head within a
day of treatment should be washed and/or dried in the dryer at high heat (if appropriate). Combs, brushes,
and hair accessories used by the student should be rinsed in hot water each day until lice are eliminated.
Do not treat the premises with pesticides! Treating rooms, carpets, desks, etc. is not recommended.
Vacuuming floors, especially carpets recently occupied by infested persons are recommended. Lice
will soon die (generally within two days) once off the head for a day. Nits attached to hair that have
fallen from an infected person will likely stop developing and will also die within a few days. Although
it is not necessary to thoroughly clean school busses, vacuuming floors of classrooms or homes
occupied by infected persons will help dispel concerns about lice or eggs that may have dropped from
an infected person. Clothing, pillows, cloth toys, and other items that may have been used by infested
children may be treated by heating in a clothes dryer on high heat or by sealing in a plastic bag for two
weeks.
Recommendations for School Policy
- Routine head check of healthy students is not recommended.
- Check symptomatic students.
- When nits ¼ inch or closer to the scalp or live lice are discovered, do not exclude from school, but
notify the parent that day and provide instructions on how to treat and eliminate.
- The school nurse may offer extra help to families with chronic infestations.
The American Academy of Pediatrics recommends that no healthy child be excluded from or
allowed to miss school because of head lice, and discourages ‘no nit’ policies for return to school.
The National Association of School Nurses state that nit-free policies disrupt the education
process and should not be viewed as an essential strategy in the management of head lice.
Health and Health Care in Schools. Children with nits do not pose an immediate threat to the
health of others; therefore, excluding these children from school and requiring them to be treated with a
pesticidal product is probably excessive.
Printable Version [PDF]
Additional Resources:
IPM Plan for Head Lice (Texas A&M)
Head Lice Fact Sheet [PDF] (Maine Center for Disease Control and Prevention)
Management and Control of Head Lice (University of Florida School IPM)
Photo credits:
Dani Barchana, Self employed, Bugwood.org
|
