To Whom It May Concern:
In response to your inquiry, I would like to inform you of our opinions
regarding school health policies relating to head lice.
For more than five years, the Field Epidemiology Research Team (F.E.R.T.)
at the University of Miami School of Medicine has conducted research on head
lice infestations. This team has personally treated over two thousand cases
of pediculosis, examined more than 15,000 nits or eggs, and we have
extensively studied the biology of the human head louse. We have,
therefore, gained considerable experience and are generally considered the
experts with the most hands on knowledge of the subject.
Much of the data on the biology of lice stems from work conducted in the
cool climate of England in the 1940's and earlier. Our findings in more
temperate climates (75°F to 85°F) differ in several respects from these
These warmer conditions represent ambient outdoor conditions in the
summer months over most of the U.S. and indoor temperatures in schools and
houses throughout the year.
1) Our most important finding is that viable eggs (nits) shed from the
scalp on hairs remain viable until hatched. We can transport collected eggs
thousands of miles, and obtain over 90% hatching a week to ten days later.
Within 30 seconds of hatching, the new born nymphs can move quickly to the
nearest person and start to take the first blood meal.
Viable eggs shed into the environment, or on combs, brushes,
head gear, etc., remain capable of hatching up to 10 or 12 days.
Lice normally take a blood
meal every three to four hours, but they can survive up to 8 hours between
feedings, and can do so off the body. They can travel up to 12 inches per
minute, and are attracted to warmth and body odor. Thus lice hiding in
scarves, head gear, etc., placed on coat hooks or in lockers will quickly
move to the next warm item placed nearby, throughout the school day.
Head lice ban be transferred by inanimate objects and
Although most eggs are laid near the scalp, in warmer
climates (75°F to 85°F or higher), we frequently find viable eggs several
inches from the scalp. If the temperature and humidity are suitable, female
lice will lay their eggs anywhere. This finding is particularly true in
long haired female children.
Distance from the scalp is not an indicator of viability.
Parents, teachers and school nurses usually lack the
experience to distinguish a viable from a non-viable egg. Teachers and
health care personnel are reluctant to lay hands on infested children in
order to conduct the careful examination required to rule out infestation.
A new born nymph is almost transparent, and no larger than the period at the
end of this sentence. The responsibility of finding lice and removing nits,
therefore, rests with parents and older siblings.
We support the National Pediculosis Association's 'No Nit
Policy’. It is an important factor in limiting epidemics, and is the only
practical method of ensuring that children are free of viable eggs.
Professor of Dermatology,
Epidemiology and Public Health