Timothy J. Gibb,
Insect Diagnostician, Department of Entomology, Purdue University
The following picture of the
week shows the development of head lice on the shafts of human
hair. Many questions arise every
year concerning head lice and children. Typically, the presence
of head lice elicits a frenzy of spraying, cleaning, laundering
and other activities by parent teachers and school staff. I am
much more concerned about the negative health effects of indiscriminate
pesticide spraying in busses, homes or classrooms than I am about
head lice. The fact that head lice cannot survive off a host
for more than a few hours, casts huge doubts about the effectiveness
of bus sprays. I would not recommend them at all.
There is a lot of talk about
insecticide resistance in head lice, however, there is much less
documented evidence. I personally
think it is over rated. Head lice are difficult to control
and easy to spread, thus reinfestation is usually what accounts
for people’s perception of resistance.
pyrethrin, malathion and Lindane are all chemicals that can be
used. Chances of any insect becoming resistant to all of
these products at once is just about zero. Rotating pesticides
is the best way to ensure that resistance does not occur.
Using mechanical measures (combs
and thorough inspections) in conjunction with chemical treatments
is really the best solution. Washing
personal items (combs, hats etc) also may help to some degree.
Other products (like Debug) are
based on little scientific information. The
thought is that the enzymes render the hair much more difficult
for a louse to lay its eggs on or for the nits to stick to the
hair shafts (dissolves the glue material nit needs to stick).
Again, the scientific testing in most
of these products is not complete enough to say whether they will
or will not work.