Protection against arthropod bites is best achieved
by avoiding infested habitats, wearing protective clothing,
and applying insect repellent.
11,12
The insect repellents
that are currently available to consumers are
either synthetic chemicals or are derived from plants.
The most widely marketed chemical-based insect repellent
is DEET, which has been used worldwide since
1957. DEET is a broad-spectrum repellent that is effective
against many species of mosquitoes, biting flies,
chiggers, fleas, and ticks.
17
The protection provided
by DEET is proportional to the logarithm of the dose;
higher concentrations of DEET provide longer-lasting
protection, but the duration of action tends to plateau
at a concentration of about 50 percent.
18
Most commercially
available formulations now contain 40 percent
DEET or less, and the higher concentrations are
most appropriate to use under circumstances in which
the biting pressures are intense, the risk of arthropodtransmitted
disease is great, or environmental conditions promote the rapid loss of repellent from the
surface of the skin.
19
In our study, a formulation containing
23.8 percent DEET provided an average of
five hours of complete protection against
A. aegypti
bites after a single application. Depending on the formulation
and concentration tested, DEET-based repellents
have been shown in other studies to provide
complete protection against arthropod bites for as
long as 12 hours, even under harsh climatic conditions.
20,21