Simultaneous exposure to
DEET and
permethrin was recently proposed to be associated with the "
Gulf War Syndrome." However, no studies have reported the percutaneous absorption of
DEET and
permethrin when applied simultaneously to the skin as a mixture, the relevant route of exposure in the Persian Gulf. The present study quantitates percutaneous absorption of
DEET and
permethrin after coadministration to rodent and pig skin in vitro. Dosing solutions were also prepared with either
acetone,
dimethyl sulfoxide (
DMSO), or
ethanol to compare vehicle effects on percutaneous absorption of
permethrin and
DEET. The influence of
DEET on
carbaryl absorption and dermal disposition was also assessed in pig studies to statistically demonstrate
DEET effects in
acetone or
DMSO and different
solvent concentrations. Topical application of
permethrin +
DEET resulted in absorption of
DEET (1-20% dose), but no
permethrin.
Permethrin (1.2-1.7% dose) was detected only when mouse skin was dosed solely with
permethrin, a finding suggesting that
DEET decreased
permethrin absorption.
DEET also inhibited
carbaryl absorption in
acetone mixtures, but had no effect on
DMSO mixtures. Irrespective of
solvent,
DEET did not enhance
carbaryl penetration into skin. For
DEET, absorption was greater in mouse skin (10.7-20.6% dose) than in rat skin (1.1-5.2% dose) and pig skin (2.8% dose). The extent of
DEET absorption was greater with
DMSO and
acetone than with
ethanol in rat and mouse skin. These studies support
DEET, but not
permethrin or
carbaryl, as having sufficient systemic exposure to potentially cause signs of toxicity when simultaneously applied with pesticides. Furthermore, these studies demonstrated that
DEET does not necessarily enhance dermal absorption of all toxicants as was originally hypothesized.