The mechanism
responsible for insect repellency in citronella is the masking
of CO2 or lactic acid discharged by humans that attracts
mosquitoes and other insects. Citronella is found on the list
of chemicals that may not require EPA registration in some
cases. Unless a product containing citronella is EPA
registered, it has not been subject to EPA review and the
EPA cannot corroborate its safety and effectiveness. Oil of
citronella goods are often marketed as repellent candles,
although topical preparations offer insect defense as well
(EPA, 2009).
Oil of lemon eucalyptus (active ingredient: PMD) was
discovered to provide insect defense comparable to low
concentrations of DEET (EPA, 2009; CDC, 2010).