The yellow fever mosquito, Aedes aegypti, poses public health issues to human populations around the world. Aedes aegypti is a vector of multiple debilitating diseases, including dengue fever, yellow fever, zika, and chikungunya. Numerous synthetic insecticides have been developed to control Aedes aegypti populations. The effectiveness of these chemicals in mosquito control has been diminished due to the prevalence of insecticide-resistant mosquito populations. Insecticide resistance may be acquired via mutations in genes encoding target receptors and enzymes, or from upregulation of detoxifying enzymes. Plant essential oil toxicity has been well established in laboratory conditions, and plant essential oils are known to be capable of enhancing insecticides. This study assessed the ability of plant essential oils, when applied topically, to modulate detoxification enzyme processes in Aedes aegypti. Three enzyme systems were examined: cytochromes p450, glutathione S-transferase, and esterase. Select plant essential oils were identified as capable of inhibiting cytochromes p450 de-ethylase activity, and many caused a decrease in glutathione S-transferase activity. Additionally, one plant essential oil decreased esterase activity. This study highlights some physiological interactions that contribute to the effectiveness of plant essential oils as insecticide additives.