Pure essential oil and a topical formulation from lemongrass oil (Cymbopogon citratus) Stapf. have been investigated for repellent activity against Acarus sacchari and mosquitoes respectively. To two sugar cubes were applied two drops of the oil each. The first cube ‘depleted treated sample’ was used after 48 h of application while the second cube (freshly treated sample) was used immediately after application. Varying doses of the topical formulation on the other hand were applied to the exposed forearm and leg of each volunteer in a mosquito-infested location. The time of the first three mosquito bites or lands were recorded. The depleted and freshly treated sugar samples exhibited 81% and 95% repellency respectively against Acarus sacchari while the topical formulation from lemongrass oil exhibited an average of [(194) min (≈3 h) for 0.5 g dose] and [(309) min (≈5 h) for 1.5 g dose] protection time against biting from mosquitoes, (about 50-80%) protection time in comparison to the activity of the best known chemical insect repellent, N, N-diethyl-m-toluamide (DEET). It can be concluded that lemongrass oil is a promising natural repellent due to its safety advantage over chemical repellents.
