Citronella Oil Citronella Oil is one of the oldest and better known natural insect repellents on the market. People have planted citronella plants in their garden for years as a way to scare off mosquitoes, ticks, and other insects, too. Results from several University studies demonstrate that citronella oil can help provide toxic-free mosquito protection. Lemongrass Oil With its proven track record for repelling mosquitoes, lizards and bees, lemongrass is a safe and heavenly smelling partner. Rosemary Oil Another plant based oil that has shown to have mosquito repellent effects and it's best used in combination with any of the other oils listed above.