Lemongrass is a tall plant native to the tropics. The stalks contain the same type of oil that is found in lemon peel and has a similar scent. This oil is commonly known as the basic ingredient found in citronella candles, according to the Epicentre Encyclopedia of Spices.
Drugs.com reports that lemongrass was tested in experiments involving adult mosquitoes using different levels of the oil in paraffin. While other tests have been done on lemongrass, Drugs.com adds that clinical data on its usefulness as an insect repellent are still incomplete.
Organic Impact suggests growing your own lemongrass and making an extract from it that you can spray on your skin. An easy way to extract the oil from the plants is to cut the lemongrass into small pieces and soak it in water for a few hours, using 2 cups water for every cup of lemongrass.