A popular bug repellent, citronella candles are made of wax, citronella and other essential oils. The candles are wide, stout and often produce some smoke, which aids in repelling insects. The width of the candle also provides a larger wax pool, which allows the heated oils to disperse into the air. Citronella candles are comprised of wax, a wick and essential oils in a flame-proof container, such as a clay pot or small metal bucket.
Citronella oil is obtained from the leaves and roots of plants in the Cymbopogon species, including the Ceylon and Java varieties, which have different concentrations of citronellal and geraniol, the key insect-repelling ingredients. Both are effective at repelling insects and are considered organic, according to the U.S. Environmental Protection Agency.
Clove oil is obtained from the flower bud of the clove plant, which is an evergreen tree. According to PioneerThinking.com, clove oil is a skin irritant, so it should be used sparingly and with caution. However, it also an effective repellent mixed into a citronella candle.
Obtained from the leaves of peppermint plants, peppermint oil improves the fragrance of the candle as well as enhances the effectiveness. According to AnniesRemedy.com, peppermint oil has a long history as a pest repellent. The website states that rat catchers in the early 1900s used peppermint-soaked rags to deter rats and that ants are repelled by the scent.