For years, many people out in the world have purchased and burned citronella candles in the hopes of keeping mosquitoes and other summer biting bugs away. A lot of us, actually, have questioned the efficacy of the products given that citronella has a distinctive smell and, frankly, doesn’t always work unless one is right on top of it.
Citronella geranium (citrosa) is claimed to repel mosquitoes within a 10 foot radius due to a continuous fragrant release of oil. However, research has repeatedly failed to back up these claims.
The Journal of the Mosquito Control Association published a study in 1996 that claimed no significant difference between citrosa-treated and nontreated subjects (1).
In another study in the same journal, the citrosa “mosquito plant” was assessed as a wide area repellent against adult, host seeking female mosquitoes (Aedes albopictus and Culex quinquefasciatus). Researchers noted no significant differences in the number of mosquitoes landing on the forearms of human subjects in locations where plants were present compared with areas without plants (2). In fact, the mosquitoes were observed to land and rest on the citrosa leaves directly.
So, the plant itself, by itself does not repel bugs. In fact, commercial citronella comes from completely different plant species. (Lemongrass, actually.)
Then why is the essential oil from citronella classified by the Environmental Protection Agency a bio-pesticide, meaning it repels bugs but is not toxic to the human body?
The National Pesticide Information Center describes oil of citronella as an effective repellent of insects. It works by masking scents that are attractive to insects, which in turn, makes it more difficult for insects to locate a target.
That would mean that to prevent a mosquito or other bug (say a chigger) from biting, the oil would have to be on the skin rather than in the air. It is NEVER a good idea to put essential oils directly on the skin. Always use a carrier oil, but as bug repellents go, this would be preferable. However, that is not a guarantee. Frankly, the research available on the subject does not agree. In Europe, citronella does not carry any such label.
Note: there are local, craft lotion producers that do formulate for bug repellent using citronella oil along with lemongrass, cedarwood, peppermint and more. This writer acquired a bar of such lotion and is anxious to try it out.