Many mosquito repellents contain synthetic chemicals such as DEET. If you prefer to use natural skincare products, citronella oil, oil of lemon eucalyptus (p-Menthane-3,8-diol) and IR3535 are natural mosquito repellents with proven effectiveness.
Citronella oil has been used as an insect repellent for over 50 years and is the active ingredient in insect repellent candles, incense sticks, smoke coils and some topical skin repellent sprays, lotions and wipes. Oil of citronella repels mosquitoes, ticks, black flies and fleas, but it does not harm insects - it works by disguising the chemicals given off by humans that mosquitoes find attractive.
Oil of citronella is classed as a biopesticide because it is derived from natural plant-based substances. It is not expected to cause harm to humans, animals or the environment. (Biopesticides are less toxic to the environment than conventional pesticides and degrade quickly.) Citronella oil is obtained from the steam distillation of freshly cut or dried grasses Cymbopogon nardus and Cymbopogon winterianus. Commercially-prepared "Ceylon" citronella oil comes from Cymbopogon nardus, and "Java" citronella is from Cymbopogon winterianus.
Research suggests citronella insect repellents vary in their effectiveness and may not be as reliable as other repellents. Fradin and Day, 2002, found the protection times of citronella-based insect repellents were not as long as insect repellents containing DEET, IR3535 and soybean oil. No citronella insect repellents tested could provide protection for more than 20 minutes.
In a laboratory evaluation of synthetic and natural mosquito repellents against three species of mosquito, Barnard and Xue, 2004, found mosquito repellent spray containing 10 percent citronella performed better overall than four other natural mosquito repellent formulations. Its protective effects were not, however, as long lasting as picaridin, soybean, IR3535, oil of eucalyptus, or DEET-based insect repellents. Average protection times for the citronella insect repellent varied greatly between mosquito species.
According to the U.S. Environmental Protection Agency (EPA), oil of citronella has been used widely since 1948 without giving cause for concern. When used according to instructions, citronella is unlikely to be harmful to humans, domestic pets, wild animals or the environment. Skin irritation may be a concern for some people, but serious adverse effects are extremely unlikely. Citronella insect repellents may need more frequent application than other insect repellents.
Citronella candles are scented with citronella oil and come in all shapes and sizes. Choose from citronella votive candles, glass, bucket, torch, pillar and tea light candles, as well as smoke coils and incense sticks.
According to the American Mosquito Control Association, citronella candles are only effective when there is no wind blowing and are less effective than topical insect repellents applied to your body or clothing. A study carried out by the University of Guelph, Canada, found people standing near 3 percent citronella candles and 5 percent citronella incense received significantly fewer mosquito bites than people standing near unscented candles or in candle-free areas.
It appears citronella candles do not offer you complete protection against insect bites, but they will help reduce the number of bites you receive if you stay close to them, within the vicinity of the smoke. If you are having a summer barbeque, fill your garden with outdoor candles, coils and incense sticks so all your guests can get some protection against the mozzies. Your garden will also have the added benefit of a warm, inviting glow, a pleasant atmosphere and a nice smell.
Oil of Lemon Eucalyptus (p-Menthane-3,8-diol)
Oil of lemon eucalyptus is an essential oil steam-distilled from the leaves of lemon-scented eucalyptus trees (Eucalyptus citriodora). In scientific tests, the active ingredient in oil of lemon eucalyptus, p-menthane 3,8-diol (also known as PMD, Citriodiol or Citrepel), has been shown to be highly effective for repelling insects. Thus, p-menthane 3,8-diol is registered for use as an insect repellent by the U.S. Environmental Protection Agency (EPA) and endorsed by the U.S. Centers for Disease Control and Prevention (CDC), having satisfied the necessary requirements for efficacy and safety.
In the context of insect repellents, it is important to make the distinction between p-menthane 3,8-diol and oil of lemon eucalyptus. p-menthane 3,8-diol is synthesized from leaves of the Australian lemon-scented gum tree and is an EPA-registered insect repellent. Pure oil of lemon eucalyptus essential oil has not received the same testing as p-menthane 3,8-diol and therefore is not registered for use as an insect repellent by the EPA.
Peer-reviewed scientific studies have shown p-menthane 3,8-diol provides long-lasting protection against mosquito bites. According to the CDC, PMD insect repellent offers similar protection against mosquitoes to low-level DEET insect repellents. Furthermore, insect repellents based on oil of lemon eucalyptus provide longer-lasting protection than other plant-derived insect repellents.
In a study published in the Journal of the American Mosquito Control Association, Carroll and Loye (2006) discuss the performance of p-menthane 3,8-diol as an insect repellent against several species of mosquito. Based on their review of numerous research studies involving insect repellents, they conclude that not only is the CDC correct in recommending PMD as an insect repellent, but that the CDC may have underestimated the importance of PMD as an effective alternative to DEET-based repellents.
In an informative article entitled “Bug Off! Which Mosquito Repellents Work Best?”, published in Slate online magazine (2005), writer Andria Lisle describes how she and her friends offered themselves as a mosquito buffet during the Memphis summertime, in order to test the performance of a range of chemical and natural insect repellents.
The testers rated Off! Botanicals Lotion, which contains the active ingredient p-menthane 3,8-diol, as the best performing insect repellent. Repel Lemon Eucalyptus Spray, also containing PMD, was the runner up. Repellents containing the active ingredients DEET and citronella also performed well, while soybean oil, IR3535, picaridin and permethrin trailed behind.
p-menthane 3,8-diol is classified as a biopesticide and is found in a range of natural insect repellents, including Mosiguard, Incognito, Off! Botanicals, Lifesystems Natural Insect Repellent and Ben’s Natural Insect Repellent. According to the CDC, oil of lemon eucalyptus products should not be used on children aged less than 3 years.
IR3535, also called Merck 3535, is also a biopesticide derived from natural ingredients and is registered for use as a mosquito repellent by the U.S. Environmental Protection Agency. Mosquito repellents typically contain between 7.5 and 20.07 percent IR3535. Some Avon mosquito repellents contain IR3535.
When choosing a natural mosquito repellent, be sure to check the active ingredients to help determine how effective it will be. Also remember that just because a mosquito repellent is labelled as "natural", it does not necessarily mean it is safe. Any mosquito repellent can potentially cause a skin reaction.
Barnard D. and R.D. Xue. 2004. Laboratory evaluation of mosquito repellents against Aedes albopictus, Culex nigripalpus, and Ochlerotatus triseriatus (Diptera: Culicidae). Journal of Medical Entomology 41:726-730.
Carroll S.P. and J. Loye 2006. PMD, a registered botanical mosquito repellent with deet-like efficacy. Journal of the American Mosquito Control Association 22:507-514.
CDC: "FAQ: Insect Repellent Use and Safety".
CDC: "Updated Information Regarding Insect Repellents".
EPA: "Citronella (Oil of Citronella) (021901) Fact Sheet".
EPA: "p-Menthane-3,8-diol (011550) Fact Sheet".
EPA: "R.E.D. Facts: Oil of Citronella".
EPA: "What Are Biopesticides?"
Fradin MS, Day JF. Comparative efficacy of insect repellents against mosquito bites. N Engl J Med. 2002; 347(1):13-8.
Slate: "Bug Off! Which Mosquito Repellents Work Best?"