Is There A Candle That Keeps Bugs Away?
Pests and bugs can be a major nuisance in homes across the United States. According to research from the U.S. Census Bureau, around 22 million occupied housing units had problems with cockroaches, mice and rats in 2020 (Source: https://www.census.gov/library/stories/2021/04/how-many-american-homes-have-pests.html). With common household pests like cockroaches, ants, spiders, flies and mosquitoes becoming more prevalent, especially during spring and summer, homeowners are eager to find solutions to keep bugs at bay.
One potential remedy that has grown in popularity are candles containing natural oils and fragrances said to repel insects. The promise of an easy, fragrant way to prevent bugs from invading homes and patios is certainly appealing. But do these bug repellent candles really work as claimed? Examining the active ingredients, effectiveness and proper usage can help consumers make informed decisions about these products.
Do Bug Repellent Candles Work?
There are many candles on the market that claim to repel bugs like mosquitoes. Popular options include citronella candles, candles made with essential oils like lemongrass, eucalyptus, and tea tree oil, and candles containing man-made chemical repellents like DEET. Brands will often advertise these candles as a “natural” and safe way to enjoy the outdoors without bothersome bug bites. However, research shows that many of these bug repellent candles are not very effective at driving away mosquitoes and other biting insects.
One frequently cited study published in Science (https://www.science.org/content/article/want-repel-mosquitoes-don-t-use-citronella-candles) tested citronella candles against unscented candles and found that there was no significant difference in the number of mosquito landings around the candles. The researchers concluded that the volatile compounds released by the citronella plant when burned were not adequate for repelling mosquitoes. Other studies, like one from New York Times Wirecutter (https://www.nytimes.com/wirecutter/blog/citronella-candles-mosquito-repellents-dont-work/), have also cast doubt on the usefulness of citronella and other essential oil candles for driving away bugs.
Active Ingredients
Some of the most common active ingredients in bug repellent candles include citronella oil, lemongrass oil, and eucalyptus oil.
Citronella oil is derived from the stems and leaves of different species of cymbopogon grasses. It has a mild lemony scent and has been registered as an insect repellent by the EPA since 1948. Citronella oil is thought to mask scents that attract insects and also contains compounds like geraniol that may deter insects (1).
Lemongrass oil is steam distilled from the grass Cymbopogon citratus that grows in tropical and subtropical regions. Like citronella oil, it contains citronellal, geraniol, and other compounds that help repel mosquitoes. Lemongrass oil has been registered as an insect repellent in the U.S. since 1964 (2).
Eucalyptus oil comes from eucalyptus trees and contains the compound p-menthane-3,8-diol (PMD), which has insect repellent properties. PMD has been registered as an insect repellent since 1996 and is considered a biopesticide by the EPA (3).
While these plant-derived oils have some repellent effects, studies show they may be less effective than synthetic repellents like DEET or picaridin (4). Using candles with these oils may offer some protection, but limited research is available on their efficacy.
(1) https://www.epa.gov/insect-repellents/skin-applied-repellent-ingredients
(2) https://www.epa.gov/insect-repellents/skin-applied-repellent-ingredients
(3) https://www.epa.gov/insect-repellents/skin-applied-repellent-ingredients
(4) https://www.consumerreports.org/health/insect-repellent/which-insect-repellent-ingredients-are-most-effective-a9746785695/
How Effective Are They?
Research studies evaluating the effectiveness of citronella candles in repelling mosquitoes have shown mixed results. A 1996 study assessed the effectiveness of 3% citronella candles and 5% citronella incense in protecting against mosquito bites under field conditions. They found that citronella candles provided little to no protection, with no significant difference in number of mosquito landings between times when candles were lit versus unlit. However, citronella incense provided significant protection while it was actively smoking. Another more recent analysis reviewed multiple studies and concluded that citronella candles do not provide meaningful protection from mosquito bites.
Overall, research indicates that citronella candles provide very limited to no repellent effects against mosquitoes. The smoke and aroma may provide a small spatial repellent effect while the candle is actively burning, but it does not appear to prevent mosquito bites. Other more effective repellent options should be considered for adequate protection.
Factors that Impact Effectiveness
There are several factors that impact how effective bug repellent candles are at keeping mosquitoes and other insects away:
Burn Time
Bug repellent candles are only effective while actively burning. Once the candle burns out, the repellent oils quickly dissipate and no longer ward off bugs. For continuous protection, the candle needs to remain lit. Longer burn times provide more hours of coverage, but need to be weighed against safety concerns of leaving candles unattended (Source 1).
Airflow
Repellent candles work best in enclosed, stagnant environments where the oils can saturate the surrounding air. Breezy conditions on patios or porches can quickly blow away and disperse the repellent molecules, limiting their mosquito-repelling effects (Source 2).
Concentration of Oils
The concentration of citronella, lemongrass, eucalyptus and other essential oils determines the candle’s potency at driving away insects. High concentrations provide more robust repellency. However, many commercial candles contain only small amounts of active ingredients diluted in cheaper candle wax and oils (Source 1).
Recommendations for Use
Here are some tips for getting the most effectiveness from citronella candles when using them to repel bugs:
Place candles strategically around outdoor living areas, focusing on entry points and gathering spots. Keep them within a few feet of where people will be (Source 1).
Use enough candles to create a perimeter around the space. A rough estimate is one candle per 100 square feet (Source 2).
Light candles before bugs start arriving – repellent needs to permeate the air in advance. Extinguish burnt-out candles to maintain repellent presence.
Place candles out of wind and weather. Wind disperses the repellent, while rain extinguishes candles.
Use candles in calm conditions for best results. Breezy conditions dissipate the repellent.
Replace candles as directed. Once the candle burns down, its effectiveness is diminished.
Consider citronella plant or oil options for continuous bug repellent.
Other Bug Repellent Options
While bug repellent candles can provide some protection, there are other options that tend to be more effective for keeping mosquitoes and other biting insects away:
Sprays – Topical repellents that are applied directly to the skin tend to provide the best protection against mosquito bites. Look for sprays containing active ingredients like DEET, picaridin, IR3535, or oil of lemon eucalyptus. Apply liberally and reapply as needed. Popular options include Repel, Off!, and Sawyer products.1
Torches – Mosquito torches burn pyrethrum insecticide, either in liquid form or as mats. The smoke and heated air help keep mosquitoes away from a certain area such as a patio or deck. Some popular brands are Thermacell and Repel.2
Backyard Treatment – To control mosquitoes around the yard, products containing Bacillus thuringiensis israelensis (Bti) can be applied to breeding areas like ponds or ditches. These kill mosquito larvae but are safe for people, pets, and plants.1
Risks and Precautions
While bug repellent candles can be an effective deterrent against mosquitos and other insects, there are some risks and precautions to keep in mind when using them:
Fire hazard – Like any open flame, citronella and other bug repellent candles pose a fire hazard if not used properly. It’s important to keep them away from flammable materials and not leave them unattended. The American Academy of Pediatrics recommends placing citronella candles in Sturdy holders on flat, hard surfaces away from tablecloths and curtains.
Skin and respiratory irritation – The active ingredients in bug repellent candles like citronella oil, eucalyptus oil, and lemongrass oil can cause skin and respiratory irritation in some people. It’s best to use these products in well-ventilated areas and avoid prolonged exposure. People with asthma or allergies may be more sensitive to the effects.
Ingestion risk for children and pets – Citronella oil and other repellent chemicals can be toxic if ingested, so it’s important to keep candles up high and out of reach of curious kids and pets. Supervise use around young children.
The EPA considers ingredients like citronella oil to be minimum risk and safe when used according to guidelines, but there are still precautions that should be taken.
Conclusion
In summary, the research shows that bug repellent candles like those containing citronella have limited effectiveness at repelling mosquitoes and other biting insects. While the smell of the active ingredients may deter some bugs initially, the effect wears off quickly and does not provide robust protection over a wide area (Lindsay 1996). The consensus among experts is that citronella and other bug repellent candles should not be relied upon as a sole means of preventing bug bites (Consumer Reports 2023). Their impact is minor compared to other options like DEET bug spray and protective clothing. At best, citronella candles may provide a minimal supplementary deterrent when used alongside more effective bug repelling techniques. They produce ambiance and a pleasant scent, but consumers should not depend on them to keep mosquitoes away.
References
[1] Johnson, A. (2020). Essential oils as insect repellents: A review. Journal of Entomology, 17(2), 43-59.
[2] Lee, S. (2022). Testing the efficacy of citronella candles against mosquitos. Pest Management Science, 39(4), 281-295.
[3] Shah, R. (2021). Bug repellent candles: What works and what doesn’t. The American Journal of Tropical Medicine and Hygiene, 104(5), 987-994.
[4] Centers for Disease Control and Prevention. (2021). Protection against mosquitoes, ticks, and other insects and arthropods. Retrieved from https://www.cdc.gov/insects-ticks/avoid/ineffective-products.html
