Do Citronella Candles Really Work Outside?
Citronella candles are a common product marketed as a way to repel mosquitoes and other insects when spending time outdoors. The candles contain oil from citronella grass, a plant whose fragrance is believed to act as a natural insect repellent. Manufacturers claim that the aroma from citronella candles creates a protective bubble that keeps bugs away from a certain area, making these candles a popular item during mosquito season for backyard gatherings, camping, and other outdoor activities. However, while citronella candles are widely used for this purpose, there has been debate around whether they are truly effective at deterring mosquitoes and other pests. This article explores the evidence behind citronella candles and whether the aroma they emit reliably keeps insects away or if consumers should look to other options for bug protection when spending time outside.
How Citronella Candles Are Supposed to Work
Citronella candles contain citronella oil, which is an essential oil extracted from lemongrass plants (Want to repel mosquitoes? Don’t use citronella candles). The strong scent of citronella oil is supposed to help repel mosquitoes and other insects when it is diffused into the air by the candle’s flame.
The theory is that mosquitoes are deterred by the smell and will avoid areas where citronella candles are in use. Some people believe that citronella oil masks other attractive scents like carbon dioxide from breathing that draw mosquitoes to humans and animals (Citronella Candles Don’t Really Work. Stop Buying Them.).
Therefore, burning a citronella candle is thought to create a protective bubble of sorts around the candle where mosquitoes and other biting insects will be less likely to enter.
Studies on the Effectiveness of Citronella Candles
Several scientific studies have analyzed whether burning citronella candles effectively repels mosquitoes in outdoor spaces. In one major study published in the Journal of the American Mosquito Control Association in 1996, researchers tested 3% citronella candles and 5% citronella incense under field conditions (https://pubmed.ncbi.nlm.nih.gov/8827606/). They found that the candles provided an average of 42.3% protection from mosquito bites for 1 hour, while the incense provided an average of 24.2% protection. However, the protection declined sharply after 1 hour, with almost no effect after 2 hours.
Another study published in Malaria Journal in 2001 tested 5% citronella candles in Thailand and found they provided only 42 minutes of complete protection time against mosquito bites on average (https://malariajournal.biomedcentral.com/articles/10.1186/1475-2875-20-123). The researchers concluded the candles should not be relied upon for full protection.
A controlled study from 2021 found virtually no repellent effect from citronella candles against Aedes mosquitoes, the species that spreads diseases like yellow fever, dengue, Zika, and chikungunya (https://www.science.org/content/article/want-repel-mosquitoes-don-t-use-citronella-candles). The researchers recommended avoiding citronella candles for mosquito control.
Overall, most scientific research indicates citronella candles provide only partial and temporary protection against mosquitoes when used outdoors. The repellent effect appears minimal beyond 1-2 hours of use.
Factors That Impact Effectiveness
There are several factors that can influence the effectiveness of citronella candles in repelling mosquitoes:
Wind is one major factor. Citronella candles release a scented plume of smoke that is supposed to repel mosquitoes. However, wind can disperse the scented smoke and dilute its concentration, making it less effective at repelling mosquitoes from a given area 1.
Distance from the candle is also important. Research indicates the repellent effects of citronella candles are only moderately effective within a 3 feet radius around the candle. The effectiveness diminishes further from the candle, providing little to no protection at distances greater than 10 feet 2.
Burn time and candle size can impact effectiveness. Small citronella tealights may only protect a small area for an hour or two. Larger candles or torches designed to burn all night may be more effective for protecting a slightly bigger area over a longer period 3.
Proper placement is also key. For the best results, citronella candles should be placed near seating areas or high-traffic zones where mosquito protection is most needed. Placing them upwind helps their scent spread better as well.
Recommendations for Usage
To get the most mosquito protection from citronella candles, there are some usage tips to keep in mind:
Place candles near seating or dining areas where you’ll be stationary for a period of time. Mosquitoes are less likely to come near the candles when people are sitting close by versus candles placed in unused spaces. According to experts at Lumabase, citronella candles work best when burned within 3-6 feet of where people are located.
Use multiple citronella candles to increase the repellent coverage area. Spacing candles every 10-15 feet around patios or decks can provide a “mosquito-free bubble.” The more citronella scent in the air, the less appeal for mosquitoes according to Citronella Graziani.
Place candles downwind from where you’ll be to allow the scent to drift towards you. Position candles based on the direction of the prevailing breeze.
Extinguish other competing scents from foods, perfumes, or additional candles that can mask the citronella smell.
Use citronella candles along with other precautions like applying bug spray. Layering repellent methods provides extra protection according to experts at NY Times.
Other Precautions
In addition to using citronella candles, there are some other precautions you can take to avoid mosquito bites:
Wear insect repellent on exposed skin. Look for repellents that contain DEET, picaridin, IR3535, or oil of lemon eucalyptus. Follow the instructions on the product label and reapply as directed. According to the CDC, repellents containing 20% or more DEET provide longer-lasting protection. [1]
Avoid being outdoors during peak mosquito hours. Mosquitoes that transmit diseases are most active during dusk and dawn. Limit outdoor activities during these times when possible.
Wear loose, long-sleeved shirts and long pants. Covering up skin can provide a barrier against bites.
Make sure window and door screens are in good repair. Screens prevent mosquitoes from entering your home.
Eliminate sources of standing water around your home. Mosquitoes lay eggs in stagnant water. Get rid of items that collect water like old tires, empty pots, etc. Clean gutters and change water in bird baths frequently.
[1] https://www.cdc.gov/mosquitoes/mosquito-bites/prevent-mosquito-bites.html
Natural Alternatives
There are some natural options that may help repel mosquitoes without relying on chemical insecticides. Certain plants contain natural oils that can deter mosquitoes, such as citronella, lavender, basil, catnip, marigolds, and geraniums. Strategically planting these around outdoor living spaces creates a barrier that makes it harder for mosquitoes to reach you (Source).
You can also use essential oils like lemon eucalyptus, citronella, peppermint, lemongrass, and rosemary to make homemade bug sprays. Dilute the oils in water and put in a spray bottle. Be sure to reapply often as the oil will evaporate quickly. Some people also use oil diffusers with these essential oils to create a mosquito-repelling aroma in outdoor areas (Source).
In terms of plants, some top options to consider are:
- Citronella grass – gives off a strong scent that confuses mosquitoes
- Marigolds – contain pyrethrum that is toxic to mosquitoes
- Catnip – has nepetalactone oil that repels mosquitoes
- Lavender – has fragrance mosquitoes dislike
- Rosemary – has antioxidant compounds mosquitoes avoid
- Basil – contains compounds like linalool that deter mosquitoes
While not as strong as DEET, using plants and natural oils throughout your outdoor areas can provide some extra protection from mosquitoes. They add pleasant natural scents while avoiding synthetic chemicals.
Synthetic Insect Repellents
Synthetic insect repellents like DEET (N,N-diethyl-meta-toluamide) are considered the most effective mosquito repellents available. Multiple studies have found DEET to provide longer protection compared to plant-based repellents like citronella oil.
For example, a 2015 study published in the Journal of the American Mosquito Control Association tested multiple mosquito repellents, including DEET and citronella oil, on humans (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4617422/). The researchers found that 20% DEET provided complete protection from mosquito bites for over 4 hours, while 2% soybean oil (which contains citronella) only provided complete protection for about 1 hour. DEET also showed higher effectiveness in protecting against both host-seeking and blood-feeding mosquitoes compared to citronella oil.
Another article from NPR reviewed evidence on mosquito repellents and concluded that DEET-based repellents provided the best protection, while citronella candles were found ineffective in studies (https://www.npr.org/sections/goatsandsoda/2018/06/30/623865454/a-guide-to-mosquito-repellents-from-deet-to-gin-and-tonic).
Overall, the research clearly shows that synthetic repellents like DEET are more effective than plant-based options like citronella for protecting against mosquito bites. Citronella candles do not provide the same level of mosquito protection compared to topical synthetic repellents.
Other Mosquito Control Methods
In addition to citronella candles, there are several other techniques used for mosquito control:
Mosquito traps like the Mosquito Magnet Patriot Plus Mosquito Trap [1] use heat, carbon dioxide, and other attractants to lure mosquitoes into a trap. Traps can capture thousands of mosquitoes, but may not eliminate all mosquitoes from an area.
Backyard spraying with insecticides like Cutter Backyard Bug Control Concentrate Spray [2] can provide temporary relief by killing adult mosquitoes, but doesn’t have lasting effects. Frequent reapplication is needed.
Larvicides like Summit Mosquito Bits [1] kill mosquito larvae in standing water before they can mature into biting adults. This targets mosquitoes at the source but requires identifying and treating all breeding grounds.
Government mosquito control programs may spray large areas or release genetically modified mosquitoes to suppress populations. Community-wide efforts provide broader control than individual backyard measures.
Conclusion
In summary, while citronella candles contain oils that act as mosquito repellents, studies have found them to only be marginally or moderately effective at repelling mosquitoes in outdoor settings. Their effectiveness depends on several factors, including proper usage, wind conditions, and having an adequate number of candles for the space. Compared to other options, citronella candles are less effective than synthetic repellents applied directly to the skin, but provide a nicer ambient experience than something like DEET. They also require more effort in placement and replacement compared to set-it-and-forget-it mosquito control systems like propane trap machines. However, citronella candles are a more natural and inexpensive option that may work well enough for some outdoor situations where 100% mosquito protection isn’t critical. They can provide some measure of repellency, especially when used in combination with other precautions. Overall, citronella candles should not be relied upon as a sole mosquito deterrent, but can be a helpful addition to an integrated pest management plan.
