There are very few things more annoying than buzzing flies when you’re trying to enjoy time outside. They land on your skin or your food or travel down into your beverage. Swatting at them doesn’t work half the time and when it does, two more flies show up to replace the one you got rid of. But, you’ve heard about citronella candles for mosquitoes and you may be wondering: Do citronella candles work for flies?
Unfortunately, the answer isn’t so easy. Citronella candles can work to repel flies, but they’re not the most effective means of doing so. The fact is that citronella oil itself is a known insect repellent, but the amount that’s typically added to candles isn’t enough to do the job. And even if it was, other factors can make the candles less than effective.
So read on to learn the truth about flies and citronella candles. You may be surprised at what you discover.
How Citronella Oil Keeps Bugs Away
Since the mid 20th century, citronella has been used as an insect repellent. Many people assume that, since citronella has a unique and strong smell, it works to actively repel flies and other insects. In reality, citronella works by masking the scents that insects use to locate humans and other mammals. In short, citronella is only effective if there’s enough of it to confuse the insects’ senses and send them looking for another target.
For this reason, applying diluted citronella oil directly to the skin has been shown to work for 30 minutes to an hour before it needs to be replenished. When applied to the skin, the oil is able to mask the smells that insects use to locate humans. But, since citronella oil is volatile, it evaporates quickly, which is why it only lasts a short time.
When you realize that this is how citronella works to keep flies away, it’s easy to see why citronella candles aren’t the best option.
How Effective is a Citronella Candle in Keeping Flies Away?
Most of the studies concerning citronella candles have been done on mosquitoes and biting or sand flies. One study showed that sand flies were reduced by 15.4% within 1-meter of the candle. Outside of that 3.3-foot radius, the efficacy dropped quickly.
Even for mosquitoes, for which citronella candles are often marketed as a repellent, the numbers aren’t great. Studies show an average maximum effectiveness of 50% within three feet of the burning candle.
So, while the studies are lacking for citronella candles and modern house flies, we can reasonably assume how effective these types of candles are. At best, citronella candles will keep about half of the flies away. This makes them one of the least effective methods for repelling flies on the market.
Why Aren’t Citronella Candles Good Fly Repellents?
For a citronella candle to be effective at keeping flies away, certain conditions must be met. Unfortunately, many of these conditions are out of our control, including the amount of oil in a given candle, wind conditions, and the specific type of fly we’re trying to repel. One thing we can control is how close we are to the candle as it burns. Let’s take a brief look at these conditions.
Percentage of Citronella Oil in a Candle
High concentrations of citronella oil can cause irritation to children, the elderly, and pets. Serious effects are rare, but this may be one reason why companies don’t put very much oil in their citronella candles. Unfortunately, this is also a reason why these types of candles aren’t very effective. The average concentration of citronella oil in a repellent candle is 5%. Some brands use even less.
As a result, there simply isn’t enough of the masking oil to do its job.
Even in those rare candles where citronella is used in higher concentrations, wind becomes an issue. In order for the citronella oil to mask a human’s smell, it has to hang around in the air. When it’s windy— even just a slight breeze— the citronella oil scent is taken away from the area, making it even less effective.
In the same instance, you should never use a citronella candle indoors or in any place that isn’t ventilated well. It’s a kind of catch-22. Works best when there’s no wind, but should only be used outside.
Type of Fly
As mentioned above, most of the studies of citronella candles have been done on mosquitoes. Some species of biting flies have been affected by citronella candles, but the percentages aren’t much better than those of mosquitoes. Some kinds of flies may be better equipped to locate humans even through the haze of citronella oil a candle provides.
Distance from Candle
The one condition we can control is the distance from the candle. They’re found to be most effective within about 3 ½ feet. Unfortunately, this limits what you can do outside. If you’re having a party or a BBQ, you’ll have to purchase a dozen or more citronella candles to keep the flies and other insects away. Either that or give every person a candle to carry around with them. What a sight that would be!
In this way, citronella candles aren’t the most cost-effective method. Plus, there’s the smoke and other chemicals being released into the air. Many party-goers may not want to breathe in the smoke from these candles all day or night. Which brings us to the safety aspect.
Are Citronella Candles Safe?
Citronella candles are considered safe when the directions for use are followed. This usually means that they are lit and used outdoors in a well-ventilated area. High concentrations of citronella oil have been shown to have adverse effects for the very young and the elderly, but this is not a normal occurrence. Of course, breathing any sort of smoke is not the best thing in the world for you, whether from a regular candle or one made to repel flies.
If you’re set on using citronella candles, make sure you read the warnings first. Sometimes these candles are made with suspected carcinogens and other chemicals that are best to avoid if possible. However, this varies depending on the candle manufacturer.
None of the above should be considered medical advice. Always talk to a qualified medical professional for health questions concerning citronella candles and insect repellents.
There’s not a lot of concrete scientific evidence pertaining to house flies and citronella candles. But, when you look at how citronella oil works as a repellent, and the studies done on other types of flies, the results aren’t promising.
At best, burning a citronella candle can keep some flies away. And this is only if you’re within three feet of the candle, there is little or no wind, the candle has enough citronella oil in it, and the type of flies around or susceptible to the masking effects of the oil.
With so many other fly repellent options on the market, like disposable fly traps, there’s little reason to use citronella candles. Unless, of course, you like the smell of the ambiance they create.