With the summer barbecue season underway in the Northern Hemisphere, many of us wonder if those citronella candles work even to keep stinging insects away.
Science tells us that mosquitoes are peculiar insects that cannot be generalized as much as we would like, which is why at the end of the barbecue some of the guests may be more bitten than others.
While we’re happy to sweep all the miserable bloodsuckers under the same ‘mosquito’ moniker, there are actually 112 genera containing 3,500 species that fall under that name. Similarly, insects’ methods of finding prey, as well as our deterrence and protection strategies, will naturally vary from species to species.
A mosquito fact sheet is imperative, therefore, to minimize the nuisance these insects can bring.
How do they find you
All mosquitoes use CO2 from human and animal breath as a guide to the location of a potential host. If you’ve ever seen them zigzagging through the air, that’s the sign that they just lost the smell of CO2 and are trying to find it again. Once you get them into the general position, they use visual features to look for signs of heat and olfactory odors to give them the exact position.
Human sweating increases the natural olfactory signals of lactic acid, ammonia, and other chemicals that mosquitoes use to find people, so people who sweat less are less likely to attract mosquitoes.
You can also find it through sweet-scented deodorant, body wash, shampoo, and other products, but they’ve been sucking our blood for millions of years, so you don’t need them.
Blood type is another often discussed factor in mosquito host detection. TO 1980 study When looking at blood type and malaria rates, it was found that people with blood type A, despite representing only 17.6% of the control group, constituted 29% of malaria cases, while that type O investigators, who were twice the number of types A, had only 22% of malaria cases.
Annoyingly, in stark contrast, a more modern study looked at blood type and secretions through the skin, and found that type O secretors were the most vulnerable. So the verdict on blood types is still murky.
We can’t change our blood type anyway, so let’s see what we can control.
Physical measurements are the main ones to use, long sleeves, high socks, etc., but it is also something that most people do not want to do in the height of summer.
Some modern outerwear has mosquito repellent infused into the yarn, which has been scientifically proven to work. However, the treatment fades over time and there are question marks in Canada about the safety of putting chemicals like permethrin next to the skin, especially for children. A common outdoor brand in England even recommends discarding treated clothing after a set number of washes.
DEET, a chemical called N, N-diethyl-meta-toluamide, It has been shown to be effective since 1957, and took its place as the common insect repellent ingredient for the US Army, before reaching civilian stores as well.
As the world’s most studied insect repellent, DEET has been shown to be remarkably safe. (Here is a 2020 study offer more scientific evidence.)
The authors of a 2002 study published in The New England Journal of Medicine wrote, “This repellent has undergone more scientific and toxicological scrutiny than any other repellent substance,” and they continue: “DEET has a remarkable safety profile after 40 years of use and almost 8 billion human applications ”, he concludes,“ When applied with common sense, DEET-based repellants it can be expected to provide a safe and long-lasting repellent effect. “
Most of the concerns can be attributed to people who use products with too high a concentration of the chemical or who use them improperly. Concerns about rare side effects of DEET, including skin irritation, shortness of breath, burning eyes, headaches, or
seizures, were reported after, in some cases, ingestion or application of the chemical in very large quantities.
Canada recommends not using a product that has a concentration greater than 30% and with a maximum limit of 10% for children under 12 years of age. As a precaution, manufacturers recommend that DEET products are not used on damaged skin and that preparations be washed off after they are no longer needed or between applications.
Still not convinced? Here are some alternatives.
Icaridin, also known as picaridin, is a good alternative to DEET and provides equivalent protection for up to 7 hours.
It is highly effective against various insects such as mosquitoes, ticks, gnats, flies, and fleas, and is nearly colorless and odorless. A study conducted in 2010 showed that a spray or cream at the 20% concentration it provided 12 hours of protection against ticks.
The compound was developed by the German chemical company Bayer and subsequently evaluated and recommended as a repellent by Consumer Reports. Commercial products that contain icaridin include Cutter Advanced, Skin So Soft Bug Guard Plus, and Autan.
Citronella, a formula commonly found in mosquito repellent candles, was actually listed as totally ineffective according to one study. The authors believe that it is actually accompanied vegetable oils, such as linalool and geraniol, that are sometimes added to the floral lemon-scented citronella that actually repel mosquitoes.
Of course studies looking at citronella candles containing linalool and geraniol found they were effective in deterring mosquitoes, about 85% and 71%, respectively.
Some products such as insect killers and others that reproduce high-frequency sounds that are supposed to interrupt mosquitoes. could be summarized in this excerpt from a study he investigated: “We are not aware of any scientific study showing that mosquitoes can be repelled by sound waves, and therefore we regard these devices as the modern equivalent of snake oil.”
Some soybean oil products are marketed as insect repellants, but Ada McVean writing for the McGill Office of Science and Society of Canada, Points out Soybean oil probably has nothing to do with the success of the products and is instead attributable to the other chemicals within these products, such as geranium oil, which is also used in citronella candles.
McVean sums up a good mosquito strategy by saying, “You should stay as odor-free as possible, wear light clothing, avoid swamps, and use an effective repellent (such as those containing DEET or icaridin).
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