A mosquito’s sole purpose in life is to suck blood from warm-blooded creatures and spread malaria, yellow fever, dengue, and other nasty diseases. But if repellents can keep us from getting bitten, why aren’t we all applying them liberally? For starters, some of us have the wrong idea about how repellents work against mosquitoes. Here’s what I often hear: “Repellents are useless because if you can’t smell them, they’re not working.” Wrong!
Prepare to be underwhelmed. An expert named Dr. James Logan used 3M Corporation’s human sensory research lab in St. Paul, MN, to find out which odors repel mosquitoes best—and it turns out that we humans are actually better at smelling than biting insects like mosquitoes and black flies. When a mosquito locks onto its target (after detecting carbon dioxide emanating from our skin), it first settles on the upper part of your body — especially the ankles — and starts taking small sips of blood.
The mosquitoes are so small (only about three-quarters of an inch long) that they can easily stand on your skin without noticing the repellent you’re wearing. Dr. Logan’s research showed that there is very little smell to the mosquito landing site, but as soon as it starts to probe for a blood vessel, some odor molecules from the repellent mix directly with its saliva and travel right back up its proboscis into its brain. It doesn’t take much to drive off these creatures; most effective odors at this stage have only two or three carbon atoms!
The top-performing olfactory distracters were DEET (N,N-diethylm-toluamide), picaridin (also known as Bayrepel® in the United States), and oil of lemon eucalyptus. Permethrin was acceptable, too, but it’s not safe to use on skin and can’t be applied to clothing.
In another study published in 2012 by a scientist at Rutgers University, DEET was much more effective than citronella candles or essential oils (even when used at triple the concentration recommended for maximum effectiveness). And while citronella candle manufacturers insist that their products are safe when used according to directions on the label — even for babies — don’t believe everything you hear!
Just because you have nothing bad happen after using a product doesn’t mean there aren’t any side effects. The next time you’re at an outdoor gathering, look around you and count the number of people who are sensitive to citronella — or any other insect repellent. You’ll probably see several people with bright red bumps on their necks or shoulders.
Because DEET has been used so widely since it was first developed in 1957, mosquitoes have become resistant to it in many places throughout the United States—and that’s why new products are being introduced every year. Each one is different from the last, and some react predictably only in certain parts of the country (where resistance hasn’t built up yet). While resistance isn’t a problem for picaridin or oil of lemon eucalyptus just yet, both tend to vaporize quickly into the thin air we breathe instead of attaching to your skin, which may be why they’re not as effective as DEET.
Most experts agree that the most important thing to know about mosquitoes is that they’re in the same class (arthropod ticks) as, spiders and scorpions. Unlike moths and other insects such as flies or beetles, mosquitoes don’t have mouths with mandibles (jaws) or even proper teeth; their primary mouthpart is a long, sharp-toothed straw called the proboscis. The shearing action between the two halves of this biting organ—along with its saliva’s digestive enzymes—makes it a lot like having little incisions all over your body!
Pinpointing exactly where you’ll encounter bloodsucking insects is no easy task, either. Some people attract more than others, and it’s not entirely clear why some people seem so much more appealing to mosquitoes than others. The truth may involve everything from body temperature to the particular metabolic byproducts you emit each day. But there are a few other tips that can help you avoid the next bite:
- Establish what time of day bugs like to bite most and try to spend as much time indoors during those hours as possible;
- Wear light-colored clothing (which reflects ultraviolet radiation from the sun and makes you look larger) and long sleeves if you know you’ll be outdoors for an extended period of time;
- Avoid wearing sweet-smelling perfumes or other fragrances, which might attract the insects;
- Don’t wear lotions or other products that will make you more attractive to mosquitoes by increasing skin temperature or otherwise altering your natural odor.
Some researchers have suggested wearing a thin veil of Off! Deep Woods ® Insect Repellent V11 ™ on clothing might help deter mosquitoes for up to 12 hours. If you’re like me, though, you probably hate the smell of DEET even more than being bitten! While citronella oil is definitely less offensive to most people than DEET, it’s no match for these creatures.
The best way to avoid bites this summer may well be simply donning a hat when outdoors — or in any area where biting insects are known to congregate—and tucking yourself into your favorite outdoor chair, away from the rest of the world.