By Glynn Wilson –
Do mosquitoes seem to bug the crap out of you, but even more annoyingly, seem not to bother some of your friends and family?
I’ve long wondered why the pesky critters love me so much. If women loved me as much as mosquitoes, I would have a harram.
Since it is August on the Gulf Coast — and I’m really tired of getting bit every time I walk out the door — I finally got around to looking it up on the web.
Here’s some of what I found. Who knew my taste for good beer could have something to do with it?
The bugs didn’t seem to bother my momma in Birmingham in recent years. Then again she had diabetes. Nothing pops up in the research about that, but people with diabetes don’t seem to be bothered by mosquito bites.
About the first thing that pops up in a Google search is this article from WebMD, a publication I used to write for some.
Could it be that mosquitoes prefer to bite some people over others?
The short answer is yes.
Mosquitoes do exhibit blood-sucking preferences, say the experts.
“One in 10 people are highly attractive to mosquitoes,” reports Jerry Butler, PhD, professor emeritus at the University of Florida.
But it’s not dinner they’re sucking out of you. Female mosquitoes — males do not bite people — need human blood to develop fertile eggs. And apparently, not just anyone’s will do.
Who Mosquitoes Like Best
Although researchers have yet to pinpoint what mosquitoes consider an ideal hunk of human flesh, the hunt is on.
“There’s a tremendous amount of research being conducted on what compounds and odors people exude that might be attractive to mosquitoes,” says Joe Conlon, PhD, technical advisor to the American Mosquito Control Association. With 400 different compounds to examine, it’s an extremely laborious process.
“Researchers are just beginning to scratch the surface,” he says.
Scientists do know that genetics account for a whopping 85 percent of our susceptibility to mosquito bites. They’ve also identified certain elements of our body chemistry that, when found in excess on the skin’s surface, make mosquitoes swarm closer.
“People with high concentrations of steroids or cholesterol on their skin surface attract mosquitoes,” Butler says.
That doesn’t necessarily mean that mosquitoes prey on people with higher overall levels of cholesterol, Butler explains. These people simply may be more efficient at processing cholesterol, the byproducts of which remain on the skin’s surface.
Mosquitoes also target people who produce excess amounts of certain acids, such as uric acid, explains entomologist John Edman, PhD, spokesman for the Entomological Society of America. These substances can trigger mosquitoes’ sense of smell, luring them to land on unsuspecting victims.
But the process of attraction begins long before the landing. Mosquitoes can smell their dinner from an impressive distance of up to 50 meters, explains Edman. This doesn’t bode well for people who emit large quantities of carbon dioxide.
“Any type of carbon dioxide is attractive, even over a long distance,” Conlon says. Larger people tend to give off more carbon dioxide, which is why mosquitoes typically prefer munching on adults to small children. Pregnant women are also at increased risk, as they produce a greater-than-normal amount of exhaled carbon dioxide. Movement and heat also attract mosquitoes.
Mosquitoes sense movement and head toward you. When you pant from exertion, the smell of carbon dioxide from your heavy breathing draws them closer. So does the lactic acid from your sweat glands.
With a long track record — mosquitoes have been around for 170 million years — and more than 175 known species in the U.S., these shrewd summertime pests clearly aren’t going to disappear any time soon.
In another piece by from Smithsonian Magazine, we learn that an estimated 20 percent of people are especially delicious for mosquitoes, and get bit more often on a consistent basis.
And while scientists don’t yet have a cure for the ailment, other than preventing bites with insect repellent (which, we’ve recently discovered, some mosquitoes can become immune to over time), they do have a number of ideas regarding why some of us are more prone to bites than others. Here are some of the factors that could play a role.
Not surprisingly—since, after all, mosquitoes bite us to harvest proteins from our blood—research shows that they find certain blood types more appetizing than others. One study found that in a controlled setting, mosquitoes landed on people with Type O blood nearly twice as often as those with Type A. People with Type B blood fell somewhere in the middle of this itchy spectrum.
Additionally, based on other genes, about 85 percent of people secrete a chemical signal through their skin that indicates which blood type they have, while 15 percent do not, and mosquitoes are also more attracted to secretors than nonsecretors regardless of which type they are.
One of the key ways mosquitoes locate their targets is by smelling the carbon dioxide emitted in their breath—they use an organ called a maxillary palp to do this, and can detect carbon dioxide from as far as 164 feet away. As a result, people who simply exhale more of the gas over time—generally, larger people—have been shown to attract more mosquitoes than others. This is one of the reasons why children get bit less often than adults, on the whole.
Exercise and Metabolism
In addition to carbon dioxide, mosquitoes find victims at closer range by smelling the lactic acid, uric acid, ammonia and other substances expelled via their sweat, and are also attracted to people with higher body temperatures. Because strenuous exercise increases the buildup of lactic acid and heat in your body, it likely makes you stand out to the insects. Meanwhile, genetic factors influence the amount of uric acid and other substances naturally emitted by each person, making some people more easily found by mosquitos than others.
Other research has suggested that the particular types and volume of bacteria that naturally live on human skin affect our attractiveness to mosquitoes. In a 2011 study, scientists found that having large amounts of a few types of bacteria made skin more appealing to mosquitoes. Surprisingly, though, having lots of bacteria but spread among a greater diversity of different species of bacteria seemed to make skin less attractive. This also might be why mosquitoes are especially prone to biting our ankles and feet — they naturally have more robust bacteria colonies.
Just a single 12-ounce bottle of beer can make you more attractive to the insects, one study found. But even though researchers had suspected this was because drinking increases the amount of ethanol excreted in sweat, or because it increases body temperature, neither of these factors were found to correlate with mosquito landings, making their affinity for drinkers something of a mystery.
Scientists don’t say whether mosquitoes like any old beer like Bud — or a brewpub IPA.
In several different studies, pregnant women have been found to attract roughly twice as many mosquito bites as others, likely a result of the fact the unfortunate confluence of two factors: They exhale about 21 percent more carbon dioxide and are on average about 1.26 degrees Fahrenheit warmer than others.
This one might seem absurd, but mosquitoes use vision (along with scent) to locate humans, so wearing colors that stand out (black, dark blue or red) may make you easier to find, at least according to James Day, a medical entomologist at the University of Florida, in commentary he gave to NBC.
As a whole, underlying genetic factors are estimated to account for 85 percent of the variability between people in their attractiveness to mosquitoes—regardless of whether it’s expressed through blood type, metabolism, or other factors. Unfortunately, we don’t (yet) have a way of modifying these genes, but…
Some researchers have started looking at the reasons why a minority of people seem to rarely attract mosquitoes in the hopes of creating the next generation of insect repellants. Using chromatography to isolate the particular chemicals these people emit, scientists at the UK’s Rothamsted Research lab have found that these natural repellers tend to excrete a handful of substances that mosquitoes don’t seem to find appealing. Eventually, incorporating these molecules into advanced bug spray could make it possible for even a Type O, exercising, pregnant woman in a black shirt to ward off mosquitoes for good.
Let’s hope they find the answers soon.
Zika, West Nile, Malaria, Dengue Fever are all spread by the pesky bugs, making people sick all over the world. Zika is now beginning to show up in South Florida and other places in the U.S.
© 2016, Glynn Wilson. All rights reserved.