Your body chemistry is irresistible
First, a little entomology fact: Only female mosquitoes bite, when they’re looking for the protein (from blood) necessary to lay eggs. The rest of the time, mosquitoes feed off of sugar from plants, says Paul Breslin, PhD, a professor of nutritional sciences at Rutgers University and a researcher at the Monell Chemical Senses Center in Philadelphia. “So, while they love sugar, that doesn’t mean mosquitoes are attracted to people who have ‘sweet’ blood. Rather, they let their senses guide them; and, some people are smellier than others,” says Breslin. “It’s similar to if you were to walk into a kitchen after someone bakes an apple pie—you’d be drawn to the smell.” Your aroma comes from a variety of places, like your breath (this isn’t halitosis, or bad breath, though—different aspects of metabolism, such as blood-sugar levels, can affect the scent profile of your exhale) and/or the bacteria on your skin, which differs for everyone. Even your genes may affect your odor.
Unfortunately, your own unique smell stamp isn’t something you can really change. Trying to mask your odor with perfumes or body lotions doesn’t generally help—floral scents tend to draw the pesky bugs in even more—but these is one surprising exception: this Victoria’s Secret fragrance. Dousing yourself in it may repel mosquitoes effectively for up to two hours, according to a 2016 study in the Journal of Insect Science.
You’re sipping a beer
Sure, it’s refreshing on a hot summer evening, but cracking open a cold one could also be a mosquito lure. One small study found that after people drank beer, the number of mosquitoes that landed on them increased. compared to a control group. Another study in PLOS ONE that looked at the species of mosquito known to carry the malaria virus found that beer-drinking participants became more attractive to the pests than those downing H20. One hypothesis was that beer increases the amount of carbon dioxide exhaled—but that’s not what researchers found happened. Instead, they discovered that brewskis altered a person’s body odor, causing mosquitoes to veer toward them like a bull’s-eye.
You’re in a big group
Here you are, having fun at an outdoor party, when the ‘uninvited guests’ drop by. From long distances, mosquitoes track you by the CO2 plume you exhale, says Jorge Rey, PhD, director and professor at the Florida Medical Entomology Laboratory. Although everyone exhales about the same amount of CO2 individually, the total amount is exponentially higher the larger the group you’re with. Translation: The crowd attracts them. From longer distances, mosquitoes are also attracted to movement and dark colors (which they can see better). When they close in, they then find you via your body chemistry. Your best defense—besides being antisocial or putting on lighter-colored clothing—is wearing repellent. DEET, picaridin, IR3535, oil of lemon eucalyptus and 2-undecanone are five effective ingredients to look for on labels, says the EPA. Long-sleeved shirts and pants will also help protect against bites.
If you’re expecting, you’re likely already actively trying to avoid mosquitoes because of Zika (the virus that can be passed to the fetus and can cause birth defects like microcephaly). Being proactive—wearing mosquito repellents, avoiding traveling to areas known for the virus—is crucial because mosquitoes seem to be even more drawn to pregnant women. An older study from 2000 found that pregnant women attracted about two times the number of mosquitoes as women who weren’t pregnant did. It could be from an increase in body heat, but also “it’s likely due to changes in hormones, which alter their body odor in some way,” says Rey.