For as long as I can remember, I have been that friend—the one who, from May to November, gets invited to every outdoor soiree. It’s not because I make the best desserts, even though I do. It’s because, with me around, the shoes can come off and the DEET can stay sheathed: No one else need fear for their blood when the mosquitoes are all busy biting me.
Explanations abound for why people like me just can’t stop getting nipped—blood type, diet, the particular funk of the acids that emanate from our skin. Mosquitoes are nothing if not expert sniffers, evolving over millennia to detect the body’s many emissions, including the carbon dioxide we exhale and the heat we radiate.
But to focus only on a mosquito’s hankering for flesh is to leave a whole chapter of the pests’ scent-seeking saga “largely overlooked,” Clément Vinauger, a chemical ecologist at Virginia Tech, told me. Mosquitoes are omnivores, tuned to sniff out blood and plants. And nowadays, most humans, especially those in the Western world, tend to smell a bit like both, thanks to all the floral, citrusy lotions and potions that so many of us slather atop our musky flesh.
That medley of scents, Vinauger and his colleagues have discovered, may be an underappreciated part of what makes people like me smell so darn good to pests. The findings are from a small study with just five volunteers, four brands of soap, and one mosquito species, and still need to be confirmed outside the lab. But they’re a reminder that, as good or as bad as some of us might inherently smell to a mosquito, the insects experience us as dietarily diverse smorgasbords—not just as our animal selves.
Researchers have also long known that “everything we use on our skin will affect mosquitoes’ behavior or attraction toward us,” says Ali Afify, a mosquito researcher at Drexel University. That includes extracts from plants—among them, chemicals such as citronella and limonene, which have both been found to repel the bloodsucking insects in at least some contexts. Something about encountering floral and faunal cues together seems to bamboozle mosquitoes, as if they’re “seeing an organism that doesn’t exist,” says Baldwyn Torto, a chemical ecologist and mosquito expert at the International Centre of Insect Physiology and Ecology. After all, female mosquitoes, the only ones that bite, spend their lives toggling between seeking nectar and hunting for blood, but never both at the same time. That’s part of why Vinauger initially figured that soap might deter mosquitoes from flying in for a sip.
The story ended up being a bit more complicated. The researchers, led by Morgen VanderGiessen and Anaïs Tallon, collected chemicals from their volunteers’ arms—one scrubbed with soap, the other left aromatically bare—and offered them to the mosquitoes. One body wash, a coconut-and-vanilla-scented number made by Native, seemed to make a subset of people less appetizing, probably in part, Vinauger told me, because mosquitoes and other insects are not into coconut. (Duly noted.) But two other cleansers, made by Dove and Simple Truth, bumped up the attractiveness of several of their volunteers—even though all of the soaps in the study contained plenty of limonene. (None of the manufacturers of the body washes used in the study responded to a request for comment.)
No single product was a universal attractant or repellent, which probably says more about us than it does about body wash. A bevy of lifestyle choices and environmental influences can tweak an individual’s unique odor profile; even identical twins, Torto told me, won’t smell the same to a mosquito on the prowl. Soaped up or no, some people will remain stubbornly magnetic to mosquitoes; others will continue to disgust them. This makes it “hard to say, ‘Hey, this soap will make you really attractive’ or ‘That soap will keep mosquitoes completely away from you,’” says Seyed Mahmood Nikbakht Zadeh, a chemical ecologist and medical entomologist at CSU San Bernardino, who wasn’t involved in the study. Plus, soap is hardly the only scented product that people use: Whatever enticing ingredients your body wash might contain, Tallon told me, could easily be counteracted by the contents of your lotion or deodorant.
The point of the study isn’t to demonize or extol any particular products—especially considering how few soaps were tested and how many factors dictate each individual’s odor profile. The five volunteers in the study can’t possibly capture the entire range of human-soap interactions, though the researchers hope to expand their findings with a lot of follow-up. “I wouldn’t want the public to be alarmed about what type of soap they’re using,” Torto told me.
But just knowing that personal-care products can alter a person’s appeal could kick-start more research. Scientists could design better baits to lure skeeters away from us, or develop a new generation of repellents using gentle, plant-based ingredients that are already found in our soaps. “DEET is really efficient, but it’s a chemical that melts plastic,” Vinauger told me. “Could we do better?”
The researchers behind the study are already trying. After analyzing the specific chemicals in each of the soaps they tested, they blended some of the most alluring and aversive substances into two new concoctions—a flowery, fruity attractant and a nuttier repellent—and offered them to the insects. The repellent was “as strong as applying DEET on your skin,” Vinauger told me, “but it’s all coming from those soap chemicals.”
What’s not yet clear, though, is how long those powers of repulsion last. Most people don’t manage more than a daily scrub; meanwhile, “the odors coming out of your pores are continuously coming out, so in the long run, those might win out,” says Maria Elena De Obaldia, a neurogeneticist who previously studied mosquito attraction at Rockefeller University. And it’s a lot less practical to ask someone to shower every few hours than to simply reapply bug spray.
I’m certainly not ready to blame my mosquito magnetism on my body wash (which, for what it’s worth, contains a lot of “coconut-based cleanser”) or anything else in my hygiene repertoire. Part of the problem is undoubtedly just me—the tastiest of human meat sticks. But the next time I shop for anything scented, I’ll at least know that whatever wafts out of that product won’t just be for me. Some pest somewhere is always catching a stray whiff.
Katherine J. Wu