Mosquitoes Can Learn to Love Insect Repellant, Scientist Reveal

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Most people aren’t fans of mosquitoes, and for good reason – there are roughly 110 trillion of them around the world, and many spread dangerous diseases like malaria, dengue fever, West Nile virus, and Zika. Surprisingly, new research published in the Journal of Experimental Biology suggests that DEET, a common mosquito repellent, might actually be attracting them instead of repelling them. It seems we’re unintentionally releasing a scent that draws mosquitoes in when we use it.

In 1946, a chemist with the U.S. Department of Agriculture created DEET—short for N,N-diethyl-meta-toluamide—a bug spray that quickly became popular with the military for use in tropical environments. Scientists believe DEET repels mosquitoes by interfering with their sense of smell, making humans and animals undetectable, or by tasting unpleasant to them. It might also work by mimicking the scent of plants that mosquitoes naturally avoid. Whatever the reason, it effectively keeps mosquitoes away—though its effectiveness isn’t always guaranteed.

Researchers, including Clément Vinauger from Virginia Tech, have discovered that mosquitoes, despite being simple insects, can learn. While DEET initially repels them, mosquitoes eventually realize the scent doesn’t last forever. They then start biting again, and surprisingly, begin to associate DEET with getting a blood meal. This means some people wearing DEET may actually attract mosquitoes.

According to Vinauger, mosquitoes are surprisingly intelligent and can overcome methods we use to control them. They can even learn to associate DEET, a common ingredient in insect repellent, with something positive.

Vinauger and his team studied mosquito feeding habits by offering them blood at times when they’re most active – early morning and early evening. In one experiment, mosquitoes were placed near a container of warm blood separated by a fine mesh. They fed on the blood through the mesh, and then were exposed to the scent of DEET, which didn’t stop them from trying to feed. After the blood and DEET were removed, the mosquitoes eventually stopped going to the mesh. However, when the researchers reintroduced only the scent of DEET, over 60% of the mosquitoes returned to the mesh, still expecting to find a blood meal even though the blood wasn’t there.

Vinauger explains that their training showed the subjects could recognize value. Essentially, they learned to see something naturally unpleasant as something appealing.

In the next part of the study, researchers showed two groups of mosquitoes two hands—one treated with DEET and one without. The mosquitoes that had learned to associate DEET with a food source attacked both hands. However, the mosquitoes that hadn’t received this training were only attracted to the untreated hand.

To double-check their results, the researchers ran the experiment again, this time using sugar instead of blood to feed the mosquitoes. Just like with blood, the mosquitoes avoided sugar if it contained DEET. However, if the mosquitoes had previously learned to connect DEET with the sugar, the chemical actually made them more likely to eat it—it signaled a tasty meal was available.

This doesn’t mean DEET isn’t still a good mosquito repellent—it can actually be very effective. However, it does suggest we should change how we use it. Instead of applying a lot at once and hoping it lasts all day, Vinauger recommends using the amount listed on the DEET bottle’s instructions, and reapplying it throughout the day. This keeps a consistent level of repellent on your skin and keeps mosquitoes away.

“It’s the frequency of application, how often you need to put it back on the skin” he says.

While DEET is a common defense, keeping mosquitoes away involves more than just bug spray. Experts suggest using well-maintained window screens and mosquito nets (especially where malaria is a concern). Getting rid of standing water in things like flower pots and kiddie pools helps prevent mosquitoes from breeding. You can also use devices that attract mosquitoes with a scent mimicking human breath and sweat. And, of course, covering up with long sleeves and pants reduces exposed skin. However, recent research suggests that understanding how mosquitoes think might be just as important as avoiding their bites.

Vinauger explains that mosquitoes are surprisingly adaptable, and the more scientists study them, the more intelligent they seem to be.

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2026-05-28 18:06