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How to Know a Person is a must-read for anyone looking to deepen their relationships and broaden their perspectives—and I believe it has the power to make us better friends, colleagues, and citizens.

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The nose knows

Could perfume be our secret weapon in the war on mosquitoes?

Mosquitoes use their sense of smell to find new victims. A Swiss fragrance company is hoping to thwart them.


Are you a mosquito magnet? If you don’t seem to get your unfair share of mosquito bites every summer, chances are you know someone who does. Some people are just more attractive to the pests than others.

The reason why is probably how you smell. Mosquitoes rely on their sense of smell to find their targets, and they’re drawn to certain odors naturally produced by the human body. Although some people may be a little more attractive, the unfortunate truth is that we all smell like a delicious meal to mosquitoes. You can hide yourself for a while using a bug spray like DEET or treating your clothes with permethrin. But if you want sustained protection, you have to add another step to your routine, which not everyone has the time to do or can afford.

There’s good news on the horizon, though: A company called dsm-firmenich is working to make repelling mosquitoes as easy as washing up in the morning.

I actually visited dsm-firmenich’s lab in Geneva back in 2016, when I checked out their innovative work to improve sanitation for the world’s poorest by reducing toilet odors. The nutrition, beauty, and health company is one of the world’s largest manufacturers of flavors and fragrances. Most of their products are used to make our food taste better and our household products smell more appealing, but they also have a history of using their scent expertise to fight disease transmission. Their latest efforts are focused on stopping mosquitoes, because the diseases they carry kill hundreds of thousands of people each year, most of whom are children in low-income countries.

The team’s goal is simple: Incorporate scents that repel mosquitoes into everyday products. After doing extensive research into the household products used most frequently in places where mosquito-borne diseases are common, they decided to focus mostly on bar soap and powdered laundry detergent. (They’re also thinking about other things like body lotion and body cream.) These products are already scented with a fragrance—what if that fragrance also helped keep mosquitoes away?

The idea is that you gain an added halo of protection without having to add any new steps to your daily routine or buy any new products. No one at dsm-firmenich thinks this kind of protection will be a silver bullet, but their hope is that, when combined with other proven tools like bed nets, people can significantly and sustainably lower their risk of catching deadly diseases like malaria and dengue.

Making a bar soap that gives you all-day protection against mosquitoes is a lot more complex than just infusing it with citronella. The scientists in Geneva started by identifying a wide array of scent ingredients that keep the pests away and are commonly used to create perfumes. Some of these ingredients are true repellants, giving off a smell that causes mosquitoes to fly in the opposite direction. Others block receptors in the mosquito’s brain that usually perceive and draw them to humans.

As they were combining the ingredients to create new fragrances, the team knew they had to keep a human-centered design approach in mind. The best candidates wouldn’t necessarily be the most effective—they also had to smell clean and fresh. I love the smell of cheeseburgers, but I don’t think I’d want my laundry to smell like them every day even if they protected me from mosquitoes!

To test the most promising odors, researchers used a tool I know all too well: The arm-in-cage test, where a human puts their arm—which has been coated in the fragrance being studied—into an enclosed area filled with hundreds of mosquitoes. Sensors track how the mosquitoes respond and whether they’re biting the arm. The team considered any test with two mosquito bites a failure.

Behavioral tests like those being done in collaboration with the Swiss Tropical and Public Health Institute are still ongoing, but they’ve already revealed some surprising results. One of the most effective fragrances so far smells like lily-of-the-valley, a light floral scent that is commonly used in perfumery. It’s exactly the kind of fresh scent that people like in their soaps and laundry detergents. The team’s early results indicate that some lily-of-the-valley odors could be as effective as DEET when used at certain doses.

The next step is the most difficult, and it remains to be seen whether it will succeed. The mosquito experts at dsm-firmenich have handed off the best scent candidates to the company’s product formulation experts and perfumers, who are now looking for ways to make them last all day in consumer products.

It’s a tall order. Scent ingredients are fragile, and activities like scrubbing your hands or washing your clothes cause them to vanish quickly. (Think about how quickly that freshly laundered smell can fade from your clothes.) A perfume that protects you from mosquitoes all day will likely end up being the result of a whole lot of innovation and a complex combination of different scents, rather than one single ingredient. And, of course, the final result has to smell good enough that people are willing to use it every day.

Still, I’m optimistic the scent wizards in Geneva will find a way. The Gates Foundation is supporting their research with the hope that, one day, people in high-risk areas will gain more mosquito protection without having to do any extra work or spend any extra money. When the world gives children and families more tools to protect themselves, we save lives—and take the bite out of the world’s deadliest animal.