Making the ultimate mosquito repellent

The arrival of summer in the U.S. means Fourth of July parades, picnics, barbecues, camping. It also means the return of something much less pleasant: mosquitoes, ready to suck the blood out of your summer fun.

The good news is safer, better-smelling insect repellent is coming, thanks to recent research: completely in the dark before, we know now what a bug’s nose knows.

Fig. 1 by the University of California on YouTube

“The mosquito has an incredibly sensitive nose,” said Anandasankar Ray, professor in the Entomology Department at UC Riverside and director of the Center for Disease Vector Research. He should know: Ray has spent much of the past decade learning how mosquitoes detect scents.

When we exhale, we emit carbon dioxide. Mosquitoes have super-sensitive CO2 sniffers, and follow plumes of gas knowing that a tasty source of blood is waiting at the other end. The simplest way to keep mosquitoes from finding you is to confuse them by jamming their scent radar.

Most mosquito repellent on the market today contains a compound called DEET, the go-to since the 1950s. It works well, but why it works has long been a mystery. DEET can also melt your swim trunks, cause a variety of negative reactions and is too expensive to be of true value in parts of the world where malaria and other mosquito-borne illnesses are a serious problem.

Ray started wondering why there had been so little innovation around DEET. A cheaper, effective mosquito repellent without the problems associated with DEET could save lives on a massive scale — surely there was something better out there.

“It turns out that DEET is incredibly complex, or rather, understanding how mosquitos detect DEET has been a big challenge,” said Ray.

Ray’s lab at UC Riverside started trying to understand exactly how mosquitos detect DEET. First, they found a receptor in the antennae shared widely among insects that can detect DEET. Once they had located the receptor, they were able to rapidly screen chemical databases for safer and better-smelling alternatives that would work in the same way.

“We were able to very rapidly screen nearly half a million chemicals in one afternoon and identify 1,000 new substitutes for DEET,” said Ray.

Many of these chemicals come from fruits and plants and are already known to be safe for human use — and, as a side benefit, many of them naturally smell fantastic. Instead of a harsh medicinal aroma, imagine having an effective mosquito repellent that smelled like sandalwood or sweet orange blossom.

Mosquitos repelled by SensoryGen compound
Ray's Lab is identifying scents that smell nice, but repell mosquitoes.
Credit: Ray Lab, UC Riverside

For Ray, this is about something much bigger than giving you an annoyance-free picnic.

“Nearly a billion people worldwide are affected by mosquito-borne diseases,” said Ray.

“I am hopeful that this approach will lead to interventions that could be useful in the field and perhaps not only help protect us in our backyard barbeques, but also help have an impact on malaria.”

💡 This research was partially supported by the National Institutes of Health’s National Institute of Allergy and Infectious Diseases (grants R56AI099778 and R01AI087785) and the National Institute of Neurological Disorders and Stroke (grant R21NS074332) and internal funding from UC Riverside. Join UC in asking Congress to protect research funding.