Scientists explain how to prevent mosquito bites

For as long as there have been humans, mosquitoes have been buzzing around hoping to get a bite to eat.

“We are always at war, a perpetual war against mosquitoes,” said Dr. Conor McMeniman, assistant professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins Malaria Research Institute in Baltimore.

The science of mosquito bites

Most of the time, mosquitoes drink nectars and juices from plants, and even help pollinate flowers. But when it comes time for female mosquitoes to lay eggs, mothers-to-be need extra protein, which they get by drinking blood.

“When a mosquito bites, it’s sticking its mouth into your skin and probing to find a blood vessel,” McMeniman said. Once it reaches its target, the mosquito sucks up the red blood cells and plasma as if it were drinking bubble tea through a straw.

It is to the mosquito’s advantage to drink it quickly and then disappear undetected. To achieve this, “the mosquitoes spit a whole cocktail of different proteins into the skin” that act as analgesics and anticoagulants that prevent blood from clotting, he said.

The itchiness and discomfort of mosquito bites – the result of our body’s inflammatory response to this chemical cocktail – only emerge later, when the insect is no longer in danger of being scared away.

People have different reactions to mosquito bites – one person might walk away from a barbecue relatively unscathed with a few pimple-like spots, while a friend will need to tend to dozens of bigger bruises over the next week.

“How attractive you think you are to mosquitoes may not necessarily correlate with how attractive you actually are to mosquitoes,” McMeniman said. “Part of that is driven by your perception of your reaction to mosquitoes and whether you’re scratching yourself.”

What attracts mosquitoes?

McMeniman found that some people really are mosquito magnets, and he documented this in his recent study in the journal Current Biology.

Mosquitoes responded differently to the variety of chemicals that make up each individual’s body odor bouquet, and found some more appetizing than others. Unfortunately, figuring out what makes some people extremely attractive to mosquitoes is not a simple matter.

“There can be a variety of factors that can influence your perfume composition, including your underlying diet, genetics and physiology. All of these things could influence the types of molecules emitted by the human body and also influence the composition of the microbiome that naturally lives on our skin,” said McMeniman.

It would be nice to simply replicate the odor profile of people that mosquitoes avoid and sell it as a body spray to those with the dubious honor of being “tastier”, but at this point it’s unrealistic. “We are still trying to understand the chemistry of this process,” he added.

While the details of the smells that attract mosquitoes are still being explored by researchers, there is a general pattern in the insects’ ability to find us.

“First they smell you, then they see you, and then when they’re close enough, maybe three feet away from the host, they can actually detect thermal cues dissipating from your skin.”

One of the most important smells that attracts mosquitoes from afar is carbon dioxide, the gas we exhale when we breathe.

“As a universal, most of them are attracted to CO₂ from a long distance,” said Dr. Kristen Healy, associate professor of entomology at Louisiana State University. “There have been many studies to show that the CO₂ from our breath when we exhale, and especially when you gather large groups.” Body heat and sweat also seem to play a role.