Mosquitoes Can Smell When Someone’s Had a Beer, and Even Prefer Beer-Drinkers’ Blood

If you’re lounging outside on a muggy night enjoying a beer, you may start to notice wave after wave of mosquitoes pestering you. And it’s not just an unlucky coincidence — it’s because of that brew in your hand.

Mosquitoes don’t just pick people at random to get their fill of blood; they gravitate to certain targets based on a series of factors ranging from diet to the bacteria on our skin. A recent preprint paper uploaded to the bioRxiv server suggests that drinking beer is a surefire way to become a mosquito magnet.

Find out how beer consumption — and a medley of other factors — might make you more prone to mosquito bites.

Read More: This Medication Could Make Human Blood Deadly to Mosquitos, Combatting Malaria

Targeting the Blood of Beer-Drinkers

To see how beer consumption would influence mosquitoes’ attraction to people, the researchers behind the bioRxiv paper got the help of partiers at Lowlands, an annual music festival in the Netherlands. Here, researchers set up a pop-up laboratory inside four connected shipping containers, recruiting 465 volunteers to participate in tests.

The participants first filled out a questionnaire on their general health, diet, and hygiene during the festival. They then placed their arm inside of a cage designed so that the mosquitoes inside could smell, but not bite them. The mosquitoes in the cage could choose between a participant’s arm and a sugar feeder.

The researchers set up a video camera to record how often the mosquitoes chose to land on a participant’s arm, comparing the footage with the questionnaire answers.

They found that those who had been enjoying a few creature comforts at the festival were more likely to be targeted by mosquitoes. Participants who drank at least one beer before the tests were 1.35 times more attractive to mosquitoes compared to those who didn’t have any beer.

In addition, mosquitoes were notably attracted to those who reported smoking cannabis in the past 48 hours, as well as those who slept with someone the previous night.

A Mosquito’s Favorite Smells

So what makes beer-drinkers so attractive to mosquitoes anyway? The researchers note that measured blood alcohol concentration didn’t have an effect on mosquito attraction; they say that it could instead be the distinctive smell given off by those who drank beer.

Humans produce a lot of distinct chemical signals — called volatile organic compounds (VOCs) — that tend to attract mosquitoes, like carbon dioxide, lactic acid, and carboxylic acids.

The amount of these compounds that we release varies from person to person. For example, the rate of C02 release is associated with factors like metabolic rate, body mass, and respiratory activity. Pregnant women seem to be common targets for mosquitoes, which may be caused by an increased release of mosquito attractants (like C02) due to higher metabolic rate and heat production.

Consuming beer likely attracts mosquitoes due to alcohol metabolism changing someone’s body odor. Diet may even influence mosquito attraction in other ways, and while this idea has not been thoroughly explored with many foods and drinks, a 2018 study found that consumption of bananas could modify human odors and entice certain species of mosquitoes.

Keeping Mosquitoes at Bay

While mosquitoes may fancy certain smells, there are a few other factors that help to keep them away. One example is the microbiota living on our skin. Studies have shown that high diversity of skin microbiota correlates to reduced mosquito attractiveness; on the flip side, high abundance, but low diversity of bacteria is associated with increased attractiveness.

In the preprint paper, the researchers noticed that participants who had showered recently and applied sunscreen were less attractive to mosquitoes.

Mosquitoes are also drawn to darker colors, particularly black and red. If you can’t fathom giving up beer any time soon, it may be best to don a pair of clothing with lighter colors — and bring some repellent while you’re at it.

Read More: Mosquitos Carrying West Nile Virus Detected in Massachusetts, Putting Communities at Risk

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