Why do mosquitoes prefer some people over others?

It’s not just luck. Dozens of factors can affect mosquitoes' taste preferences—and make you a better-looking target during your next barbecue. Scientists disagree on the finer aspects of mosquito attraction, but here’s an overview of some of the factors that probably make you especially delicious to the little blood suckers:

  • You’re breathing
    • Female mosquitoes have a receptor that allows them to track carbon dioxide, so every time you breathe out, you’re sending a signal that mosquitoes can detect. Breathe heavily, and you’ll be a bigger target.

  • You’re smelly
    • Even if you stop breathing while outdoors (note: don’t try this), mosquitoes can still track you down. They’re able to learn human body odor, and the same receptors they use to detect carbon dioxide double as scent detectors.

      We know this thanks to a study performed by a team of researchers led by Anandasankar Ray at University of California, Riverside. Ray’s team put mosquitoes in a wind tunnel along with a plate of glass beads; humans had worn socks with the glass beads in them for several hours.

      Next, the researchers exposed some of the insects to a chemical that shut down their carbon dioxide receptors. The mosquitoes exposed to the chemical were less likely to go after the glass beads.

      That’s good news for us, since it means products that block the insects' receptors disable both of the mosquitoes' main tools. The most popular of those products is DEET, which Joe Conlon, technical advisor of the American Mosquito Control Association, described to HealthyWay as “the gold standard by which all repellents are judged.” If you’re getting eaten up in the summer, look for a product with DEET.

  • You’re wearing dark colors
    • Unfortunately, mosquitoes also have decent eyesight, and the strongest repellents on the market can’t blind the insects. Some experts believe that mosquitoes are attracted to darker colors.

      However, that effect is likely minor. As Conlon told CNN, your clothing color probably doesn’t matter too much. With that said, darker colors can make you warmer, causing you to sweat more, and the sweat can certainly draw the little buggers out.

  • You’re warm
    • Mosquitoes can sense heat, which might explain why they tend to go after larger people. The larger the person, the larger the heat signature. In general, the insects prefer adults over children, and a 2000 study found that they prefer pregnant women (we should note that the study had a fairly low sample size).

      While you might not have too much control over your body heat, you can avoid some bites by avoiding overexertion.

  • You’ve got a certain blood type
    • One study published in the Journal of Medical Entomology found that one species of mosquito preferred to target people with Type O blood. That led a bunch of websites to confidently declare that blood type is a major factor in mosquitoes' taste preferences.

      However, the study was later refuted due to poor statistics that didn’t back up its conclusion. Experts like Conlon say that if blood type is a factor, it’s a minor one.

  • You’re trusting mediocre repellents
    • Products like citronella might smell nice, but they’re not very effective at masking human scent.

      “The current [citronella] formulations out on the market give you about one hour of protection,” Conlon said. “And that’s one hour more than you’ll get if you don’t use any type of protection, but I’m afraid it’s far poorer than anything you would get with any of the other [active ingredients] that are marketed.”

      Likewise, natural repellents like clove oil aren’t lastingly effective. If you’re dead set against using a product with DEET, Conlon recommends oil of lemon eucalyptus or refined oil of Nepeta cataria (catnip).

    If you’re getting bit when you spend time around your home, look for areas where mosquitoes are congregating and breeding. Eliminate sources of stagnant water and make sure that your home’s window screens are in good repair. While you might not be able to avoid every mosquito, you can drastically limit your risks—and if you’re constantly itching, the effort is well worth your time.