scientists at Rothamsted Research in the UK discovered that some people produce chemicals that smell bad to mosquitoes, masking the chemicals that usually attract the mosquitos.

You’re trying your best to enjoy an evening cookout, but a constant swarm of mosquitoes follows you from grill to poolside. The threat? A pierce to your skin, leaving behind an itchy red welt and possibly even a serious illness. As you swat madly at the pests, you notice that others seem completely unfazed. Could it be that mosquitoes prefer to bite some people over others?

The short answer is yes. Mosquitoes do exhibit blood-sucking preferences, say the experts. 'One in 10 people are highly attractive to mosquitoes,' reports Jerry Butler, PhD, professor emeritus at the University of Florida. But it's not dinner they're sucking out of you. Female mosquitoes -- males do not bite people -- need human blood to develop fertile eggs. And apparently, not just anyone's will do.

First of all, it’s not in your head. Mosquitoes really do prefer some people to others, says Dr. Jonathan Day, a medical entomologist and mosquito expert at the University of Florida. And that time your grandmother told you your skin was just sweeter? There’s some truth to that, Day says. “Some people produce more of certain chemicals in their skin,” he explains. “And a few of those chemicals, like lactic acid, attract mosquitoes.” There’s also evidence that one blood type (O) attracts mosquitoes more than others (A or B).

Unfortunately, your genes dictate your blood type and the chemical makeup of your birthday suit. Genetics also determine several other factors that could make you an object of blood-sucking affection for your local mosquito population, Day says. Maybe the most important: Your metabolic rate, or the amount of carbon dioxide (CO2) your body releases as it burns energy

Not surprisingly—since, after all, mosquitoes bite us to harvest proteins from our blood—research shows that they find certain blood types more appetizing than others. One study found that in a controlled setting, mosquitoes landed on people with Type O blood nearly twice as often as those with Type A. People with Type B blood fell somewhere in the middle of this itchy spectrum. Additionally, based on other genes, about 85 percent of people secrete a chemical signal through their skin that indicates which blood type they have, while 15 percent do not, and mosquitoes are also more attracted to secretors than nonsecretors regardless of which type they are.

Read more: http://www.smithsonianmag.com/science-nature/why-do-mosquitoes-bite-some-people-more-than-others-10255934/#t0rcXt9pMQQaO705.99 Give the gift of Smithsonian magazine for only $12! http://bit.ly/1cGUiGv Follow us: @SmithsonianMag on Twitter