About 20% of the population is more susceptible to mosquito bites than others, and scientists have been working to discover why these poor souls seem to be especially delicious. One of the key reasons? Blood type.

In a controlled setting, mosquitos landed on people with Type O blood nearly twice as often as they landed on people with Type A. (Folks with Type B blood fell somewhere in the middle.)

To make matters worse, about 85% of us secrete a chemical signal that lets mosquitoes know what blood type we have; and the little buggers naturally gravitate toward humans who secrete the chemical, regardless of the person’s blood type. Essentially, if we are Type O and a secreter, we have been hit with a “double whammy”.

Other “risk factors” which can make individuals of any blood type more attractive include pregnancy, exercising, our sweat, and heavy breathing. Mosquitos can detect the carbon dioxide we exhale, from 55 yards (50 m) away, and they will quickly zero in on us. Individual metabolism, clothing color (avoid black, dark blue, and red) and even drinking beer, apparently can also make us more attractive and delicious.

On the plus side, researchers have discovered that some people secrete substances that mosquitos find unattractive. It may be possible, in the future, to incorporate these substances into a bug spray which would theoretically allow a Type O, sweating, exercising, pregnant woman in a black shirt to avoid being bitten.

More Info: www.smithsonianmag.com