Why Mosquitoes Bite

Health Writer

You want to sit outside and enjoy the warm summer night, but you know no matter what you do, chances are you are going to end up going indoors to avoid the mosquitoes. They seem to gravitate to you"and only you. But why?

There are a large number of theories on why mosquitoes bite some people and not others. It has been blamed on the food you eat, your blood type, cholesterol levels, pregnancy and many other reasons. One of the reasons scientists have such a difficult time narrowing down why these insects choose certain people is because there are about 3,000 different species of mosquitoes around the world and about 150 different species in the United States. What makes one species bite isn't the same as what makes other species bite and not all mosquitoes bite mammals.

We do know that only female mosquitoes bite, but not to feed; they need the protein in the blood for their eggs.As she bites, she inserts a small amount of saliva and then draws out the blood. The reaction you get, welts and itching, is an allergic reaction to the saliva.

Mosquitoes probably find you by following the smell of your body and the carbon dioxide you breathe. Then, a number of other factors, such as smell and taste determine whether you are worth biting. Dr. Leslie Vosshall, who has been working to determine exactly why some people are attractive to mosquitoes and others aren't believes the insects go through a process. First, they smell us through the bacteria on our skin and the carbon dioxide. Then, as they move closer, they detect the heat from our bodies. Once they land, they use receptors on their legs to taste our skin. If the mosquito doesn't like what it tastes, it flies away without biting.

Many of the other theories about why mosquitoes bite certain people and not others, can be explained through the main components of attraction of carbon dioxide, body heat and odors. For example, one study showed that women who were pregnant were bit by mosquitoes more often than women who were not pregnant. Those who are pregnant normally give out more carbon dioxide and have slightly elevated body temperatures. There is also a theory that you are bit more often when exercising outdoors than when you are sitting quietly. This also can be explained as when exercising you are panting or breathing heavily and therefore giving off more carbon dioxide. Your body temperature is raised and your sweat also contains lactic acid, uric acid and ammonia, all of which can be smelled by the mosquito.

Other theories, such as what you eat, the color of your clothes and your blood type are under debate. Small studies have shown some association between these things and the amount of mosquito bites but Joseph M. Conlon, an entomologist who works with the American Mosquito Control Association, doesn't believe these things make much of a difference. He points out that a study linking blood type with the amount of mosquito bites was later refuted. The color of your clothing itself doesn't make much difference, however, it may be that you retain more heat when wearing dark clothes and it is the heat that attracts the mosquitoes.

Despite all the theories, scientists believe that genetics play are large role in whether or not mosquitoes are attracted to you, with some scientists putting the genetic link as high as 85 percent of attraction to mosquitoes. If this is true, there isn't much you can do to limit your mosquito bites except to rely on insect repellants that contain DEET.


"FAQ's on Mosquitoes," Updated 2011, Jan 7, Staff Writer, Rutgers University

"Mosquitoes Love Some People More and Science Wants to Know Why," 2013, Aug 6, Josh Dzieza, The Daily Beast

"What Makes Me so Tasty? 5 Myths About Mosquito Bites," 2014, July 4, Sara Cheshire, CNN Health

"Why Do Mosquitoes Bite Some People More Than Others?" 2013, July 12, Joseph Stromberg, SmithsonianMag.com