by Macy Osborne-Frazier
As summer approaches, many different types of bugs will begin hatching from their eggs and exiting hibernation, including the infamous mosquito. You’ve probably wondered at least once why mosquitoes like to bite us. And if you are especially unlucky, you might have wondered why mosquitoes seem to like to bite you more than other people. If you’ve ever thought this, you’re not crazy! Although we don’t fully understand why, scientists have shown that mosquitoes do find some people tastier than others.
Before we dive into mosquito’s taste preferences, we first need to understand why mosquitoes even bite humans to begin with. Mosquitoes have a long, special mouth called a proboscis, which they use to feed on nectar and to bite humans and other animals. When a mosquito bites you, it uses its proboscis to suck up some of your blood. Interestingly, only female mosquitoes feed on blood. Male mosquitoes only need nectar from plants to survive. So why do female mosquitoes act like vampires? Just like a lot of strange phenomena in nature, it’s all about reproduction. Producing eggs requires more protein than a female mosquito can naturally produce or get from plants, so female mosquitoes use the proteins in human and animal blood to help them develop eggs. That’s right, humans are the ultimate protein shake for a female mosquito trying to grow eggs.
Figure 1. Mosquito with proboscis (Image Source)
Unfortunately for humans, the only thing we get out of an interaction with a mosquito is an itchy, red bump. This is because mosquitoes also leave behind some saliva when they bite us. Our body recognizes mosquito saliva as a foreign substance and sends our immune system to check out the situation. Since mosquito saliva is a substance that is not normally found in our bodies, our immune cells will likely launch an attack on the saliva. Our immune cells often release a chemical called histamine when they encounter mosquito saliva. Histamines are responsible for allergic reactions ranging from typical seasonal allergies to deadly anaphylactic reactions. Luckily, in the case of mosquito saliva, the reaction is typically small and confined to the area of our body where the mosquito bite occurred. The small dosage of histamine in response to mosquito saliva is what causes the bite area to become raised, red, and itchy. Although not all people have an allergic response to mosquito saliva, most people do. The amount of histamine released in response to mosquito saliva dictates how severe the reaction will be. This is why some people seem to have worse reactions to mosquito bites than others.
Even though we all react uniquely to mosquito bites depending on our immune system, all humans have nutritious blood for female mosquitoes. So why do mosquitoes find some people tastier than others? To locate their next meal, female mosquitoes sniff out a chemical called carbon dioxide that is naturally found in your blood, breath, and sweat. Carbon dioxide is a waste product of our metabolism, which means the higher our metabolic rate, the more carbon dioxide we produce. For instance, somebody who is actively exercising will be producing more carbon dioxide than somebody who is sitting still. Therefore, a person out for a run might attract more mosquitoes than a person sitting down for a picnic. In addition, pregnancy causes an increase in metabolic rate, so a pregnant woman out on a walk might be bitten more than she did before she became pregnant. Carbon dioxide isn’t the only thing that makes us attractive to mosquitoes though. A study using twins showed that identical twins (twins with the same DNA) attract a similar number of mosquitoes compared to fraternal twins (twins with different DNA). Even though we don’t fully understand what in our DNA codes for attractiveness to mosquitoes, the results of this study show that our unique DNA can also influence how many mosquito bites we get.
Figure 2. Illustration of mosquito attractants (Created by author with BioRender.com)
For most people, mosquito bites are simply a nuisance, but mosquitoes are known to transmit life threatening diseases in some parts of the world. Learning what attracts mosquitoes is an example of how understanding science can increase quality of life and limit the spread of disease. If we can better understand what attracts mosquitoes, we can create mosquito repellents that could save lives through limiting disease transmission.
