We’ve all had that friend who never seems to be bothered by mosquitoes even when the rest of the crowd is being eaten alive. While research has accounted for some aspects of why certain people are more appealing than others to annoying bugs, new research out this week has found hints that how delicious you seem to a mosquito may have to do with your genetic makeup.
What attracts mosquitoes to bite?
You’ve probably heard a lot of rumors about what makes a person more attractive to mosquitoes. Some people say eating garlic can help (it doesn’t) or that drinking beer will repel them (it actually attracts them). Research has shown that mosquitoes hone in on CO2, the gas that we release when we breathe and produce as part of our natural process of metabolism. While people who weigh more tend to make more CO2 and are more attractive to mosquitoes, people who weigh the same still see differences in the mosquito appeal.
Researchers had deduced that something else had to play a role in differentiating between different individuals, which is probably the scents we give off. Each person has a unique body odor influenced by a variety of factors. Food can play a role in body odor as prior studies and common experience have found. The problem is diet changes on a daily basis, which means body odor based on food also changes too often for mosquitoes to reliably learn to hone in on that signal. If they just went by food odor, mosquitoes would never reliably find their meal.
Where does human body odor come from?
Little is still understood about just what makes up the scent that a person carries with them. While scientists originally thought that these smells were generated by glands in the skin, new research has shown that bacteria play an important role in determining what a person smells like. Bacteria consume chemicals produced by the skin and then release their own smelly chemical byproducts.
But researchers still don’t fully understand those reactions. The skin probably both produces compounds to be used by bacteria and its own scented chemicals. On top of that, the types of chemicals secreted by the skin for bacteria likely vary from person to person and the types of bacteria on the skin change between individuals. The mosquito team wondered whether genetics might play a role in determining scent by guiding what sorts of compounds the skin makes.
How did the researchers test the importance of genetics?
To separate out the influence of genetics, the researchers compared identical twin siblings to non-identical twin siblings. Since identical twins have exactly the same genetic makeup and non-identical twins have different genetic makeup, mosquito bite differences between to the two groups could be chalked up to genetics. To perform the experiment, the researchers set up a Y-shaped tube. At each branch of the Y, a person could stick their arm in. A mosquito would then be released from the stem of the Y and could travel down the tube to pick the arm it liked the best.
The researchers tested three settings:
- Open air on both sides as a control to make sure mosquitoes didn’t prefer one side to the other.
- Twin A or Twin B if each pair alone compared to open air to make sure mosquitoes were attracted to the arm.
- Twin A compared to twin B of each pair to see which arm the mosquito found more attractive.
With each test, the researchers used a different set of mosquitoes and looked to see which part of the tube mosquitoes spent most of their time and who they ended up choosing to bite.
What did the researchers find?
The team found that the mosquitoes tended to prefer one person when non-identical twins competed for attention, but that the choice was pretty close to 50:50 when the identical twins both offered their arms. That meant the mosquitoes were picking up on some sort of a scent difference between non-identical twins that wasn’t present for identical twins. Since the major difference between non-identical and identical twins is genes, the researchers deduced that genetics must be playing a role in how a person smelled to a mosquito that made them more or less appealing.
How does this affect me?
The team points out that they don’t yet know exactly what genes are playing a role and what compounds are responsible for more attractive smells. But their research offers a clue that could help other teams parse out what genes are responsible and which chemicals make some people more attractive than others. That could lead to better insect repellents and more effective ways to prevent infections like malaria and dengue fever that mosquitoes can pass to unsuspecting victims.