08 Agosto 2017 16:10
You and your partner fall asleep. A few hours later, you're woken in the middle of the night by an angry buzzing in your ear. A mosquito. You try to kill it, but the creature dodges your hand like a tiny ninja. And you know what's going to happen next.
Next morning, your partner wakes up unscathed, while your ankles have swollen to twice their normal size thanks to an itchy red ring of mosquito bites. It's not the first time and it certainly won't be the last. So you ask the universe, why do they always pick on me?
Although it may feel like it sometimes, you're not the only one to go through this. An estimated 20% of the population are especially prone to mosquito bites. Here are some of the factors that play a role in making a person irresistible to the insects:
Blood type. Mosquitoes bite us to harvest proteins from our blood. And it seems they prefer one flavour above all others. A study found that in a controlled setting, mosquitos landed on individuals with Type O blood nearly twice as often as those with Type A. People with Type B fell in the middle of the spectrum.
Carbon dioxide. These insects locate their targets by smelling the carbon dioxide emitted in their breathe. Therefore, people who exhale more of this gas – usually larger individuals – are more likely to attract mosquitoes.
Exercise and metabolism. Another way mosquitoes have of tracking their prey is by smelling the lactic acid, uric acid, ammonia and other substances expelled via sweat. Exercise increases the build up of lactic acid and body heat, while genetic factors influence the amount of uric acid emitted by each person.
Skin bacteria. Other research suggests that the type and volume of bacteria that naturally live on human skin has an effect on how attractive we are to mosquitoes. One 2011 study discovered that skin with large amounts of a few types of bacteria was more appealing to the insects.
Beer. Just a single bottle of beer can make us delicious to mosquitoes. Researchers used to believe that this was due to the increases in body temperature and ethanol excretion that occur when we drink alcohol, but a recent study found no correlation between these two factors and increased mosquito bites, meaning the creatures' fondness for drinkers is still a mystery.
Pregnancy. Several studies have revealed that pregnant women are twice as likely to wake up with mosquito bites. The reasons for this are clear: an expectant woman exhales more carbon dioxide and generates greater body heat.
Clothing colour. According to entomologist James Day, mosquitoes also use vision to locate victims, so wearing clothes that stand out (red, dark blue or black) makes us easier for them to spot.
Genetics. It is estimated that genetic factors account for 85% of the variability between individuals in their attractiveness to mosquitoes. Unfortunately, changing our genes isn't quite as easy as changing our T-shirts.