Why do mosquitoes love some people more than others?

Mosquitoes annoy almost everyone. And sometimes, you might notice that you are getting far more mosquito bites than your friend sitting right next to you in the same room. It can feel unfair, but let’s clear up a common myth first: it is not because your blood is “sweet.”

In reality, mosquitoes do not choose people based on taste at all. Instead, these tiny insects rely on a range of biological signals from the human body to locate their targets. So why do mosquitoes seem to prefer some people over others?

Following the breath: Carbon dioxide

One of the main signals mosquitoes track is carbon dioxide (CO₂), the gas humans release every time they breathe out. Mosquitoes have specialised sensors that allow them to detect CO₂ from several metres away, helping them locate potential hosts even in the dark. People who exhale larger amounts of carbon dioxide tend to attract more mosquitoes. This is one reason adults are usually bitten more often than children. Pregnant women, who produce more CO₂ as their bodies work harder, may also draw more mosquitoes. Similarly, people who have been exercising or have higher metabolic rates can become easier targets. Once mosquitoes detect this invisible trail of CO₂, they begin moving closer to the source.

Heat and movement

Once mosquitoes follow the trail of carbon dioxide and move closer, they rely on other signals to identify their target more precisely. One of these is body heat. Mosquitoes are highly sensitive to temperature and can detect the warmth of human skin, which helps them locate areas where blood vessels lie close to the surface. Movement also makes it easier for them to spot a potential host. A moving body releases more heat and scent into the air, making the signal stronger. Together, these cues help mosquitoes zero in on the exact spot where they can land and bite.

The role of skin bacteria

Another surprising factor lies on the surface of our skin. Human skin is home to trillions of bacteria that naturally live on the body. As these microbes break down sweat and other compounds, they produce a variety of chemical scents. Each person has a unique mix of these bacteria, which means the odours released from our skin also differ from one individual to another. Mosquitoes are highly sensitive to these chemical cues. Research suggests that certain bacterial compositions can produce scents that mosquitoes find especially attractive, making some people more likely to be bitten than others.

What about blood type?

Another common belief is that mosquitoes prefer certain blood types. Some studies have suggested that people with blood type O may attract more mosquitoes than those with other blood groups. However, the evidence is not entirely conclusive, and scientists continue to study this link. More importantly, mosquitoes do not detect blood before they land on a person. Instead, they rely primarily on cues such as carbon dioxide from breath, body heat, and chemical scents from the skin to choose their targets.

The bigger picture: Climate and mosquito spread

A mosquito was found in Iceland — a first for the country. For a long time, Iceland was known as one of the few places in the world without mosquitoes. But scientists have reported sightings in recent years. Mosquitoes generally prefer warmer temperatures to survive and reproduce. As global temperatures rise, conditions in some colder regions are slowly becoming more suitable for them. This expansion raises concerns about the possible spread of mosquito-borne diseases such as Dengue Fever, Malaria, and Chikungunya.