Research suggests that people who get bitten more often may be exhaling more carbon dioxide, generating more body heat or producing certain chemicals as a byproduct of their metabolism. [AFP]
Research suggests that people who get bitten more often may be exhaling more carbon dioxide, generating more body heat or producing certain chemicals as a byproduct of their metabolism. [AFP]

Some people are simply mosquito magnets. Science has confirmed that even in the same place at the same time, certain individuals get bitten far more than others. Entomologists say the amount of carbon dioxide a person exhales, their body heat and the unique odor their skin gives off all determine how attractive they are to mosquitoes.

According to the BBC, only female mosquitoes bite humans. They seek blood — from people or animals — to obtain the protein needed for egg development. Mosquitoes can identify a target from about 10 meters away using sight and smell, and carbon dioxide plays a major role in that process.

When people breathe, they naturally exhale carbon dioxide, which signals mosquitoes' olfactory organs and triggers host-seeking behavior. The more carbon dioxide a person emits, the more mosquitoes they attract. That is why adults, who exhale more carbon dioxide than children, are more likely to get bitten.

Mosquitoes are drawn to carbon dioxide even when it does not come from a person's breath. This property can be exploited to build a mosquito trap — placing dry ice or similar materials in a container will lure mosquitoes in.

Beyond carbon dioxide, heat and moisture also attract mosquitoes. Mosquitoes are drawn to people with higher body temperatures.

Steve Lindsay, a professor of public health entomology at Durham University in the United Kingdom, described the body's metabolic activity as being "like having a small furnace inside you." That means pregnant women, people who are exercising, and larger individuals who generally produce more heat and exhale more carbon dioxide are all at greater risk of being bitten. Pregnancy increases metabolic demand and breathing rate, causing the body to release more heat and carbon dioxide. Exercise similarly raises metabolic demand, warming the body and inducing sweat. Anyone exercising outdoors should be particularly alert to mosquitoes during and immediately after a workout.

Experts advise using proven repellents such as DEET or picaridin and covering exposed skin with long sleeves and pants to reduce the risk of mosquito bites. [AI-generated image]
Experts advise using proven repellents such as DEET or picaridin and covering exposed skin with long sleeves and pants to reduce the risk of mosquito bites. [AI-generated image]

A person's unique skin odor is also a decisive factor in how mosquitoes zero in on a target within 10 meters. Contrary to the popular belief that mosquitoes are attracted to "sweet blood," it is not the composition or smell of blood itself that draws them — it is the odors from skin and breath that trigger their olfactory response.

Lindsay said what mosquitoes use to select a target is "essentially smell," adding that "small, highly volatile chemicals make the difference."

Microbial communities on the skin — including bacteria and other microorganisms — shape a person's distinctive body odor. Researchers at Wageningen University in the Netherlands found that people who attracted more malaria mosquitoes had a richer bacterial community on their skin than those who attracted fewer. Skin bacteria play a key role in producing human body odor; without them, sweat produces no scent that olfactory organs can detect.

This relates to the concept of the microbiome. The skin's microbiome can break down carbohydrates, fatty acids and peptides into volatile organic compounds, or VOCs, which evaporate easily into the air where mosquitoes can detect them. More than 500 organic compounds exist on human skin.

Ammonia and lactic acid have long been identified as skin-derived compounds that attract mosquitoes. Researchers at Rockefeller University in New York have since confirmed that carboxylic acids also play a role. In a study, the Rockefeller team had 64 participants wear nylon sleeves — acting as odor-collection devices — for six hours, then exposed the sleeves to mosquitoes. The insects gravitated toward sleeves with higher levels of carboxylic acids.

Does that mean people who are particularly prone to mosquito bites are simply doomed to suffer all summer? Heather Ferguson, a professor of medical entomology at the University of Glasgow in Scotland, said using proven repellents such as DEET, picaridin or PMD (para-menthane-3,8-diol) can help. PMD is derived from the leaves of the lemon eucalyptus tree. Plant-based repellents sold commercially — such as citronella and lemongrass — tend to be weaker or shorter-lasting. PMD, by contrast, is the only naturally derived repellent ingredient officially recognized as effective by the US Centers for Disease Control and Prevention. Even after applying a proven repellent, protection fades over time and can be washed away by sweat, so reapplication at regular intervals is recommended.

Minimizing physical contact with mosquitoes is another line of defense. Ferguson recommended "covering up with long sleeves and pants treated with insecticide," noting that "covering the body is important because bites tend to concentrate on exposed arms and legs."


kate01@heraldcorp.com