Why mosquitoes find you irresistible: The science behind their deadly attraction
An anopheles mosquito. The female anopheles mosquitoes are responsible for malaria transmission. PHOTO | FILE
What you need to know:
- We humans often unknowingly make ourselves irresistible targets for mosquito bites.
Mosquitoes don’t target everyone equally, some people are irresistible snacks, while others get ignored.
The ordinary choices we make daily, from what we drink to what we wear, might be sending powerful signals to these deadly insects, turning us into their next blood meal.
If you’re always getting bitten, drinking beer, wearing dark clothes, skin bacteria, sweat, genetics and carbon dioxide are some of the things making you a mosquito magnet, says Dr Willis Akhwale, the senior advisor at End Malaria Council (EMC).
A study conducted in 2002 by researchers from Toyama Medical and Pharmaceutical University found that just drinking 350ml of beer could make an individual more attractive to mosquitoes because alcohol increases one’s body temperatures, causing them to sweat more, thereby attracting the parasites.
The peer-reviewed study involved 12 men and a woman according to researchers. Thirteen volunteers (12 men from 20 to 58 years old and a 24-year-old woman) were chosen as test hosts and a 3O-year-old man was established as a control.
“We measured ethanol content in sweat, sweat production, and skin temperature before and after ingestion of 350 ml of beer (ethanol concentration 5.5Vo) by volunteers and compared them with a control subject.
Our study demonstrated that percent mosquito landing on volunteers significantly increased after beer ingestion compared with before ingestion, showing clearly that drinking alcohol stimulates mosquito attraction,” they observed.
However, ethanol content in sweat and skin temperature did not show any correlation between alcohol ingestion and mosquito landings.
“This study shows that persons drinking alcohol should be careful about their increased risk to mosquito bites and therefore exposure to mosquito-borne diseases,” the scientists concluded.
The study was published by the Journal of the American Mosquito Control Association.
“Also, the carbon dioxide that bubbles out from a beer bottle or can, once opened, could be an additional draw,” says Dr Akhwale.
He adds that mosquitoes can detect the trail of carbon dioxide we breathe out from approximately 30 metres away.
“A high concentration of carbon dioxide may indicate the presence of a victim, and so the more carbon dioxide one emits, the more attractive a target they become,” Dr Akhwale tells Nation, adding: “Larger people give out more carbon dioxide than smaller people, which is why mosquitoes tend to bite adults more than children. The same applies to pregnant women, who are twice as likely to get bitten since they exhale 21 per cent more carbon dioxide.”
He explains: “Forget the myths. Those whining insects aren't just serenading you for fun, they're hunting.”
Your blood
While mosquitoes primarily survive on plant nectar, female Anopheles mosquitoes need something more potent for reproduction: your blood. They require blood meals—not just once, but multiple times—typically feeding twice with one to two days between meals to successfully develop their eggs.
This repeated feeding creates the perfect transmission window for malaria parasites that are transmitted to humans.
Through evolution, these efficient disease vectors have developed a strong preference for human blood over animals like cows, pigs, dogs, or chickens, making humans their favoured hosts and central to the malaria transmission cycle.
Despite global scientists working tirelessly to end malaria, Dr Akhwale explains that we humans often unknowingly make ourselves irresistible targets for mosquito bites.
"When you wear dark clothes, it's not that mosquitoes have an impeccable taste in fashion so much that they appreciate classy dark colours," Dr Akhwale points out.
“Mosquitoes are highly visual creatures and tend to be attracted to people wearing dark colored clothing because dark colours stand out more to the parasites, helping them to identify their next victims, which is why putting on light-coloured clothes may help reduce the bites,” the expert tells Nation.
Dr Akhwale, however, observes that mosquitoes are highly attracted to light, and this attraction to ultraviolet light sources is called phototaxis.
“For this reason, it is commonly thought that yellow and red lights will repel mosquitoes. Although these lights do not necessarily act as a repellent, yellow or red outdoor lights will also not attract them,” he says.
This explains why scientists have taken advantage of social and behavioural factors of mosquitoes to come up with solar-powered mosquito trapping systems (SMoTS) for malaria elimination along Rusinga Island in Western Kenya.
Dr Akhwale, who in the last government served as President Uhuru Kenyatta’s advisor on Malaria, also highlights that science has shown that mosquitoes are more attracted to some people than others due to genetics.
“Mosquitoes need our blood protein to make their eggs. In the past, we used to say certain blood groups, but now scientists are looking at DNA variations,” he notes while explaining that there are particular spots on a human being’s DNA that are more or less likely to make them attractive to mosquitoes.
Dr Joel Odero, a research scientist who specialises in vector population biology at Ifakara Health Institute in Tanzania, highlights that aside from carbon dioxide, lactic acid, uric acid and ammonia are also key components in your sweat that make you irresistible to mosquitoes.
“When you go to the gym and sweat profusely, it increases the amount of uric acid and other compounds found in your sweat. That sweat, together with that additional amount of carbon dioxide released when you exercise as well as increased body temperature, makes you an ideal target for mosquitoes,” he tells Nation.
The scientist further discloses that every human being on the planet has approximately a trillion or so microbes that live in his or her skin, pores and hair follicles.
Depending on their environment and lifestyle, he adds, individuals can have different combinations of microbes, and these play a key role in influencing their distinct body odours.
“Scientists have found that only certain groups of microbes appeal to these highly selective mosquitoes, and having large amounts of a few types of these bacteria tends to make you more attractive to mosquitoes.
