Scientists reveal why some people are mosquito magnets – and how to avoid the pests
SOME people are mosquito magnets who are plagued by agonisingly itchy bites.
But others seem to get off near enough unscathed, enjoying a summer free from the pesky insects.
New research is starting to show why.
The team at Reactions, a series run by the American Chemical Society (ACS), said on YouTube: “If you feel like mosquitoes flock to you over everyone else at the BBQ, you’re not imagining it.
“Some of us really do attract mosquitoes more than others, based on the chemicals exuded from our skin.
“What are they, how did scientists figure it out, and how can you outsmart them anyway?”
Presenter Alex Dainis, a science communicator with a PhD in genetics, explained that it begins with several broad sensory clues.
First, the pests hone in on our body heat. Then they follow the scent of CO2 from our breath before finally clocking eyes on us.
This clears up how they locate humans in general, but what makes them chomp down on certain people?
Alex, who attended Stanford University in California, said: “I swear there can be eight people at a BBQ and every single mosquito makes a bee line to me like I am their personal BBQ.
“If you’re the same, you’re not imagining it as there really is something that makes us more attractive to mosquitoes.
“It’s skin odour. There have been lots of studies over the years to figure out what makes some people smell so much more delicious to some mosquitoes than others.
“Some studies say that blood type is involved, others indicate that what food or drink you consume might play a role.
“Some say that pregnancy might impact mosquito attractiveness, and then there are other studies that say the presence or absence of malaria infection might impact whether or not they want to bite you.
“But different studies have all shown different magnitudes of effects and conflicting results, so it is confusing – until now.”
Alex pointed to one study published in the journal Cell in October last year.
It looked at fatty acids on our skin, specifically carboxylic acids that we exude in our sebum – the waxy, oily substance that helps keep our skin moisturised.
“This study was amazing,” Alex said.
“The researchers had participants wear fashion-forward nylon stockings on their arms to collect their sebum and then set up a chamber where aedes aegypti (yellow fever) mosquitoes could choose between differently scented nylons.
“And the choice was strong. Those of us who are mosquito magnets, we truly are magnetic to them because they chose our scent way more than others.
“Researchers found that there were several different carboxylic acids that showed up more on the skin of strong attactors than the weak.
“Specifically, the strong attractors produced significantly higher levels of pentadecanoic, heptadecanoic and nonadecanoic.
“And because the study was done over the course of three years, they were able to show it wasn’t something variable, like what food the participants had eaten or whether or not they had had a beer recently. These were stable attractants.”
I swear there can be eight people at a BBQ and every single mosquito makes a bee line to me like I am their personal BBQ.
Alex Dainis
Alex said the reason these acids were so different between the participants could be down to several factors.
“We each might be genetically predisposed to produce slightly different skin compounds, and the differences in our skin microbiomes might also influence the fatty acids that are present,” she said.
But another study in Current Biology in May 2023 provided further insight.
This time looking at anopheles gambiae, another common mosquito species, it studied the body odours from six different people.
Scientists put the mozzies in a big, caged outdoor arena with little pipes leading away to tents housing the participants.
“They once again found that carboxylic acids were big differentiating factors between attractive and non-attractive human scents,” Alex said.
“But this time they found butyric, isobutyric and isovaleric acids leading the pack for most attractive.”
Interestingly though, they also found that the least-preferred subject had an abundance of eucalyptol in their body scent.
“Yes, that sounds like eucalyptus because that’s the main component of the oil,” Alex added.
“The compound likely came from plant-based foods and flavourings in their diet – like bay leaves, mint and rosemary.
“This is just one person, so it’s just a hypothesis, but could eucalyptol in diets help keep mosquitoes away? Maybe.”
DEBUGGED
So how can people plagued by bites try to defend themselves with this knowledge?
Alex said: “You might know that DEET is a big mosquito deterrent.
“It is the chemical compound N,N-diethyl-meta-toluamide and basically it makes it harder for mosquitoes to smell us.
“But what about repellents derived from nature? Things like citronella candles that everyone has on their porches in the summer.
“Do they work? No. A 2017 study found that citronella candles really made no difference at all.
“What did work, was oil of lemon eucalyptus (OLE).”
So it could be possible to ward off mosquitoes with the oil – either with shop-bought repellents and traps, or those made at home.
Several products containing OLE are available on the high street, including one from Decathlon for £7.99 and another by the brand Repel, available on Amazon for £16.
Previous research shows using coconut-scented products in the shower could also be beneficial, while Dove or Simple Truth could make you a magnet.
Reactions is a video series produced by the ACS and PBS Digital Studios.
What happens when a mosquito bites?
WHEN a female mosquito lands on you, it inserts its proboscis into you.
This is a tiny mouth hole of six needles that saw their way into your skin.
Two of the needles are serrated like a saw blade, but the proboscis is formed in a way to minimise pain so you don’t immediately swat the mosquito off.
There is a soft part that hits you first and then the sawing action is combined with a light vibration, so that less force is required.
Some scientists are actually trying to design similarly-shaped micro-needles for more painless injections.
Mosquitoes don’t just suck your blood. They actually inject some of their saliva into you as well.
And while scientists are still trying to tease apart exactly which chemicals in the spit do what, some of them seem to act as numbing agents to keep you from noticing you’ve been bitten.
Others seem to act as vasodilators and anticoagulants, keeping your blood vessels open and your blood from clotting.
There are over 100 proteins in mosquito saliva, and not all of their functions are even known yet, but we do know that that cocktail of chemicals is why we get itchy.
So your body actually has an allergic reaction to mosquito bites.
Your immune system recognises the proteins and starts up a histamine response.
This brings white blood cells to the area, and also activates other immune tools that cause itchiness.
Source: Reactions