Mosquitoes in summer: Why do some people get bitten more?

·7 min read
Mosquito bites in summer. (Getty Images)
It's time to get that mosquito repellent out. (Getty Images)

Mosquito bites can really ruin a holiday. They’re unsightly, take forever to disappear and worst of all, itch like mad. But some people are far more susceptible to those pesky bites than others.

You're probably used to hearing your friends and family declare either 'mosquitos love me' or 'I must be immune' during the summer, or perhaps you're the one who's loved or hated by them.

But in these conversations, no one really knows why some people get bitten more than others.

Ready for your next mosquito-filled holiday chat, here are some possible factors to consider...

Colours and clothing

Man wearing red top itching. (Getty Images)
Don't help mosquitoes to see red. (Getty Images)

One study earlier this year found that mosquitoes could quite literally see red, with your outfit and skin contributing factors.

Researchers discovered that a common species of mosquito flies towards specific colours, including red orange, black and cyan.

But they ignore colours like green, purple, blue and white.

The authors believe these findings help to explain how mosquitoes find their 'victims', since human skin, regardless of overall pigmentation, emits a strong red-orange 'signal' to their eyes.

So, while you can't exactly change this part, it seems the colour of your clothes could help deter them.

Read more: UK weather: What happens to your body when it gets too hot?

“One of the most common questions I'm asked is ‘What can I do to stop mosquitoes from biting me?’” said senior author Jeffrey Riffell.

“I used to say there are three major cues that attract mosquitoes: your breath, your sweat and the temperature of your skin.

"In this study, we found a fourth cue: the colour red, which can not only be found on your clothes, but is also found in everyone’s skin. The shade of your skin doesn’t matter, we are all giving off a strong red signature.

"Filtering out those attractive colours in our skin, or wearing clothes that avoid those colours, could be another way to prevent a mosquito biting.”

This knowledge is also hoped to help design better repellants, traps and other methods to keep the pests at bay.

Man and woman running. (Getty Images
Just breathing attracts mosquitoes – but there's nothing we can do about that one. (Getty Images)

The effect of CO2

The same study found, however, that before the mosquito is able to detect colours, they use odours to help them distinguish what is nearby.

"When they smell specific compounds, like CO2 from our breath, that scent stimulates the eyes to scan for specific colours and other visual patterns, which are associated with a potential host (such as us humans), and head to them," says Riffell.

So, first the smell, then the colour. The study also showed that without any stimulant from smell, mosquitoes mainly ignored the coloured dot (used for the experiment), regardless of colour.

While we can't help but emit CO2 when we breathe (which we can't smell ourselves), it could be useful to consider that if we exert more through things like exercise, they could flock to us.

Read more: Hot weather: Why you shouldn't sleep naked

Odour and smell

Speaking on This Morning earlier this month, Dr Zoe Williams said, “Some people potentially have it down to their natural scent. If you sweat more, we know mosquitoes are more attracted to sweat."

She said they might like the perfumes we wear too, so smelling lovely won't exactly help either.

“Lots of people burn citronella (an essential oil) – bad news – they are not actually proven to be that effective," she added.

“But citronella in incense sticks is much more potent so that can be effective.”

One study also showed that mosquitos are more likely to bite people who produce more of certain types of acid such as uric acid, which can also trigger the mosquito's sense of smell.

Blood type

While she acknowledged there "are a number of reasons" that make a mosquito bite more likely, Dr Zoe also pointed out the more commonly known cause. "It’s been said that if your blood type is O negative, then you’re more likely to get bitten," she said.

Research shows that about 80% of people secrete specific compounds and antigens through their skin, which gives away your blood type and lures mosquitoes in. The scent of type O seems to be the most attractive, whereas A (if this is you, you're in luck) is thought to draw them in the least.

Pregnant woman on beach. (Getty Images)
Pregnant women have been associated with more mosquito bites. (Getty Images)

Body temperature

It's also thought the hotter you are, the more appealing you are for mosquitoes, as they can detect heat and water vapour when near us. One study found that they move towards sources, or humans, at a specific desired temperature.

Pregnant women in particular have been found to be more susceptible to insect bites, partly due to their higher temperature, and partly because they exhale more carbon dioxide.

Of course, temperature is linked to sweat, making the chances of attracting them even greater...

Hunting strategy

the mosquito is sucking blood with full blood visible on its body. (Getty Images)
They smell, they see, they feel. (Getty Images)

In terms of how all of these sights and smells work in order, previous research found that mosquitoes track down something to bite using this sequence of cues: smell, then sight, then heat.

"They only pay attention to visual features after they detect an odour that indicates the presence of a host nearby," Dr Michael Dickinson, the study's senior author, told the BBC.

"This helps ensure that they don't waste their time investigating false targets like rocks and vegetation."

The team developed this three-stage hunting strategy:

  • From distances of 10-50m they use smell (particularly CO2)

  • If already aroused by a smell, they will head for something visually interesting (this has a range of 5-15m)

  • Once within one metre of a potential target, they zero in on body heat

"The unfortunate conclusion is that it's very difficult to escape mosquitoes," said first author Floris van Breugel.

"If you were able to capture all the CO2 that you were breathing out, then it'd be less likely that a mosquito would find you. But then if you were in a group of people, and somebody else wasn't taking those precautions, then a mosquito would follow their CO2 plume. And it may end up finding you before it finds your friend.

"So you'd want to be visually camouflaged [as well]. The more of those sensory cues that you disrupt, the less likely they are to find you and bite you."

Read more: Why do I swell up in the heat? 5 ways to reduce oedema this summer

So essentially, while you can't control some of these factors, there are some measures you can take to minimise your risk of being bitten (or intercept the 'hunting strategy').

Full white outfit, anyone?

How to protect yourself

Bites from mosquitoes often cause small red lumps on your skin which are usually very itchy, while some people may also develop fluid-filled blisters.

Mosquitoes don't cause major harm in the UK, but in some parts of the world they can spread serious illnesses such as malaria.

Get medical help right away if you develop worrying symptoms, such as a high temperature, chills, headaches and feeling sick, after a mosquito bite abroad, the NHS advises.

See its website for more information on preventing insect bites and stings, such as using repellents, here.

Watch: Scientists are using dirty socks to understand why some people are mosquito magnets

 

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