Why mosquitoes love to bite you — and what to do about those pesky bites

A hot and rainy summer is the perfect climate for mosquitoes. Sometimes we’re swatting them away but most of the time, it’s too late. They’ve taken a bite, left their mark and we’re scratching for days.

Have you noticed that mosquitoes are more drawn to you than others while you’re out hiking, camping or lounging in your backyard?

“There’s no doubt that they have a preference but we haven’t figured out what it is exactly. We know that some factors are out there but we don’t know the factors well,” Dr. Carl Lowenberger, a biology professor with decades of experience in studying mosquitoes and parasites at Simon Fraser University, told Global News.

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Global News asked experts why some of us seem to be more vulnerable to mosquito bites than others. There are urban myths aplenty, so we’ve tried to sift through fact and fallacy.

Your blood type

Some people swear they have sweet blood that draws mosquitoes in. Research suggests that mosquitoes are attracted to the taste of type O blood.

“They say type O is fed upon more frequently but I don’t know,” Lowenberger said.

The evidence is spotty, so Lowenberger suggests this may not hold much merit.

You’re sweating

This theory holds more weight, according to Lowenberger. Mosquitoes have very poor vision and first see us by silhouette. After that, their odour receptors kick in.

And while their eyesight is poor, their sense of smell more than compensates.

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On us, they sniff out the sweat, heat and carbon dioxide we breathe out. It’s especially the case if we’ve had a sweaty day of exercising, hiking or we’re wearing the same clothes out during a camping trip, Lowenberger said.

“Then they come close to you and they just go nuts,” Lowenberger said.

You’re pregnant

A 2002 study warned that women in their later stages of pregnancy exhale more – and in turn, churn out more carbon dioxide than women who aren’t expecting.

They guessed that’s why pregnant women were bitten twice as much.

Lowenberger isn’t sure about this either. He suggests it may come down to pregnant women sweating more and emitting more heat. Hormonal changes in pregnant women can also be at play.

Those with diabetes and high blood pressure are off the hook. There’s been no conclusive research that pegs these chronic conditions to being tastier targets for mosquitoes.

Your diet

So far, studies haven’t been able to link any relationship between certain foods attracting or repelling mosquitoes. Some people swear that bananas lure mosquitoes in.

“Some people argue you shouldn’t eat certain fruits or vegetables or eat garlic,” Lowenberger said.

Garlic excretes compounds through our kidneys and out through urine. You’d have to consume a lot of garlic to get to concentrations so high, it would be secreted through the skin.

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“You’d have to eat so much garlic that you’d have no friends. You’re better off rubbing garlic oil on your skin,” Lowenberger said.

“There are no good studies to correlate a link at all,” Dr. Sandra Hong said. She’s an allergist and practicing physician at the Cleveland Clinic.

One study did note that alcohol, such as beer, seems to attract insects, Hong said. Lowenberger suggests that those who drink may end up sweating and emitting more heat.

But, overall, these bloodsuckers don’t discriminate. Across the board, carbon dioxide, sweat and heat seem to be the trifecta for attracting mosquitoes.

“If you’re a warm body, they’ll bite you,” Lowenberger said.

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4:24 Making mosquito season easier

What should you do if you’ve been bitten?

For starters, it’s only female mosquitoes that bite mammals. The insects thrive on sugar so they normally tap plants for sap, for example. But the females need protein so they use a modified part of their mouthpiece to pierce the skin and take blood. The protein from our blood is used to form eggs.

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The process can take between 30 seconds and two minutes. There are one thousand microlitres in a millimeter. A mosquito draws only three of these minuscule units.

We usually don’t feel the bite because mosquitoes add a local anesthetic. But it’s the bug’s saliva — meant to prevent the blood from coagulating when she sucks it up — that causes the bite to flare up.

“Your body tries to isolate the area where the saliva is and that’s how you get a bump where the mouthpiece went in. Your body isolates the area and brings in immune machinery to wipe out the saliva so the area is walled off,” Lowenberger said.

Our bodies develop an inflammatory response and the more we scratch, the more inflamed it becomes, Hong said.

“It can become a vicious cycle,” she told Global News.

Can we protect ourselves from mosquito bites?

Public health officials say that people should avoid the outdoors at dawn and dusk when mosquitoes seem to be on the prowl.

Other studies suggest wearing light clothes, but Lowenberger isn’t sure if that works.

Some experts even recommend showering or rinsing away sweat, or changing out of dirty clothes.

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Your best bet is DEET, a chemical spray that can confuse mosquitoes’ olfactory receptors and throw them off. They may be near you, but they won’t necessarily bite.

Lowenberger reminds Canadians that we could have it a lot worse.

“For us in Canada, it’s a nuisance but in other parts of the world, they represent a potential parasite and potential death,” he said, noting that some of the bugs carry malaria and even Dengue virus.

carmen.chai@globalnews.ca
Follow @Carmen_Chai