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Mozzies, blue cheese and old socks – here’s the buzz!

Why do mosquitoes put the bite on summer fun? Here’s what we know.

It’s a balmy summer evening, you have glass in hand enjoying the waning of the heat of the day. While others are sipping or swilling undisturbed, you’re furiously squatting mosquitos that won’t leave you alone.  

“Why me?”, you groan while reaching for the Aerogard.  

Scientists still don't definitively know the answer to why some people are tastier to mosquitos than others – and they've been doing some pretty out-there experiments to find out.

Our friends at ABC Science put on the repellent in search of some answers.

Dirty socks and Limburger cheese provide clues

Did you know scientists have tested mosquitoes' taste in cheeses and found some species love the smell of blue cheese, while others prefer Limburger? 

In fact, US entomologist Dan Kline took this idea and ran with it back in the 1990s, when he was visited by European colleagues bearing gifts of Limburger cheese. 

"To me, it smelt like dirty socks," says Dr Kline, based at a Department of Agriculture research centre in Florida. 

One day in the lab, Dr Kline pulled off his smelly socks and presented them to the insects. 

"It was the best response we ever saw."

Gross information alert!

It turns out that Limburger cheese contains similar bacteria to those found between our toes, a fact not lost on the monks that originally developed the cheese, Dr Kline says. 

"The monks used their feet in the production of this cheese. Thus, the toe bacteria were involved in the production of Limburger cheese."

The 'smell' of your skin

Mosquitoes are attracted to volatile chemicals we breathe out, or that are produced by bacteria acting on substances produced on the skin, including sweat, and some of these actually seem to protect them from mosquitoes.

Interestingly, one of Dr Kline's colleagues was apparently immune to mosquito bites, and analysis of her skin scents uncovered she was exuding relatively high amounts of a chemical that blocks mosquitoes' sense of smell.

Carbon dioxide and body heat

Even before they get up close to your skin, mosquitoes will be attracted by the carbon dioxide you breathe out — something they can detect at least 10 metres away. Your body heat also helps mosquitoes to zoom in on you. 

"A complex interaction of all of these cues will determine if you get bitten," says Dr Kline's chemist colleague Ed Norris. 

Differences in our genetics, and the cosmetic products we wear also add to the mix, making it a very tricky job to identify what exactly makes someone a mozzie magnet. Plus, much like us, different mosquitoes prefer different scents.

"There are plenty of mosquitoes that are known to be ankle biters or face biters, so there's presumably different volatiles on those different parts of the body that are attracting them," Dr Norris says. 

Finally, your skin's tendency to react to any bites you get may also explain why some people blithely enjoy that outside party, while you don't. They may be getting bitten but not even notice it!

Will eating bananas/garlic/vitamin B make a difference?

Sadly, says medical entomologist Cameron Webb at the University of Sydney, you can't hang your hat on any of these ideas. 

"While some food or drink may subtly change the attraction of mosquitoes, changing diet won't stop you having to use insect repellents," Dr Webb says. 

There's some evidence those with certain blood types are more attractive to mozzies, but Dr Kline says there's conflicting evidence and not enough research to settle the question. 

Are men or women more likely to get bitten?

Males tend to have more of the skin volatiles that mosquitoes are attracted to, but it's hard to generalise. 

There are also studies suggesting pregnant women are more likely to get bitten. This could be because they produce more CO2 and have higher temperatures in the late stages of pregnancy, which may lead to more volatiles being released from their skin. 

Not all mozzies are out to get you

While mosquito-borne diseases are a problem, some species of mosquitoes don't even bite humans. Some prefer to bite animals such as frogs, snakes, birds or even leeches – and there are a small number of mosquitoes that don't suck blood at all.

How to avoid mosquito bites

  • Cover up with long sleeves, pants and covered shoes.

  • Use DEET, picaridin, and oil of lemon eucalyptus repellents (essential oils and other plant-based products need to be reapplied more often).

  • Citronella sticks and candles can help but only if you are sitting close by. 

  • Sit near fans – mosquitoes can't fly in the wind. 

  • Don't bother with sonic devices or repellent wrist bands as they are generally pretty useless. 

  • Remove stagnant water in anything from gutters to pot plant drip trays — mosquitoes only need a millilitre or so of water to breed in. 

Source: ABC Science

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