Why mozzies bite some more than others
While summer brings with it days on the beach and nights outside enjoying the balmy weather, another, more unpleasant summer fixture also comes out in droves: mosquitoes.
Although some of us dread being covered in itchy bites, there are others who mosquitoes seem to ignore - and now scientists have part of the answer explaining why.
Researchers from Rockefeller University have found that mosquitoes are attracted to people based on the smell of their skin, created through a blend of particular acids.
Focusing on Aedes aegypti, the mosquito which carries viruses such as dengue, yellow fever and Zika virus, the team used samples of human forearm odour collected on nylon stockings from 64 people, performing more than 2300 tests over 174 days across a three-year study.
They found that people who were highly attractive to the mosquitoes had significantly higher levels of carboxylic acids which contribute to their skin odour.
These carboxylic acids are produced when bacteria on the skin breaks down steroids and cholesterol secreted by our sweat glands.
"We tested mosquito attraction to human skin odour and identified people who are exceptionally attractive or unattractive to mosquitoes," they wrote.
"Chemical analysis revealed that highly attractive people produce significantly more carboxylic acids in their skin [than others]."
They also noted that there weren’t any chemicals found in higher levels on the skin of less attractive people and argued that this supports the idea that people’s skin lack attractive odours, rather than emitting an odour that repels mosquitoes.
As for why some people have higher levels of these chemicals in their skin odour than others, the researchers suggested that genetics may play a role.
"Understanding why some humans are more attractive than others provides insights into what skin odorants are most important to the mosquito and could inform the development of more effective ... repellents," they wrote.
The study, published in the journal Cell, isn’t the first time scientists have attempted to understand why some people are more attractive to mozzies than others - and there are plenty of reasons why.
Mosquito researcher Dr Cameron Webb from the University of Sydney told the ABC it could be to do with genetics, as well as your temperature, your diet, whether you’re sweaty or even whether you’re pregnant.
Dr Gordana Rasic, a senior mosquito research officer at QIMR Berghofer Medical Research Institute in Queensland, explained that the factors driving the behaviour of mozzies are “very complex”.
"Mosquito brains are small but they still process signals from hundreds and hundreds of different receptors," she said.
"Biting humans is specific to female mosquitoes — they need to bite humans and take blood in order to develop their egg and basically reproduce — so it's an absolutely essential instinct."
While this study adds a new piece to the puzzle of mozzie behaviour, Dr Webb noted that this study focused on one mosquito species out of thousands of species around the world.
"Even if you solve the problem for one mosquito, that doesn't mean the relationship and their willingness to bite people applies to all of the mozzies," he said.
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