It was a lovely, balmy night. A couple of my friends were sitting outside enjoying a meal as the buttery sun began to set. Suddenly, I could feel something moving on my arm. I knew what it was straight away, and without a second thought WACK! With great satisfaction I looked at my arm: a squished insect and a smudge of blood, the little bug-ger got me already. I whined with disgust, mosquitoes always get me. My mate offered a friendly suggestion: “You should eat bananas, it repels mosquitoes.” Really? I wondered. Does it?
While I am more than happy to chug down bananas any day of the week, I’d rather not be under some impression that I’ll be saved from the wrath of the mossy, if it just ain’t true. After checking the facts about this myth – it seems that reality bites.
Meet the mossy
Our mini rival weighs about two milligrams. And while they are simply annoying little critters to the Western World, mosquitoes are responsible for millions of deaths worldwide. Their bite can carry lethal diseases, such as malaria, dengue, and West Nile encephalitis. Consequently, mosquitoes have been dubbed the world’s most dangerous animal.
Only female mosquitoes need blood because they use it to feed their eggs (mosquitoes’ mainly get their nutrients from plant nectar). As a result, it’s only female mosquitoes that are attracted to humans. Human attraction is also specific to different mosquito species, which is why in some areas of the world you might be a mossies favourite meal, but in other regions they glide right past you – ready to bite a neighbouring cow or donkey.
Why are mosquitoes attracted to humans?
It’s all in the nose. Mosquitoes use smell to find mates, food and blood meals. There are human-specific molecules on your body that give off a particular smell, and mossies can recognise them. These molecules waft through the air until they reach a mosquito, and bind to special receptors on its antennae. When this happens it begins a chemical change in the mosquito, activating their nervous system and alerting them to your presence. Now the mosquito knows who you are, and where you are. Any minute she’ll be on your skin, feeding on your arm. So what are these human specific molecules?
There’s a lot. Carbon dioxide is on the list. IT’s one of the most universally recognized mosquito attractants and can draw in mosquitoes from up to 35 meters. Some compounds in sweat also attract mosquitoes to humans, as do lactic acid, body heat, and odours produced by skin bacteria.
What repels mosquitoes?
Since it’s smell that attracts mosquitoes to human, it’s also smells that repel mossies. Mosquito repellents that can be bought at the supermarket all work by interfere, directly or indirectly, with the mosquitoes’ sense of smell. Some repellents bind to those smelling receptors, which means they are blocked and can’t detect other human specific smells (kind of like a finger up your nose to stop you smelling). Other repellents are just stinky, so the mosquitoes avoid the smell. The most effective, and popular repellent, DEET, might do both; scientists are still debating this one. But onto another debate – do bananas repel mossies?
The Banana Myth
Word on the streets is that eating bananas repels mosquitoes. But the myth isn’t consistent. Others say eating bananas attract mosquitoes. And others still say that it’s not bananas but vitamin B12, which is jam-packed into this fruit, that is making the mossies come our way.
According to the American Mosquito Control Association (a scientific/educational, not-for-profit service), it doesn’t matter what the myth is – they are all wrong. Vitamin B12 has no impact on mosquito biting, and nor does eating bananas. Dr Cameron Webb, an entomologist at Westmead Hospital’s Institute of Clinical Pathology and Medical Research agrees. He says eating vitamin B also won’t help the mossies get off your back.
But there is some new science giving this myth a leg to stand on. A study published in Nature magazine in 2009 from the University of California, noted that mosquitoes have very similar smelling receptors to the Drosophilia fly. And studies in the past have found that the drosophilia avoids smells from a certain chemical found in bananas (3-octanol). This chemical is also found in grapes and strawberries. So, it’s possible that mossies might also be repelled by this chemical as well.
There’s more that needs to be studied. It’s not enough that the smell of bananas repels some mosquitoes – that smell has to waft out of our skin, or breath, or bum, when we eat it.
According to the American Mosquito Control Association, laboratory studies asking people to eat bananas have been conducted, and no repellent action has been found. The only problem is: I couldn’t find these studies! (Can you?)
Okay, so it looks like eating bananas probably won’t affect how attracted mosquitoes are to you. It’s your breath and sweat that is mainly alerting them to your presence. But there is a possibility that some chemicals in food will make a difference. In the meantime, while the experts keep searching for the conclusion, I’d pop on some good old fashion repellent. Just to make sure those mossie bites don’t make you go bananas.
More mosquito matters!
- Why are some people more attractive to mosquitoes than others?
According to Webb, it’s not that people are more attractive to mosquitoes; it’s that some people have a stronger reaction to mosquito bites than others. The itchy red lump from a bite is our immune system reacting to the mosquito’s saliva, and some people have a smaller immune response to the mosquito salivas.
- What’s the best repellent?
Recently investigators at New England Journal of Medicine compared 16 mosquito repellents, including (DEET), soybean oil, and citronella. They tested how effective they were by timing when the first bite took place – after people applied the repellents. Soybean oil was effective for 94.6 minutes. But DEET was best. Only after 112 minutes (almost two hours) was a person bitten when wearing a DEET-based repellent of 6.65% concentration.