Everything you need to know about mosquitoes

Why do mosquitoes bite?

First things first, not all mosquitoes bite. In fact, Dr Webb says, there is one type of mosquito in Australia that doesn’t bite humans at all – feeding only on plant juices.

But when it comes to the thirsty little bloodsuckers, only one of the sexes will ever show its teeth.  

“Mosquitoes need blood not just to keep them alive – they also need protein to develop their eggs,” Dr Webb explains. “This is why only female mosquitos bite. A bloke won’t touch you.”

What attracts mosquitoes?

The exact science behind why mosquitoes bite some people and not others is still out, but bug experts say certain physiological factors may influence how attracted they are to you. 

Medical entomologist Scott Ritchie says CO2 is one of the long-range cues mosquitoes use to “locate a host” or, in other words, a feed.

“All vertebrates exhale carbon dioxide so, if you’re breathing, that’s one of the first attractants,” he explains. “You can take a block of dry ice, which is just frozen CO2, and hang it out in the woods, and mosquitoes will come to it.”

You exude CO2 through your breath, but some of it is also emitted through your skin. So, if you’ve just been to the gym, or on a hike, or your breathing is increased, Adj. Prof. Ritchie says you might be drawing more mosquitoes to you.

“From a distance, that’s how they find you,” he says.

Once they’ve located a host, heat, skin temperature and skin chemistry all play a part in helping mosquitoes choose who to feed on. Adj. Prof. Ritchie says the reason mosquitoes respond to people differently is because of the smells produced by different bacteria and chemicals on our skin.

He says there are hundreds of chemical compounds found on our skin and, while diet may change that a little bit, it will never be enough to make us unpalatable to mosquitoes.

“We don’t know exactly which skin compounds they’re attracted to,” he says. “But we know that mosquitoes like heat so they will be more attracted to the person whose skin temperature is slightly higher. "

If you haven’t showered, there will be more bacteria on your skin, which is another way you might be inadvertently making yourself more appetising.

Why do mosquitoes bite your ankles?

There’s a reason mosquitoes often bite your ankles, feet and other peripheral body parts. 

“If you’re a mosquito, one thing you’ve got to be able to do is avoid the slap,” Ritchie says. “The best way to do this, firstly, is to be quick; if they see any movement they’ll fly away. The second is to bite as far away as possible from the slap.”

They often feed on your feet and ankles, Dr Ritchie explains, because it gives them extra time to buzz off when once you realise you've been stung. 

“This is all evolution.”

What can you do to reduce your chance of being bitten?

We can’t change our biology, but there are some things we can do to make ourselves less enticing to mosquitoes. As well as being attracted to certain odour cues, Ritchie says mosquitoes also respond to visual attractants.

“They tend to like dark things,” he says. “If you’re wearing dark clothing and the person next to you is wearing white, you’ll be more attractive.”

And if you’ve ever wondered whether mosquitoes can bite through clothing, the answer is a resounding yes. 

“Wear light-coloured, loose-fitting clothing to avoid being bitten by mosquitoes.”

He says mosquitoes are most active at dawn and dusk so, if you can’t avoid being outdoors at these times, the most effective way to avoid being bitten is to use an insect repellent.  

Does eating certain foods help to repel mosquitoes?

From eating garlic and vitamin B to avoiding potassium-rich bananas, there are countless old wives’ remedies for how to keep mosquitoes at bay. 

But mosquito researcher and medical entomologist Dr Cameron Webb says there’s no scientific evidence that anything you eat or drink, or changes you make to your diet, will stop mosquitoes from biting you.

“These are all myths,” he says. 

There is one very commonly cited study in Africa, he says, where they found that people who drank beer attracted more mosquitoes than people who just drank water. 

“There was a slight but statistically significant finding,” he says. “But that doesn’t mean laying off the booze at your next summer barbecue is going to protect you.”

Can you use sound to repel mosquitoes?

A quick search in your phone’s app store will yield countless results for mosquito-repelling apps that use sound to deter the bugs. While novel, Dr Webb says these are nothing more than a gimmick.

“Ultrasonic sound from your phone is not going to stop you getting bitten by mosquitoes,” he says. “Sound has been marketed for decades but there is just no evidence for it whatsoever. These sonic smartphone apps and battery-operated keychain clips are completely useless.”

The reason this myth pervades, he says, is that there was a really fascinating study by researchers in Malaysia that played dubstep to mosquitoes to see if it stopped them from biting or laying eggs.

“They noticed there was a slight reduction in mosquitoes that were blood feeding and a slight reduction in the number that were laying the eggs,” Dr Webb explains. “Generally speaking – the whole idea of sound as a repellent is not grounded in any kind of scientific theory and there is no real evidence female mosquitoes are responding to sound in any great way.”

Dr Webb says male mosquitoes do respond to sound, which is why they can be bait-trapped with the siren song of the female mosquito. “But female mosquitoes are tone-deaf so playing Skrillex will not protect you from being bitten.”

How can you keep mosquitoes out of the house?

If you’ve noticed mozzies lurking outside your back door, there are things you can do ensure they never make it over the threshold. 

As the weather warms up, Dr Webb recommends doing a sweep of your house – check your fly screens and doors and patch any holes or replace screens that have become loose or damaged. 

If you’ve got any pools of stagnant water around the house, he also suggests removing these so that mosquitoes cannot breed. This could include cleaning your gutters to ensure water is not pooling in your eaves. 

Once they’re inside, the best way to rid yourself of mosquitoes is to use insect sprays and repellents formulated for indoors. “There are also things like strips you plug into the wall that have timed release of insecticides,” he says. 

What is the best insect repellent?

If you’re looking for a tropical strength insect repellent, Dr Webb says there are three key active ingredients you should be looking for on the label: 

• Deet: This is the most common and popular insect repellent.
• Picaridin: This is found in almost as many as Deet and is just as effective, but was specifically designed to be a bit more pleasant to use.
• Oil of lemon eucalyptus (or OLE): This is not as widely available as the other two in Australia, but is commonly available in repellents overseas. Despite what the name might suggest, this ingredient is not the essential oil of a lemon eucalyptus plant – but a bi-product of the distillation process. It has been shown to be almost as effective as the other two. 

There are many theories about why insect repellents work to deter mosquitoes. 

“The key theory is they just don’t like it and fly away,” Dr Webb says. “Another common theory is that they can block the sensory receptors of mosquitoes and interrupt their appetite for blood.”

When it comes to natural alternatives, he says it’s much more about trying to mask or overpower our natural smell to stop the mosquito from biting.

When it comes to repellents, it’s not just the active ingredient, but how you use it that’s important. 

“When you’re applying repellent, you should be applying it the same way as you would sunscreen,” Dr Webb says. “If you miss a bit – mosquitoes will find a way to bite.”

For that reason, Dr Webb says his favourite formulations are usually the liquid pump-pack type, as opposed to sprays, as they are easier to rub into the skin.

“Have a roll on for kids and sprays for around the face.”

What should you look for in a mosquito repellent?

With hundreds of mosquito-repelling products on the market, how do you know which to buy? 

Dr Webb advises to pay attention to the strength of the formulation.

“This refers to how long it lasts not how many mosquitoes it repels,” he clarifies. “The stronger the repellent, the longer it lasts. If you’re only going to be outside for an hour or two, you can probably choose a milder, less irritating repellent; even the lowest doses should provide a couple of hours' protection. We’re often too quick to reach for those high-strength products when we don’t need them.” 

While natural repellents can offer some protection against mosquito bites, Dr Ritchie advises caution when using them. 

“Some of the natural ingredients – tea tree, for example – don’t last that long, so you have to reapply frequently,” he says. “And sometimes people are making their own repellents at home using essential oils, so the chance of skin irritation is much greater.”

He says it’s also important to point out that some of the natural products are not safe for use on young children, while chemical repellents are safe for babies from three months of age onwards.

If you get bitten, what’s the best way to treat it?

If you do happen to get bitten by a mosquito, Prof. Ritchie says it’s important to resist the urge to scratch the itch. 

“If you don’t scratch it, it won’t be itchy,” he says. “The best way to soothe a bite is by using a topical antihistamine or anti-itching cream.