Why do mosquitoes seem to love some people more? An expert explains

Mosquito season is in full swing, and it comes with plenty of advice about how to avoid getting bitten.

Some people swear by garlic or vitamin B. Others avoid bananas or light citronella candles before heading outside. But what does the science actually say?

London Morning host Andrew Brown spoke with Nusha Keyghobadi, a biology professor at Western University who studies mosquitoes, about why they bite, what attracts them and the best ways to keep them away.

The following has been edited for length and clarity.

Andrew Brown: Why is it that mosquitoes like people so much?

Nusha Keyghobadi: People are a really good source of food, especially for female mosquitoes, which are the ones that bite us. Females of some mosquito species need a blood meal to get the nutrients they need to develop their eggs, so we're a really good source of food.

AB: It often feels like there's one person who attracts mosquitoes more than everyone else. Why is that?

NK: Female mosquitoes looking for a meal use a variety of cues. Some of the biggest ones are body heat and carbon dioxide. Every breath you take releases carbon dioxide, and mosquitoes use that to find warm-blooded animals like us.

They also respond to chemicals your body produces — essentially your odour. Your smell is influenced by your genetics, your physiology and potentially what you've eaten recently. Those factors can make some people more attractive to mosquitoes than others.

AB: You mentioned what we eat. How much of that is actually in our control?

NK: That's a good question. There are a few studies that have looked at this. In the case of bananas, one study did find they made some people more attractive to mosquitoes.

But the effect wasn't very strong, and there was a lot of variation. Some people became more attractive after eating bananas, some became less attractive and for others it made no difference. So while there may be a statistical effect overall, it's hard to say whether avoiding bananas will make any difference for any individual.

AB: You also hear advice to eat more garlic. Is there anything we can eat that mosquitoes hate?

NK: Not that I know of. A few studies have looked at garlic and they didn't find a significant effect. Vitamin B has also been tested because there's a common belief that it reduces your attractiveness to mosquitoes, but I don't think there's good evidence for that either.

One food item that does have a little evidence behind it is beer. A few studies have shown that after drinking beer, people can become more attractive to biting mosquitoes.

AB: How about citronella candles and mosquito coils? What really works?

NK: The best protection is physical protection.

If you're trying to keep mosquitoes away from where you're sitting, a screened porch or a mesh shelter is probably the most effective option.

There are also products that use heat to vaporize a synthetic mosquito repellent, and those can be effective. But there isn't strong evidence that citronella candles are particularly effective.

AB: Do you use bug spray yourself?

NK: Oh, absolutely. When I'm doing field work, I definitely use insect repellent to keep mosquitoes from biting me.

AB: Before we go, remind us why mosquitoes are important. They do serve a purpose.

NK: Absolutely. I'd remind people that many mosquito species don't actually bite humans.

Mosquitoes are an important part of aquatic ecosystems because, from the egg stage through the pupal stage, they live in water, feeding on decomposing plant material and microbes. In turn, they provide food for larger aquatic invertebrates and fish.

Adult mosquitoes are also an important food source for dragonflies. They're an important part of the ecosystem, and some mosquito species are actually fascinating and do some really interesting things.