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Mosquito myths busted

August 20, 2021

This World Mosquito Day, check out what really protects you against them, why they are good for the environment, and the truth about the sweet blood theory.

An anopheles mosquito on a human body
Summertime and the livin' is easy for mozzies — much to the chagrin of our author Carla BleikerImage: Soumyabrata Roy/NurPhoto/picture alliance

Summer could be so nice right now. Finally, a chance to meet friends outside, where there's less to worry about in terms of corona. It could be a barbeque party in a garden, cocktails on a terrasse, out at your favorite bar or an afternoon swimming at a lake. If it wasn't for the perpetual buzzing of those little blighters, that is.

Count yourself lucky if you've no idea what I'm talking about. I've heard of these people who somehow manage to get through the warmer months with just one or two mosquito bites. I am most definitely not one of them.

The past two summers in Washington D.C. were especially bad. Once, after just a short walk, I had 30 mozzie bites on my legs. I counted myself lucky that mosquitos don't always carry dangerous diseases — at least not in the more temperate regions. But it still wasn't a nice experience.

It's said there are people who have "sweet blood" that attracts mosquitos. But is that true? Does coffee protect you against them? Does it help to smear toothpaste on the bites? And why can't we just eradicate the whole world of the rotters once and for all?

My apologies to all the animal rights advocates and environmentalists. But when you have to wake every two hours to pour ice cold water over your legs, such murderous thoughts come easy. 

If there is any truth in that sweet blood theory, or the coffee and toothpaste, Helge Kampen can probably help. Kampen heads a laboratory at the Friedrich Loeffler Institute (FLI), Germany's National Institute for Animal Health. And he specializes in "blood sucking Articulata animals, basically insects and ticks." So, if anyone can, Kampen should be able to help us bust the toughest mosquito myths.

Helge Kampen working at a microscope, studying mosquitos
Kampen studies blood sucking animals in his laboratory on the Island of Riems off northeastern GermanyImage: Stefan Sauer/dpa/picture alliance

Turn off the light!

Everyone knows this one: If you've got a window open in summer, you've got to turn the lights off or the mozzies will fly right in. Right? Or wrong?

"My mom used to say that as well when I was a kid," says Kampen. But it's not true.

You might get other insects in the room if you leave a window open after sundown in summer, but it will be things like moths. Moths are attracted to light.

But mosquitos are not attracted by the light. They like the air you exhale, perspiration and your bodily odor. And those are different from person to person, which brings us neatly to our next point.

Why mosquitos prefer some people more than others

"That idea about the sweet blood is not quite right," says Kampen. Mosquitos don't care whether you eat lots of candy or not.

Well, I'm relieved to hear that I won't have to reduce the amount of chocolate I eat. But I still don't understand why I get seven new mozzie bites after grabbing some lunch outside and my companion gets none.

"Each of us perspires differently and our odors differ, too, and that makes us attractive to different types of mosquitos," says Kampen.

The exact type depends on where you are. So, if you move to a new town or go on holiday somewhere, you may have more or less of a problem with mosquitos.

There is one nutritional factor that can play a role, however, and that's alcohol.

"Alcohol attracts mosquitos," Kampen says. "You give off different odors when you drink alcohol, and that happens via the skin, so that makes your skin more attractive after you've had alcohol."

Smokers, meanwhile, are less of a popular "landing site." As a non-smoker who likes to drink with friends once in a while, I find that totally unjust. But what's just in life, hey? Case in point: "Mosquitos are attracted to women at particular stages in their menstruation," says Kampen. Well, isn't that just wonderful?! 

Mozzie spray, coffee — what helps?

If you use an anti-insect spray to protect yourself against mosquitos, Kampen recommends those containing the repellent icaridin (also known as picaridin). "They are the best," he says.

Icaridin is active against a broad spectrum of insects and it's even recommended by the World Health Organization as a prevention method for malaria.

Aside from sprays, you should try to cover as many potential mozzie landing sites as you can — wear long sleeves and trousers. That's obviously not a lot of fun in summer. 

So, here's another tip: "Don't leave standing water where mosquitos can breed!"

If you've got a garden and any water containers, like rain barrels, buckets or old tires, lying about, make sure you cover them up. And make sure you empty them every seven to 10 days. Mosquitos lay their larvae in standing water and it takes about two weeks in temperatures of around 20 degrees Celsius (68 degrees Fahrenheit) for them to fully develop into adult mozzies.   

But there's not much that the expert can tell us about other "natural" protection methods. For instance, it's supposed to help if you burn coffee or eat garlic (so that's the same as with vampires, right?).

Kampen has heard of those ideas, but says there's no evidence to prove them. "There are very few standardized trials in that direction," he says.

Mosquitos on the surface of some water outdoors
Mosquitos like it when it's wet, so cover up any open, flat containers that can hold water in your gardenImage: Mortuza Rashed/DW

Pour some schnapps on it. Really?!

And what helps if you've been bitten? Why does it hurt so much?

"Your body reacts the way it does because mosquitos inject saliva into the wound to help them suck up blood," explains Kampen. "That saliva contains a lot of bioactive molecules — it's a real cocktail. And we all react differently to it."

Well, congratulations to all of you for whom mosquito bites don't swell up to the size of a dinner plate, making sleep in summer a nightmare.

The one thing that's the same for all of us is that "our bodies produce histamine and that causes the wound to itch."

So, antihistamine creams can work against the pain. But your own spit and toothpaste can help as well. That's because all three of them have a cooling effect. And cooling is good.

You can even pour cold schnapps on a mozzie bite, says Kampen, and it disinfects at the same time.

But don't drink it because that will just make you even more attractive to those blasted biters!

"Also, be brave and try not to scratch the spot for at least two days," says Kampen, "otherwise you risk a secondary infection through bacteria."

Mosquito bites on a human body
As hard as it is, don't scratch it or it will get worseImage: picture-alliance/dpa Themendienst/K. Kraemer

"Nature is free"

"Journalists often ask me, "What use are mosquitos?'" says Kampen. "And my only response is 'What use are you?'"

It a fair point. "It's just nature, and nature is free of reason. There's no meaning or purpose of living things." We all just exist.

But the biologist does then say that mosquitos perform a particular function in our ecosystem. They play an important role in the so-called food web. Mosquito larvae are food for fish, amphibians and other water insects. And the adults are food for birds, bats and again other insects. So, if we eradicated mosquitos, all those other animals would have a huge problem.

Oh well. I guess those of us who smell especially good will just have to grin and bear 30 bites a night… for the good of everyone.

Carla Bleiker
Carla Bleiker Editor, channel manager and reporter focusing on US politics and science@cbleiker