Does Eating Garlic Reduce Mosquito Bites?

Michael Greger M.D. FACLM · July 10, 2023 · Volume 62

4.7/5 - (46 votes)

Garlic is put to the test as a repellent for mosquitoes and ticks.

Discuss

Transcript

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

A few weeks ago, I released videos on DEET vs. natural repellents that we apply to our clothes or skin. But can the things we eat also have a repellent quality? No word yet on vampires, but we do have evidence on garlic and other blood suckers. Check it out.

Are some people just more attractive to mosquitos than others? Apparently so, as identical twins are most likely to be similarly tasty, compared to fraternal twins who only share 50 percent of their DNA––demonstrating an underlying genetic component that can be sniffed out by mosquitoes, although it’s not clear if it’s because some people smell better, or other people just smell worse.

We know pregnant women are twice as attractive to malaria mosquitoes, and also that mosquitoes are attracted to sweat. Human sweat contains components that are attractive to anthropophilic—meaning human-loving—mosquitoes. The unique composition of human sweat appears to explain its tantalizing effect, though sweat from some body parts is evidently more tantalizing than others. Skin emanations collected from armpits were less attractive compared to hands or feet. Here’s the graph. They think the difference may be caused by deodorant residues, since in a subsequent experiment, volunteers were asked to avoid using skincare products for five days, and after that, no differences were detected.

The creepiest bit of research I found was this. The parasites that cause the mosquito-borne disease malaria, which kills hundreds of thousands of people a year, makes you more attractive to, you guessed it, the mosquitoes that transmit malaria. What better way for the parasites to hitch from person to person. Instead of leaving it up to chance, some parasites manipulate their hosts in elaborate ways. I’ve talked about how the toxoplasma brain parasite draws mice to the smell of cat urine to get into cats’ brains. Or, how about the rabies virus concentrates in the saliva while tapping into the Cujo rage circuits> There’s even a parasite that needs to get from an ant to a bird; so, it turns the ant’s belly bright red to look like a ripe berry, and makes the ant stick it up into the air to confuse fruit-eating bird. Here’s the ants before and after infection. Just like malaria parasites making us particularly tasty to mosquitos.

Any way we can make ourselves less tasty? I’ve talked about the various mosquito repellents you can spray on your skin––both synthetic and natural mosquito repellents. But is there anything you can eat or drink to make you less of a target?

When you search the scientific literature for diet and mosquitoes, a lot of articles like this pop up, on diets for mosquitoes, like SkitoSnack for that artificial blood meal replacement. Feeding mice different diets makes a difference. But what about people?

One of the most common anecdotes is that vitamin B complex supplements protect against biting insects. Other anecdotal remedies include the taking of garlic, marmite, Vegemite, brewer’s yeast tablets, and alcohol. But you don’t know, until you put it to the test.

How about a randomized, double-blind, placebo-controlled trial of garlic as a mosquito repellant? A belief in the ability of garlic to repel insects seems to be widespread; so, researchers in Connecticut decided to see if it were true. They looked at the numbers of mosquitoes that did not feed on the subjects; the number of mosquito bites, the weights of the mosquitoes after feeding, and the amounts of blood ingested were all determined on people on and off garlic. And, the data did not provide evidence of significant mosquito repellence.

No surprise, given that even if you slather garlic oil on your skin, within 30 minutes mosquitoes don’t seem to care. Eating garlic may, however, help against ticks. Because military personnel can sometimes be at particularly high risk for tick bites and tick-borne diseases, the Swedish military conducted a randomized controlled double-blind trial of garlic to prevent tick bites among marines. Fifty swallowed the equivalent of about a clove a day of garlic, and fifty took placebo pills. Then, they all switched. And, there was a significant reduction in tick bites when consuming garlic compared with placebo–cutting the risk of tick bites by about 20 percent.

Twenty percent is better than nothing, but treating your clothing with something like permethrin has been shown to be 100 percent effective against deer ticks, the vector of Lyme disease. And so, that may be better than counting on garlic bread to save you.

Please consider volunteering to help out on the site.

Sources

Acknowledgements

Motion graphics by Avo Media

Topics

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

A few weeks ago, I released videos on DEET vs. natural repellents that we apply to our clothes or skin. But can the things we eat also have a repellent quality? No word yet on vampires, but we do have evidence on garlic and other blood suckers. Check it out.

Are some people just more attractive to mosquitos than others? Apparently so, as identical twins are most likely to be similarly tasty, compared to fraternal twins who only share 50 percent of their DNA––demonstrating an underlying genetic component that can be sniffed out by mosquitoes, although it’s not clear if it’s because some people smell better, or other people just smell worse.

We know pregnant women are twice as attractive to malaria mosquitoes, and also that mosquitoes are attracted to sweat. Human sweat contains components that are attractive to anthropophilic—meaning human-loving—mosquitoes. The unique composition of human sweat appears to explain its tantalizing effect, though sweat from some body parts is evidently more tantalizing than others. Skin emanations collected from armpits were less attractive compared to hands or feet. Here’s the graph. They think the difference may be caused by deodorant residues, since in a subsequent experiment, volunteers were asked to avoid using skincare products for five days, and after that, no differences were detected.

The creepiest bit of research I found was this. The parasites that cause the mosquito-borne disease malaria, which kills hundreds of thousands of people a year, makes you more attractive to, you guessed it, the mosquitoes that transmit malaria. What better way for the parasites to hitch from person to person. Instead of leaving it up to chance, some parasites manipulate their hosts in elaborate ways. I’ve talked about how the toxoplasma brain parasite draws mice to the smell of cat urine to get into cats’ brains. Or, how about the rabies virus concentrates in the saliva while tapping into the Cujo rage circuits> There’s even a parasite that needs to get from an ant to a bird; so, it turns the ant’s belly bright red to look like a ripe berry, and makes the ant stick it up into the air to confuse fruit-eating bird. Here’s the ants before and after infection. Just like malaria parasites making us particularly tasty to mosquitos.

Any way we can make ourselves less tasty? I’ve talked about the various mosquito repellents you can spray on your skin––both synthetic and natural mosquito repellents. But is there anything you can eat or drink to make you less of a target?

When you search the scientific literature for diet and mosquitoes, a lot of articles like this pop up, on diets for mosquitoes, like SkitoSnack for that artificial blood meal replacement. Feeding mice different diets makes a difference. But what about people?

One of the most common anecdotes is that vitamin B complex supplements protect against biting insects. Other anecdotal remedies include the taking of garlic, marmite, Vegemite, brewer’s yeast tablets, and alcohol. But you don’t know, until you put it to the test.

How about a randomized, double-blind, placebo-controlled trial of garlic as a mosquito repellant? A belief in the ability of garlic to repel insects seems to be widespread; so, researchers in Connecticut decided to see if it were true. They looked at the numbers of mosquitoes that did not feed on the subjects; the number of mosquito bites, the weights of the mosquitoes after feeding, and the amounts of blood ingested were all determined on people on and off garlic. And, the data did not provide evidence of significant mosquito repellence.

No surprise, given that even if you slather garlic oil on your skin, within 30 minutes mosquitoes don’t seem to care. Eating garlic may, however, help against ticks. Because military personnel can sometimes be at particularly high risk for tick bites and tick-borne diseases, the Swedish military conducted a randomized controlled double-blind trial of garlic to prevent tick bites among marines. Fifty swallowed the equivalent of about a clove a day of garlic, and fifty took placebo pills. Then, they all switched. And, there was a significant reduction in tick bites when consuming garlic compared with placebo–cutting the risk of tick bites by about 20 percent.

Twenty percent is better than nothing, but treating your clothing with something like permethrin has been shown to be 100 percent effective against deer ticks, the vector of Lyme disease. And so, that may be better than counting on garlic bread to save you.

Please consider volunteering to help out on the site.

Motion graphics by Avo Media

Doctor's Note

I previously covered repellents in my videos Is DEET the Best Mosquito Repellent? and Natural Alternatives to DEET Mosquito Repellent.

What about other natural repellents? The next video covers beer, bananas, and B vitamins.

The video I mentioned on toxoplasma is Toxoplasmosis: A Manipulative Foodborne Brain Parasite.

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