My friend recently gave me a little battery-powered device that’s supposed to keep mosquitoes away. He also mounted those little deer whistles on the front of his car, and placed ultrasonic mouse deterrents around his house. When I voiced my skepticism to all of the above, he said, “Anything’s worth a shot.”

That’s what makers of mosquito repellents are banking on, to the tune of $6.51 billion in 2022. And their market is projected to grow to $9.3 billion by 2029, partly due to the rise of mosquito-borne diseases — a byproduct of climate change.

So whose claims are actually backed by science? Here’s the red, puffy, itchy truth, according to the researchers and scientists who’ve studied them.

Is DEET Really Bad for You?

Probably not. It’s been around for more than half a century with fewer than 50 documented cases of serious toxic effects.

It’s also proven to be one of the most effective and longest-lasting repellents. The higher the percentage of DEET, the longer it will keep mosquitoes away, up to six hours.

“On average more than 200 million people use this repellent every year and it is certain that a lot of misery from nuisance biting and disease is overcome by this product,” says Bart Knols, Ph.D., a biologist and mosquito researcher with MalariaWorld.

But DEET can damage plastics, so be careful with it around accessories like watches, sunglasses and some synthetic fabrics.

What Other Synthetic Mosquito Repellents Work Well?

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Picaridin (aka icardin) and IR3535 appear to be as safe and effective as DEET when applied at the same dosage. Some studies suggest picaridin lasts longer, “all without the irritancy, odor and melted glasses that may accompany DEET usage,” says Michael Greger, M.D. and creator of nutritionfacts.org.

Consumer Reports named 20% picaridin products as the best overall insect repellent. At that percentage they should last up to six hours.

Does Citronella Work?

Barely.

Although citronella was the most widely used repellent before DEET, as a spray-on product it’s shown to last between 10 and 30 minutes.

“Despite inferior efficacy, I imagine it’s still so popular because it’s viewed as a natural alternative,” says Dr. Greger. “Citronella may be acceptable for brief exposure to nuisance mosquitoes, but it isn’t advised for protection if you really can’t afford to get bit.”

Citronella candles only decrease your chances of getting bitten by 20% to 40%. “The oil of citronella may give some protection, but most products only protect for up to an hour or so,” says Knols. “Candles with citronella hardly do anything, as do products like flowers and place mats impregnated with citronella oil.”

Is Natural Mosquito Repellent Effective?

Yes and no. Some are as effective as DEET, while others do virtually nothing. Here’s a rundown:

Lemon eucalyptus

Yes. Lemon eucalyptus (aka OLE, or the synthetic version PMD) is the only plant-based repellent recommended by the Centers for Disease Control and Prevention (CDC).

A product with 40% active ingredient is roughly as effective as DEET. It can repel aggressive species of mosquitoes for four to seven hours, and less aggressive ones for more than 12 hours. Note: It should not be used by pregnant women or children younger than three.

Other essential oils

Some. Clove oil can work for 90 minutes at a 10% concentration, according to Immo Hansen, Ph.D. and other researchers at New Mexico State University, who studied the effectiveness of 20 essential oils.

They also found 10% cinnamon oil works for 60 minutes, and 10% citronella for about 30 minutes. Other essential oils offer little to no protection.

“Based on our study, we recommend using repellents with the active ingredient DEET if you live in or are traveling to regions with a high risk of vector-borne disease transmission,” Hansen says. “However, plant-based repellents will work just fine to prevent nuisance mosquito bites in low-risk areas, as long as you reapply them as needed.”

Permethrin

Yes. Permethrin is not natural, but a synthetic form of pyrethrum derived from Chrysanthemums. It’s an insecticide used to kill mosquitoes, flies, ticks, fleas and cockroaches. When applied to clothes, it can last up to two weeks and through multiple washings.

According to the National Institutes of Health, it appears to be effective and safe.

Garlic and other foods

No. Research has shown eating garlic does not keep mosquitoes away. So far, no other foods, including beer, gin and tonics, bananas and B vitamins, have been proven effective at preventing mosquito bites.

Spatial repellent devices

Yes, but usually not as well as spray-on products.

Spatial repellent devices like Thermacell or Off! Clip-On disburse repellent (metofluthrin, linalool or d-cisltrans allethrin) through fans and/or heat into a radius around your person or your work/hangout space. They’re not natural but sometimes perceived as such.

These are proven to work on mosquitoes and ticks, although results vary depending on mosquito species and, in some instances, how windy it is.

Mosquito-repelling wristbands

No. Despite being widely popular, there is no scientific evidence that bracelets with citronella, DEET or other essential oils repel mosquitoes. “DEET-impregnated wristbands repel mosquitoes only from the sliver of skin covered by the band,” says Dr. Greger.

Adds Knols: “These simply do not work and are misleading users. Worse, people use such bracelets when they visit the tropics in order to protect themselves against malaria because they do not want to take anti-malaria medication (prophylaxis). This, therefore, is grossly unethical.

“Companies that manufacture such products know that they don’t work yet are still allowed to sell such products. This should be forbidden by law. The same applies to stickers with repellent in them, or patches that can be attached to clothing. Basically anything that is a point source and not covering all exposed skin is not giving decent protection.”

Electronic repellents and other gadgets

No.

“Ten studies were done on them, and all ten found that there was no difference in the number of mosquitoes landing on people with or without the gizmos, and experiments out in the field confirm they have no effect on preventing mosquito bites,” says Dr. Greger.

Adds Knols: “This is another example of a massive market for which there is not a shred of evidence that they work.”

According to Hansen’s research, light-based repellents like colored lightbulbs don’t work either on mosquitoes, although they can work on moths and beetles.

Knols also doesn’t recommend coils that burn to create smoke outdoors, as well as indoor electronic vaporizers. Neither are proven particularly effective, and both can contain chemicals that are harmful when inhaled.