Review of DEET, picaridin and other ingredients in insect repellents


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Scientists are always looking for better ways to outsmart insects that leave itchiness in their wake. Despite the many tools studied, from tick-killing fungi to genetically modified mosquitoes, insect repellents remain “the first line of defense,” says Mustapha Debboun, medical entomologist and veterinarian. “It is an individual protection measure that any individual can take in hand.”

It is also important. In the United States, mosquito-borne West Nile virus is thought to have infected nearly 7 million people since it first emerged in New York in 1999, and nearly half a million people contract the disease each year. Lyme after a tick bite.

However, not all repellents provide the same protection, which is why Consumer Reports tests how well each repels real insects from biting real people. And it turns out that what matters most is not the brand or the type of repellent (spray, lotion or wipe) but the active ingredient and its concentration.

But what are these ingredients? And why do some products work better than others with the same active ingredients? Here are the answers to these questions and more.

What’s so great about DEET?

When it comes to active ingredients that can keep bugs away, it’s hard to beat DEET. It is “broad spectrum”, which means it works on a wide variety of insects, including mosquitoes, ticks and flies. When scientists test the effectiveness of new insect repellent ingredients, they compare them to DEET to see how they stack up.

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Although scientists long ago discovered that DEET works, they still don’t know why. DEET can mask the smell of humans, confuse the smell-detecting abilities of mosquitoes, or simply drive them away, perhaps because it looks like a naturally occurring substance they evolved to avoid. But it may be more than just a smell at work.

And it’s also possible that DEET is so effective against mosquitoes because it works on multiple levels, or even multiple levels at the same time, says Chris Potter, an associate professor of neuroscience at Johns Hopkins University School of Medicine who specializes in insect sense. smell.

Why DEET also repels ticks is even less understood, although the mechanisms are likely different from those of mosquitoes. One thing we know: ticks, which usually hitchhike when you come across them in brush or tall grass, are less likely to attach to your skin if they detect DEET, and they will avoid the patches on your skin where DEET is. That’s one reason it’s important to carefully apply repellent to all exposed skin when you want to avoid ticks, says Bryan Cassone, associate professor of biology at Brandon University in Manitoba.

DEET works, but is it safe?

DEET has been available to consumers for over 60 years, and people are estimated to use it millions of times each year. During all this time, scientists have found only a few cases of damage potentially related to it.

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A 1998 analysis by the Environmental Protection Agency investigating the health effects of DEET, for example, found that since 1960 the estimated incidence of seizures with a possible link to DEET exposure was 1 in 100. million users. A 2007 EPA Chemical Summary Report on DEET noted that many of these cases of adverse neurological effects were related to ingestion or “repeated dermal exposure or accidental ingestion of DEET that does not did not conform to the label instructions.

In other words, DEET can pose some risk if ingested or used improperly. Keep repellents out of reach of children.

And high concentrations are not necessary. The CR tests DEET repellents at concentrations up to 30%. More than that is simply not necessary to achieve long-lasting protection.

When you use a DEET-based repellent as directed, it poses little risk. The Centers for Disease Control and Prevention recommend it as a safe option for adults, children over 2 months old, and even pregnant women.

However, no chemical is without risk and DEET must be used correctly to be safe. According to the National Pesticide Information Center (NPIC), you should avoid applying DEET under your clothing (use it only on exposed skin and outside of clothing), wash it off your skin at the end of the day and try not to reapply. too often. Neglecting these tips could result in you receiving a higher dose of DEET than expected. Additionally, DEET can degrade some synthetic materials like plastic, so it should not be applied to certain types of clothing.

You may also be concerned about the long-term risks of DEET exposure. According to a 2008 NPIC fact sheet, “researchers have found no evidence that DEET causes cancer in animals or humans,” and there is no clear evidence of other long-term risks. of topical use despite the availability of DEET for decades.

What are OLE and picaridin?

OLE came to the attention of American scientists in the 1990s when they learned that a Chinese product called Quwenling repelled mosquitoes much better than other herbal products. One of its main components is the chemical p-menthane-3,8-diol, or PMD, which gives OLE its repellent character.

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The name “lemon eucalyptus oil” is somewhat of a misnomer. The Australian plant from which it comes, Corymbia citriodora (or lemon-scented gum), was once considered part of the genus Eucalyptus, but is no longer. And unlike lemon eucalyptus oil, OLE is not a true essential oil because it is refined and concentrated. In short, it’s not what it sounds like, although it is indeed a naturally occurring ingredient that is often effective.

Picaridin, also called icaridin, is a chemical that was developed by Bayer AG in the 1980s and 1990s. It is similar in structure to piperidine, a chemical naturally present in some pepper plants. It has been available to US consumers since 2005 and is especially popular as an insect repellent in Europe and Australia.

Are OLE and picaridin safe?

Compared to DEET, less is known about OLE and picaridin, but evidence suggests they are safe when used according to label.

OLE is classified as a biopesticide by the EPA, which means it is a naturally occurring substance considered to pose a lower risk than more conventional chemical pest control products. The main risk seems to be that it can be harmful if it comes into contact with your eyes. It should also not be used on children under 3 years old; its safety has not been well studied in young children.

Picaridin carries a small risk of skin irritation, but this appears to be rare. All of the possible long-term effects of these two ingredients have largely not been studied.

Why different performances?

Our testing cannot tell us why some repellents with the same labeled active ingredient last long while others do not. This is partly because, unlike cosmetics or other personal care products, manufacturers of EPA-registered repellents are not required to disclose all ingredients. Some of the non-active ingredients in a given repellent may affect its effectiveness.

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And manufacturers are reluctant to provide their formulas to researchers for testing — they consider them trade secrets — so independent scientific studies of insect repellents can’t test how a repellent’s non-active ingredients might contribute to its effectiveness. .

That’s why CR tests with the same products you buy on store shelves. So even if we don’t know all the ingredients of a product, we can see how well it works in comparison to other products on the market.

How are natural insect repellents?

The lower echelons of CR’s insect repellent ratings are mostly filled with “natural” insect repellents, meaning those whose active ingredients are essential oils. Lemongrass oil, cedarwood oil, citronella oil, and peppermint oil are some of the common ingredients.

It’s not that these ingredients don’t work. After all, they come from plants that have repelled insects “for millions of years,” says Joel Coats, distinguished professor emeritus of entomology and toxicology at Iowa State University. But there’s a problem: the molecules that make up many of these essential oils, called terpenes, are small and light. So while they’re effective repellents, Coats says, they evaporate quickly from the skin, which means they don’t last long, sometimes only an hour.

Additionally, the quality or potency of essential oils is highly variable and unpredictable, says Aaron Gross, assistant professor of toxicology and physiology in Virginia Tech’s Department of Entomology. And while essential oils may seem safer, some people may be hypersensitive or even allergic to them.

If you are interested in a naturally occurring repellent that should last longer, look for products with OLE.

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