After putting in more than 30 hours of research, reading ginormous stacks of scientific papers on safety and efficacy, and coating ourselves with 10 bug repellents, we think that Cutter Backwoods Dry with 25 percent DEET is the one you should get. Out of all the sprays we tested, it was the easiest to apply and the most pleasant to wear, and it offered the most reliable sprayer. Cutter Backwoods Dry can repel disease-carrying mosquitoes (and to a lesser degree, ticks) for about three to four hours without your having to put more on. If you’re worried about DEET, don’t be—it’s the safest repellent for the most people, from kids as young as 2 months old to pregnant women. And even though DEET hasn’t been tested on pregnant women in their first trimester, experts suggest that all pregnant women use insect repellents that contain DEET, since the danger of Zika to an unborn baby is higher than any potential danger from DEET.
If you can’t find the Cutter repellent, reach for Coleman High & Dry with 25 percent DEET instead. We actually liked the Coleman formula a tiny bit more to wear, as it felt slightly lighter than the Cutter spray. But people have complained, both to us and in online reviews, that the nozzle on the Coleman can is prone to both breaking and clogging, leaving them with a full can of bug repellent and no way to get it out. Fail. But it’s a great spray otherwise, and it has the same amount of DEET as our top pick, so it will provide the same amount of protection.
For this guide, I talked to Dr. Mark Fradin, a dermatologist who co-authored one of the seminal papers on the efficacy of mosquito repellents, and Thomas Mather, the director of the University of Rhode Island’s Center for Vector-Borne Disease and its TickEncounter Resource Center, known in some circles as “The TickGuy.” (I wonder if that’s on his business cards.)
I’m also a science writer with a PhD in chemistry, which means I’m used to combing through scientific literature and then interpreting and making sense of it. I also don’t inherently mistrust a compound just because it has a long, complicated-sounding name. (I don’t inherently trust it, either. I’m chemical-name neutral.)
Probably the number one reason people wear bug repellent is for comfort, said dermatologist and bug repellent efficacy expert Dr. Mark Fradin. And yes, we tend to reach for that spray can when it gets “all bitey outside” (as my 3-year-old puts it). But increasingly, people are slapping on the bug spray for another reason: disease avoidance.
A few diseases are making the rounds. Although no one in this country gets fever ’n’ ague (aka malaria) like Laura Ingalls anymore, some new diseases have moved in, namely a few types of encephalitis, possibly chikungunya, and of course West Nile virus. But contrary to what TV news reports would lead you to believe, these diseases are not common. “The risk of getting West Nile is not terribly high,” Fradin told me, exhibiting a flair for understatement. According to the Centers for Disease Control and Prevention, the United States saw a total of 2,469 cases of West Nile virus in 2013, and 119 people died from it that year (PDF). This is a vanishingly small percentage of the 317,292,487 people who lived in the US in 2013. And only 1 percent of people who get West Nile actually develop severe symptoms. Still, that doesn’t mean anybody wants the disease, or any other that mosquitoes carry, so on goes the bug spray. (Want to know if West Nile is in your area? Check out this nifty map.)
Not wanting to be left out of the fun, ticks carry a variety of diseases too. The best known of these is probably Lyme disease, which at around 20,000 to 30,000 confirmed cases in 2013 is the most common insect-borne illness in the US. This one likes to hang out on the East Coast and the upper Midwest, though, so the risk depends a lot on where you are. While Lyme disease won’t kill you, for some people it can be debilitating and last for years. It isn’t a nice disease to get. Unfortunately, no bug repellent is 100 percent effective against ticks. If you really want to guard against their diseases, you’ll need permethrin. (You can read more about this topic in the section about ticks.)
Things you want in a bug repellent: It has to repel bugs, be safe to use, not feel gross on your skin, and not be crazy expensive. Also, the smell should not make you gag.
Let’s address the first thing first, and talk about efficacy. Fortunately, a lot of scientific research on bug repellents exists. After reading gigantic stacks of papers and articles, we found that they all point to one repellent that’s tops in both safety and efficacy: DEET. Hands down, DEET is the safest and best-working bug repellent out there.
We’ve had many people ask us why we didn’t test any products with picaridin, a bug spray with a non-DEET active ingredient. We have much more below on picaridin (and other non-DEET repellents), but in short, picaridin is a newer bug repellent that hasn’t been in use as long as DEET has, so we don’t have nearly as much safety data on it. We’re not saying that picaridin isn’t safe—the data we have says that it is. But we’ve seen far fewer safety studies done on picaridin than on DEET.
At one time, doctors thought a link might exist between seizures and DEET use in kids, but later they found that not to be true. Some people are also nervous about DEET because in high concentrations it can melt plastic. This is true—100 percent DEET can damage both leather and plastic materials. But we are not advocating using high concentrations of DEET. The max you should use is about 30 percent, tops. Our pick has 25 percent DEET, and we tested it on a bunch of different materials and fabrics, and saw no damage.
But here’s a very important point: The percentage of DEET in a bug repellent determines how long it will last, not how well it wards off bugs. So the higher the percentage, the longer it works. We think the best formula for most folks contains about 25 percent DEET. According to some of this research we mentioned, this amount should give you about three to four hours of protection without your having to reapply, plenty of time for a summer picnic or an afternoon hiking trip. If you need longer protection than that, reapply rather than going with a higher concentration of DEET.
You could get by on a lower percentage of DEET. Many of the main offerings from brands such as Cutter and Off have a 15 percent concentration, and several sprays out there have only 5 to 7 percent. But according to the CDC, you should choose a repellent with at least 20 percent to ward off ticks, as well. And since ticks can cause Lyme disease and other nasties, we think it’s important to protect against them. Our pick, and most of the ones we tested, have 25 percent DEET.
We looked for sprays with only 20 percent, but few are available in stores. The ones we did find were lotions, which we think aren’t great—you can’t apply lotions to your clothes, and mosquitoes can bite through some fabrics. So we skipped testing any repellents not in spray form, which includes wipes too. We also nixed products that combine bug spray and sunscreen. Because sunscreen needs applying more often than insect repellent, using a combo type would pile on more bug stuff than you need. In addition, according to the CDC, using a combination type may ding the effectiveness of the SPF. The CDC suggests putting on the sunscreen first and then applying the repellent. Also, you may have to reapply the sunscreen more often, due to the lowered-SPF thing.
So once we applied all the above criteria to what sprays we would test, we didn’t have that many left. We did look at other people’s rankings of bug sprays, but we couldn’t glean much useful information. Consumer Reports ranked a spray with picaridin, a repellent that doesn’t work as well as DEET (more here), as number one; the testing house was all over the board with the rest of its recommendations, though it didn’t evaluate any of the dry formulas. (Consumer Reports even included some herbal ones, which the science says don’t do much.) Recently NPR reported on a paper that ranked some bug repellents, but those researchers looked at efficacy only, nothing else. In 2014, Vogue published an article with some good information, but that piece gives neither reason nor ranking to its recommended-repellent list. Consumer Search has some recs, but they’re based on CR’s picks; they also include herbal sprays, which don’t work. We also found several sites, in the wake of Zika, that list a bunch of sprays but don’t test or rank any.
In the end we rounded up the Consumer Reports picks, as well as best sellers from Amazon and Drugstore.com that met our criteria. These were:
I tested these products for skin feel and scent. Because strong concentrations of DEET can dissolve plastic, I tested the sprays to see if they damaged plastic bags and three kinds of common clothing fabric. The good news is that except for some slight staining, none of them damaged the plastic or the fabrics. The bad news is that all but one of the above sprays felt oily on the skin and just … gross. Like, “No way am I going to want to wear this” gross.
The only one that didn’t make my skin want to gag was a “dry” formula, the Off Deep Woods Insect Repellent VIII. After I sprayed this one on my arm, it dried in less than one minute, and I couldn’t feel that it was still there. Running my hand over the spot I sprayed, I could detect only a slight oiliness.
To compare apples to apples, we then went back and found three more “dry” repellents:
Honestly? Any of the four dry brands we tested are good, and we didn’t see a lot of difference between them. None of them damaged the fabrics I tested them on. All of them were only slightly oily to the touch (and feel) on my skin. They smelled more or less the same, which was not very much at all. And judging from their ingredient lists, they all have basically the same things in them (see more about this topic in What else is in bug repellent).
Here’s what we didn’t do: test how well each bug spray worked at repelling insects. That takes a special lab setup, or field testing in mosquito-heavy areas. And even when you have the resources to do that kind of testing, the University of Rhode Island’s Thomas Mather said, getting it exactly right is kind of tricky. So we decided to presume that the efficacy of each of these repellents is based solely on the percentage of DEET they contain and nothing else. (Which it should be, ideally.)
But even after we say that these repellents all work about the same, we have to note that other things set them apart. DEET is an oil, and so it can feel, well, oily on the skin. Therefore, I tested how yicky or non-yicky each repellent felt on the underside of my arm upon application, after 10 minutes and after 20 minutes. I also noted whether the repellent had a strong odor, whether it puddled on the skin, and how easily I could get a light, even spray. Bonus points if the repellent had a locking cap, which keeps the spray from going off in a bag.
Aside from the oily feel, one of the top complaints about DEET is that it melts materials, usually plastic. The back labels on cans of repellent kind of warn against this, saying that the substance might damage materials such as rayon, acetate, spandex, furniture, watch crystals, leather, or painted surfaces. No watch crystals or fancy purses were harmed in the making of this guide, but I did smear the repellents on three types of fabric: 100 percent cotton, a 95 percent rayon and 5 percent spandex blend, and a 80 percent polyester and 20 percent spandex blend. I also tried it on plastic sandwich bags. But oh, happy day! This concentration of DEET did not damage any of the materials. The fabrics had some slight oil staining from the DEET, which was pretty much universal across all the sprays I tested. To my eyes, though, they didn’t suffer any detectable damage other than that. And the sandwich bags came out completely unscathed.
Of all the bug repellents we tested, the dry versions were by far the best. And of those, Cutter Backwoods Dry was the best all around to use. It felt less oily both 10 and 20 minutes after application than most of the other sprays. It has a locking cap, which means that you can throw the container into your bag without having to worry that it will spray repellent everywhere. The price, usually less than eight bucks, is roughly the same as that of the other dry repellents out there.
In our tests it went on just a touch heavier than the runner-up, Coleman High & Dry, and it tended to puddle a tiny amount more on the skin. It was also the smallest bit stinkier than the Coleman product, but the smell dissipated quickly, with only a slight reminiscence of summer camp 20 minutes after I put it on. It was barely noticeable on my skin, and it felt only the tiniest bit greasy when I rubbed my hand across it, less greasy than the other repellents I put on.
Cutter Backwoods Dry contains 25 percent DEET, which is the safest (really) and most effective insect repellent you can buy. This formula will give you happy relief from nasties such as mosquitos and ticks for about three to four hours, long enough for an afternoon barbecue or a hike in the woods, without your having to reapply. It’s also quite easy to find in a big-box store, so getting your mitts on some should be a snap.
Just like the other 25 percent DEET repellents we tested, Cutter Backwoods Dry does not damage either plastics or fabrics.
Even though DEET has been tested out the wazoo and found to be very safe, it has its drawbacks. One is that you have to wash it off after use. This step is to minimize your potential exposure to it, since the longer you leave it on your skin, the better the chance that you’ll absorb it. Although DEET has a reputation as being a scary chemical, not much evidence shows that it actually is harmful. Regardless, scientists believe that if it does have any damaging effects, such as a chance to cause neural disorders, they may come from large and repeated exposures over time. It is a pain to have to jump into the shower following an afternoon of fun in the woods, but you’re probably all gross and sweaty at that point anyway.
A related flaw is that DEET tends to have an odor that some people don’t like. Our pick does have a very light bug-spray scent—but we found that it fades away after 20 minutes.
Another strike against DEET is that it can damage some kinds of materials, such as plastics, fabrics, and fiberglass. Make sure to wash your hands after applying, and don’t spray it around tents and your fancy kayak. Complaints of damage tend to accompany sprays with very high concentrations of DEET. Our pick, Cutter Backwoods Dry, didn’t damage any of the materials we tested it on, nor did any of the other sprays we tried.
In the unlikely event that you can’t find Cutter Backwoods Dry in the store, go for Coleman High & Dry with 25 percent DEET. This product was our former top pick, but people were complaining that the nozzle easily clogged or even broke, leaving them with a half-full can and no way to get the spray out. Not cool. We reached out repeatedly to the company about this issue and got no response. Other than that, Coleman High & Dry is a great bug spray—it goes on ever so slightly drier and more evenly than our top pick. But if you don’t want to risk buying a can and being unable to use it all, go for the Cutter spray. The difference in application is really small.
One odd thing about the Coleman High & Dry: It left a pasty residue on our test fabrics, a result of the cornstarch that makes it a dry formula. When I sprayed the repellent on my arm, however, I didn’t see or feel any film at all. I should note that I smeared quite a bit on the fabric with a cotton swab when I tested; nowhere near that amount should get in one place on your clothes or skin, unless you’re doing it wrong.
To start, all products marketed as on-skin bug repellents have to be registered with the Environmental Protection Agency. Of those, only some are actually effective at keeping bugs at bay. According to scientific research and the Environmental Working Group’s well-researched and surprisingly sensible Guide to Bug Repellents, four insect repellents work pretty well. They are DEET, picaridin, the creatively named IR3535, and oil of lemon eucalyptus.
Of those, DEET works the best. And it’s the only one you’ve probably heard of. DEET is the safest bug repellent out there, according to both the CDC (PDF) and the EPA. It’s also one of the few okayed for use on babies as young as 2 months and pregnant women in their second and third trimesters. DEET, aka N,N-diethyl-m-toluamide, was developed by the US military. It’s been around the longest, about 50 years, and it’s been the most tested, both for efficacy and safety. You can read more on that in “DEET Is Actually Quite Safe—Really.”
With DEET, you might think that the higher the concentration, the better it keeps mosquitoes away. Actually, according to a 2002 paper in The New England Journal of Medicine, the higher the concentration of DEET, the longer the protection time. Led by the dermatologist I talked to, Dr. Mark Fradin, the researchers behind this paper found that complete protection from mosquitoes lasted from one to two hours for repellents with 5 to 10 percent DEET and around four hours for those with 20 percent DEET. Repellents with up to 50 percent DEET kept skeeters away only a little longer than that, and the length of protection leveled off completely at 50 percent DEET. That means you can totally skip bottles of 100 percent DEET, even for deep-woods hiking trips (and this is the stuff that might melt your gear anyway).
In fact, the best idea is to match the DEET percentage with how long you’re going to be outside. Only an hour or so? Go with the 5 to 7 percent DEET repellents that are pretty commonly available. Want your protection to last all day? Go with a spray that has a higher percentage of DEET. It’s probably better to reapply, though; bug spray can wash off during sweating or swimming, Fradin said. That’s why we picked a spray that has 25 percent DEET. This amount hits the longer-protection sweet spot and also can help keep ticks away. If you need it on for a longer time, just freshen up that spray.
You have another option, however. A few bug sprays and lotions have DEET embedded in a matrix so that it releases gradually and gives all-day protection. 3M’s Ultrathon Insect Repellent Lotion is one of these. Sawyer also makes a timed-release 20 percent DEET lotion. We didn’t test either of those products, though, since they aren’t sprays; lotions aren’t easy to put on your clothes, so they aren’t the best pick for most people.
Picaridin, aka Icaridin, Bayrepel, Saltidin, or hydroxyethyl isobutyl piperidine carboxylate, is a synthetic bug repellent that Bayer created in the 1980s. Sawyer is one brand that uses picaridin, but Avon sells some repellents with it, too. Picaridin is supposedly as effective as DEET and not as liable to damage plastics and the like. However, it hasn’t been safety-tested nearly as intensively as DEET has. Through more than 60 years of studies, scientists have found that DEET is safe for everyday use and very effective at keeping multiple types of mosquitoes at bay. That kind of data just doesn’t exist for picaridin. We’re not saying that picaridin isn’t safe. According to the data we do have, it’s fine, basically causing only skin irritation in some people, and even that effect is uncommon. But researchers have done far fewer studies on picaridin than on DEET. It’s kind of like getting somebody you’ve known your whole life, versus the guy down the street that you’ve known for two months, to babysit your kids. The new guy might be fantastic—but you know so much more about the first guy that it just seems wiser to go with him.
IR3535’s real name is 3-[n-butyl-n-acetyl]-aminopropionic acid, ethyl ester, and it was made to mimic a naturally occurring amino acid. Unfortunately, studies have shown that it isn’t as effective as DEET, and researchers haven’t examined it for safety as closely. Both Coleman and Avon have repellents with IR3535. (Remember, though: Don’t combine sunblock and bug spray.)
Oil of lemon eucalyptus sounds all natural and happy, doesn’t it? Too bad it’s the worst of the lot. Extracted from eucalyptus trees, the compound para-menthane-3,8-diol is called PMD when it’s made in a lab. This repellent does not work as well as DEET. Repel, which sells the stuff, goes so far as to suggest that you not use it in areas where West Nile virus is high. You’re not supposed to put it on kids younger than 3 years old, according to the CDC. It also isn’t the same as “pure” oil of lemon eucalyptus, the essential oil. The CDC does not recommend using this as a repellent, since it hasn’t been tested for either safety or efficacy. And it isn’t registered with the EPA as an insect repellent.
As for other natural repellents that some people seem to like so much—repellents containing ingredients such as citronella, cedar oil, geranium oil, peppermint and peppermint oil, and soybean oil—those aren’t registered with the EPA, meaning that companies selling them don’t have to test them for efficacy. And that’s good news for such companies, since such “natural” repellents tend not to work very well, giving protection against mosquitos for less than 20 minutes on average. Even at the time you put them on, some barely work better than having no repellent at all.
Bug-repellent wristbands don’t work, either. Consumer Reports tested them and suggests you skip them. And according to this Huffington Post article, devices that try to repel mosquitoes electronically, including apps, don’t work either; the writer quotes this study, which says that some devices actually increased the number of mosquitoes biting. The American Academy of Pediatrics echoes this advice and adds garlic or vitamin B1 pills, birdhouses or bat houses, and bug zappers to the list of things that don’t work.
So it looks like if you want to keep the biting bugs away, bug spray it is. And DEET is the best candidate.
A word to the wise about efficacy testing of bug repellents, though. As the CDC says, “repellent efficacy and duration of protection vary considerably among products and among mosquito species.” The agency goes on to say that the protection is “affected by ambient temperature, level of activity, amount of perspiration, exposure to water, abrasive removal, and other factors.” Basically, the conditions in which the bug spray was tested may be different from the environment you’re using it in. Some companies test repellents by having volunteers stick their arms inside a mosquito-infested box. Some test products in, say, Cambodia. And what works in those situations, against those types of mosquitoes, could be better or worse in your local park, against the breeds of mosquitoes that live near you. In addition, a person’s body chemistry affects how well a repellent works. “People may experience some variation in protection from different products,” notes the CDC. And dermatologist Dr. Mark Fradin agrees: “It’s very dependent on the individual,” he told me, and some people are just more attractive to mosquitoes than others. “What may be great for one person might not be good for their friend.”
If you haven’t heard of Zika, it’s a disease that you can get primarily from the bite of an infected mosquito, and it can cause birth defects in unborn babies. Although the disease has been around since 1947, it has blown up recently in the Americas. For most people, getting Zika isn’t a huge deal—sometimes you’ll have a fever, a rash, joint pain, or red eyes for a few days to a week, but other times you won’t exhibit any symptoms at all. For pregnant women, however, it can be scary. We know now that if a pregnant woman contracts the Zika virus, it can cause microcephaly, a birth defect in which the unborn baby has a small head and a potentially damaged brain. Several newer studies on mice show that the Zika virus is a direct cause of brain damage in a developing fetus, and newborn mice pups show signs of microcephaly.
As of the end of April 2016, people have gotten Zika in Mexico, the Caribbean (including the US Virgin Islands), Central America, some Pacific islands (including American Samoa but not Hawaii), South America, and Cape Verde. Reports indicate no instances of people in the continental US contracting Zika locally, but right now health officials in 42 states have reported people with Zika, all acquired in other countries. As of April 13, 2016, the CDC says that the US has seen 358 cases of Zika.
When it comes to pregnant women and Zika, researchers still face a lot of unknowns. The CDC says that the virus can cause more problems besides microcephaly in fetuses, including other brain defects, eye defects, hearing loss, and growth impairment. At this point, nobody knows yet how likely a pregnant woman is to pass the virus to her unborn baby, or how likely that baby is to get a birth defect from Zika.
Hospitalization or death from Zika is very rare. Zika can also lead to Guillain-Barré syndrome, in which a person’s immune system turns traitor and attacks nerve cells. The CDC says that it doesn’t know the link between Zika and Guillain-Barré, and that other infections aside from Zika can set the syndrome off too. On top of that, the agency doesn’t say how likely Zika-triggered Guillain-Barré is, just that it happens in “a small number of cases.” The CDC estimates that in a year, about 0.001 to 0.002 percent of the US population will get Guillain-Barré from any infection. Of those, about one in 20 die from it.
The most likely way you can get Zika is if a mosquito that has the virus bites you. Two types of mosquitoes that can carry Zika are Aedes aegypti and Aedes albopictus. Both kinds of mosquitos are in the continental US, though they seem to hang out mainly in the South, Midwest, East, and Southwest. These mosquitoes can also carry dengue, chikungunya, and yellow fever, so they’re really fun species to have around.
The absolute best way to avoid contracting a mosquito-borne illness, Zika or not, is to avoid being bitten in the first place. We’re standing by our recommendation of using a bug repellent with DEET. Such products are the most effective, according to older research and to a study published earlier this year specifically on the two types of Zika-carrying mosquitoes. DEET is the repellent with the most safety information available, and the data says that it’s safe for infants 2 months and older as well as for pregnant women past their first trimester. And even though it hasn’t been tested on pregnant women in their first trimester, experts suggest that all pregnant women use DEET-containing insect repellents, since the risk from Zika to an unborn baby is higher than any risk from DEET.
But Zika can be sexually transmitted, too, from infected men through their semen, both anally and vaginally (and maybe through oral sex). The best way to avoid getting Zika from an infected man is to not have sex with him or to use a condom. Latex condoms are the best for this purpose, and we have a recommendation if you need to go there. Zika has the potential to transmit through blood transfusions, as well, although researchers have very little information on that possibility right now; the CDC acknowledges “multiple reports” but little else.
DEET isn’t 100 percent effective against ticks. For better tick protection, treat your clothes (and especially your shoes) with permethrin. We did not test any permethrin sprays, but here’s one that gets great reviews.
As I mentioned above, if you’re going to get a insect-borne illness in this country, you’re statistically most likely to get Lyme disease. It’s carried by black-legged ticks, aka deer ticks, and most prevalent on the East Coast and in the Midwest. Ticks can carry some other scary diseases, too, 15 by the CDC’s last count, and some ticks can carry more than one of them! It’s just a party waiting to happen.
Besides being gross, ticks are sneaky. Once one crawls on you, it can take hours before it bites. But the good news (yes, there is some) is that it takes about 12 hours after a tick attaches to start transmitting disease (except for deer tick disease, which took only 15 minutes in a study on mice, yikes). So in general, if you can get the tick off before it bites, or soon after, that’s good. But it’s obviously better if you can keep ticks off your person entirely.
The TickEncounter Resource Center suggests treating your clothes, especially shoes and socks, with permethrin. This substance is an insecticide; it not only repels insects but also kills them. It’s safe only for clothing, though, so don’t spray it on your skin. You can buy permethrin-treated clothing, purchase a spray bottle of the repellent itself (again, we didn’t test this one), or have your clothes treated by a company to be bug-proof (PDF order form). It doesn’t last forever—about six washes if you do the application yourself, and up to 70 for the professionally treated stuff. But it’s far and away the best way to keep ticks from biting you, said Thomas Mather, director of the University of Rhode Island’s Center for Vector-Borne Disease, aka The TickGuy. It works against all kinds of ticks, regardless of species. Mather mentioned that lone star ticks, the ones that carry Rocky Mountain spotted fever, are a little harder to kill. “They will fall off, but they don’t always die. The deer ticks were uniquely susceptible,” he said.
Permethrin-treated clothes work pretty well to keep ticks from biting you, according to this research. But think about skipping the expensive shirts. If you treat just your shoes and socks, you’re 76 times less likely to be bitten by a tick than if you’re wearing untreated footwear, which is a pretty big deal. In the study, people wearing treated shirts and shorts were only about four and two times less likely, respectively, to be bitten, so those pieces of treated clothing may not be worth the dollars. Ticks tend to crawl up on you from the ground, which is why your footwear matters more.
Some evidence indicates that DEET can repel ticks, though it isn’t perfect. According to the Connecticut Department of Agriculture (PDF), “concentrations of DEET that might prevent tick attachment may not deter a tick from walking across the skin to unexposed and untreated areas.” And not a whole lot of research has looked into what kind of repellent can keep away I. scapularis, aka deer ticks, the ones that carry Lyme disease. A 20 percent DEET repellent is about 86 to 87 percent effective in keeping ticks off either clothes or skin, according to some older research. Some very recent research says that a 20 percent DEET repellent is enough to keep deer ticks off for four to four and a half hours.
However, DEET is not 100 percent effective against ticks, Mather told me. It won’t hurt to wear a repellent with DEET against ticks, “but what I worry about is people depending on it, and they may be disappointed in the level of protection,” Mather said.
Regardless, a repellent with 20 percent DEET (or 25 percent, like our top pick) can give you relief from mosquitoes and possibly some protection from ticks for several hours. But for super-duper protection against ticks, go with the permethrin as well.
As insect repellent companies so helpfully put on the label, a spray that has 25 percent DEET has 75 percent other stuff. So what’s the other stuff?
Water: This one is kind of a no-brainer. All the insect repellents we looked at were liquid, and water makes up the base of that liquid. The DEET’s gotta be dissolved in something.
Ethanol, aka ethyl alcohol: Yup, this is the same stuff that you drink. (Don’t drink bug repellent!) The nice thing about ethanol is that it has a relatively low vapor pressure, which means it evaporates quickly. A bonus is that it makes an azeotrope with water, so when these two chemicals mix together in a certain ratio, the mixture evaporates at a lower temperature than water does by itself. That’s good for bug repellent, because DEET is really soluble in ethanol but not especially soluble in water. Chucking ethanol in there allows companies to use a higher percentage of water, which is cheaper than filling the bottles up with ethanol. It’s also less flammable. So it makes a repellent that costs less for you and poses less of a fire hazard. Win-win. According to the safety sheets, most DEET-containing repellents have anywhere from 10 to 30 percent ethanol. (But they don’t say exactly how much, since that’s apparently proprietary.)
If the spray is an aerosol, it also contains propellants, which help get the stuff out of the can. These components are butane, propane, and isobutane. You may have heard of them since they generally serve as fuels, in lighters and gas grills and such. They work as propellants because they have very low vapor pressures, which means that they each exist as a gas at room temperature, causing pressure to build up in an aerosol can. When you push the trigger, the pressure inside is higher than the pressure outside, and the stuff in the can comes rushing out. These propellants are obviously also highly flammable, so you should probably steer clear of any cigarettes before using a bug spray. Aerosol bug sprays have only small amounts of these compounds, though, around 1 percent.
Other other stuff: The ingredients above are in all bug sprays, minus the propellants if it’s a pump. But some other ingredients exist in only some sprays. The dry formulas tend to have several extras. S.C. Johnson, maker of the dry Off Deep Woods Insect Repellent VIII, is one of the few companies that actually list their ingredients on the Web (hooray). During my research, getting the ingredient lists from other companies was like pulling teeth. After talking to three people at Cutter, I finally got the whole list. Coleman, which makes our runner-up, took multiple emails and phone calls to respond at all. When I finally did get the PR person to respond, they would not tell me the whole ingredient list but said that High & Dry spray contained cornstarch, which is what produces that nice, dry, non-oily feel in all brands of dry sprays.
Among the ingredients in the Cutter and Off sprays is an emollient, basically skin spackle. Body lotions tend to have these; they make your skin feel smoother. Isopropyl myristate is in Off and polyethylene glycol-40 hydrogenated castor oil does the trick for Cutter. You also have magnesium carbonate, which Off says helps keep the spray from clumping up; you might know this compound as chalk.
Other ingredients keep the acidity of the sprays in check and prevent the can from rusting; in the Off spray, these are aminomethyl propanol and sodium benzoate. Aminomethyl propanol is also there for pH balance. Sodium benzoate is a food preservative. Meanwhile, Cutter uses triethanolamine and phosphoric acid to keep the pH of its repellent in check. To stop the evils of corrosion, it uses sodium benzoate, morpholine, and tetrasodium EDTA. That last one, the sodium salt of ethylenediaminetetraacetic acid, worries some people, but it isn’t absorbed through the skin very well, so the Cosmetic Ingredient Review panel generally sees it as safe.
Here’s how repellents don’t work: They don’t create some kind of force field à la the forest moon of Endor to your Death Star. To effectively repel bugs, you have to cover every inch of your exposed skin with the bug spray, which creates a kind of vapor barrier just above your skin, dermatologist Dr. Mark Fradin said. “Mosquitoes will bite an inch away from where there is no insect repellent,” he told me. “It’s not like perfume, you can’t put a little dab behind your ear and expect it to work.”
And if you have on tight-fitting clothing—that is, close enough fitting that a mosquito can probe through it—you need to spray it as well. This is why we eliminated repellents in the form of wipes or lotions; you can’t put these substances on your clothes easily. But this is also why experts say to wear loose-fitting clothing to avoid bug bites. If the mosquito can’t reach your skin, it can’t bite, repellent or not.
Repel Scented Family Formula, 15 percent DEET, scored third on Consumer Reports tests: The spray of this one went absolutely everywhere, and it puddled a lot on my skin. Once on, it felt very sticky.
Coleman 25% DEET Insect Repellent, 25 percent DEET, recommended by Vogue: The spray on this repellent was okay, but again it puddled on my skin. It was very oily both 10 and 20 minutes after application. It also gave me a slight rash.
Off Deep Woods Insect Repellent VIII (dry), 25 percent DEET, scored fifth on CR’s tests: This spray was the best in our initial tests, and it sent me searching for more dry-type sprays. It’s a great choice if it’s the only dry repellent you can find, as it was much less oily than all of the others in my initial test. However, it did end up being slightly oilier than our top pick, plus it doesn’t have a locking cap.
Off Deep Woods Insect Repellent V (non-dry formula), 25 percent DEET, #12 seller on Drugstore.com: Yuck. Very oily and stinky. It was quite puddly going on, and it still stank 20 minutes after application, even after I washed it off with soap and water.
Off Deep Woods Insect Repellent VII (non-dry formula, pump spray), 25 percent DEET, #22 seller on Drugstore.com: The kind we tested was a pump style, which is a lot harder to spray evenly than an aerosol. This formula puddled horribly but smelled better than most of the others. The scent was light, and barely detectable after 20 minutes. The repellent was still quite oily at that point, though.
Cutter Sport Insect Repellent, 15 percent DEET, #23 seller on Drugstore.com: This product went on puddly and took about five minutes to dry, which was about two to three minutes longer than the others. It was less oily than most others after 20 minutes, but still more oily than the dry versions.
3M Ultrathon Insect Repellent 8 (spray), 25 percent DEET, #25 seller on Drugstore.com: This repellent has a light, fresh scent that’s actually kind of pleasant. That’s the last pleasant thing about this spray, though. It was the most oily of the lot, and it was still wet and slippery 20 minutes after I sprayed it on.
Repel Sportsmen Dry, 25 percent DEET: This dry repellent felt mostly dry after 10 minutes and was undetectable after 20 minutes. It also had no scent that I could pick up on. It would have been our runner-up, but it’s really hard to find online. We had to buy our test supply from eBay.
Originally published: May 25, 2016