Insect Repellents: Which Work Best?

We are in the thick of mosquito season, and I’m sure we all have our favorite bug-killer products, from zappers to plug-ins to that Chinese spray in those tall greenish bottles. But what really works? I found a nice new resource from the good folks at the doctor-oriented Prescriber’s Letter; they have a free detail-document discussing what really works against skeeters. They endorse the 2 major chemicals that are approved by the U.S. Environmental Protection Agency: DEET and Picaridin. Here’s a long snippet:

Products containing DEET (OFF!, Cutter, etc) are some of the best for repelling mosquitoes and ticks. These products can contain different concentrations of DEET. Higher concentrations last longer, but they don’t work better. DEET 30% lasts about six hours, and DEET 10% lasts about three hours. Pick a product with up to 30% DEET for adults and kids over two months.

Some product labels won’t actually say DEET, so look under the ingredients section of the label for its chemical name, N,N-diethyl-m-toluamide or N,N-diethyl-3-methylbenzamide.

Picaridin (Cutter Advanced, Natrapel, etc) is a good alternative to DEET for repelling mosquitoes and ticks. It works as well as similar concentrations of DEET and doesn’t irritate skin or damage plastic or clothing. As with DEET, products with higher concentrations of picaridin last longer than those with lower concentrations. Choose a product with up to 20% picaridin for adults and 5% to 10% picaridin for kids over six months.

Oil of lemon eucalyptus (Repel Lemon Eucalyptus, etc), also known as p-menthane-3,8-diol or PMD, is a good choice if you want a “natural” or plant-based repellent for mosquitoes and ticks. Its effect lasts for up to six hours, but it hasn’t been proven safe for kids younger than three years.

Other plant-based products, such as those that with soybean oil (BiteBlocker, etc), last for around four hours for mosquitoes and around two hours for ticks. Products with citronella oil (Buzz Away, etc) generally work for even less time.

You can read the full document here: Detail-Document: Prescriber’s Letter. You can read more reviews from WebMD; and the excellent Consumer Search has a nice review of which brands to buy.

Safe For Children? Yes, It Is

DEET has always had a stigma for many, especially as the smell is strong, but also due to the relatively common skin irritation issue. However, no major review has found any major problems. The EPA reviewed DEET’s status in 1998 and still found no major toxicity issues with normal use. In 2007 they again addressed this:

Using DEET on children

DEET is approved for use on children with no age restriction. There is no restriction on the percentage of DEET in the product for use on children, since data do not show any difference in effects between young animals and adult animals in tests done for product registration. There also are no data showing incidents that would lead EPA to believe there is a need to restrict the use of DEET. Consumers are always advised to read and follow label directions in using any pesticide product, including insect repellents.

The American Academy of Pediatrics has a position paper approving the use of DEET in children over 2 months:

Insect repellents containing DEET (N,N-diethyl-m-toluamide, also known as N,N-diethyl-3-methylbenzamide) with a concentration of 10% appear to be as safe as products with a concentration of 30% when used according to the directions on the product labels. DEET is not recommended for use on children under 2 months of age.

DEET-containing products are the most effective mosquito repellents available. DEET also is effective as a repellent against a variety of other insects, including ticks. It should be used when there is a need to prevent insect-borne disease. The concentration of DEET in products may range from less than 10% to over 30%. The efficacy of DEET plateaus at a concentration of 30%, the maximum concentration currently recommended for infants and children. The major difference in the efficacy of products relates to their duration of action. Products with concentrations around 10% are effective for periods of approximately two hours. As the concentration of DEET increases, the duration of activity increases; for example, a concentration of about 24% has been shown to provide an average of 5 hours of protection.

I also found a terrific review from 2009 which lucidly describes the ever-present worry about DEET. The gist of the article is that picaridin may be more tolerable to most people than DEET — although it may not be as effective as DEET for some mosquitos. Here’s one good quote:

For decades, DEET has faced public scrutiny regarding the health risks it poses to consumers. However, several studies indicate that DEET has a remarkable safety profile. For instance, a lab study conducted by Antwi et al. found that there were “no significant toxicological risks from typical usage of [DEET and picaridin]”25. Furthermore, a safety re-assessment conducted by the Environmental Protection Agency in 1998 deemed that “the normal use of DEET does not present a health concern to the general population”26. Much of the controversy associated with DEET comes from its safety record concerning children. The Department of Health and Human Services, Agency for Toxic Substances and Disease Registry (ASTDR), states that seventeen cases of significant toxicity from DEET exposure have been reported during the period between 1961 and 2002. Fourteen of these cases occurred in children under the age of eight—the most frequently reported symptoms were lethargy, headaches, tremors, involuntary movements, seizures, and convulsions27. Although these cases should in no way be deemphasized, they are likely attributed to inappropriate usage such as repellent ingestion27. Addtionally, the number of reported cases is miniscule for a forty-year span.

Where To Buy?

Picaridin doesn’t seem to be available in China, so if you prefer this, you should stock up in your home country. Our pharmacy sells a spray of 25% DEET, which should be good enough for everybody. Most clinics and pharmacies carry some type of spray — just remember to look for the active ingredient on the label. If you can’t read it, or it mentions citronella or “plant-based” but no more details, then you might want to hold off and look for more certain labels. After all, you don’t want to get malaria on your annual vacation just because you bought some locally made mystery spray which wears off after an hour — if it works at all.

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4 thoughts on “Insect Repellents: Which Work Best?”

  1. hmmm. We avoid DEET, especially for kids. DEET is the main active chemical in mosquito repellent products.

    New research shows it to be neurotoxic, meaning it may cause damage to the brain and other parts of the nervous system.

    David Guiterrez reports on the latest findings:
    &lt ;>

    from his article "The Environmental Protection Agency has a review of deet's safety planned for 2012."

  2. Sorry, your link didn't work. But I understand parent's very common concerns about DEET, and I just revised my post and fleshed out more of the data for people to decide. It's important that people use effective protection against mosquitos, especially for children. Malaria by itself kills 1 million people a year — 85% of which are children under 5 years. Many countries and the WHO prefer picaridin over DEET, but it may not be as effective for some mosquitos. I don't see picaridin available in China; does anyone have access? What about Oil of lemon eucalyptus, does anyone see that here in Beijing?

  3. Oh. something about the formatting, here it is again (or google "Deet Finally Exposed as Neurotoxic")

    from the study: "These findings question the safety of deet, particularly in combination with other chemicals," said researcher Vincent Corbel of Institut de Recherche pour le Developpement in Montpellier.

    from the article: "In experiments performed in cockroaches and rats, the researchers found that deet blocked the action of the neurological enzyme acetylcholinesterase. This is the same mechanism that causes the toxic effects of popular carbamate and organophosphate pesticides, as well as chemical weapons such as sarin and VX nerve gas. This may mean that deet repellants are actually insecticides and could damage the human nervous system."

    Well, fortunately there are some good natural alternatives. Most of us only ever have to deal with a few bites a week while in bed. So there are screens for cribs and bedtops. Once in a while one still gets in, though, and when she does, she has a field day.

    When we were on vacation in Thailand, we quickly learned that it is really quite miserable after dark, even with repellent (they get in your face- ewww) so most nights we just didn't go out after dusk. We were tired, had 3 kids under 6 and all ready for a good supper and jacuzzi bath!

    For repellent though, regular Eucalyptus oil is definitely available at WHS. Citronella oil has been at De Run Wu before, not sure about now. They also have Citronella oil in glycerine soaps. Citronella oil on those little stroller /bed rail patches works pretty well (I get mine from Shanghai Toy Club but u could make your own easily). Regular Lemon essential oil may work. Seems like the Lemongrass oil really helped when we were in Thailand. They burned some over a candle, in an essential oil burner (few drops of oil in a lot of water, over a candle) and the mozzies never entered the room. I just remembered that fact. We never had a single mosquito in the room. In Thailand. Unbelievable. The stuff must work! Le Meridien said they'd gladly ship from their little gift shop- maybe I should call them and get some Lemongrass oil…hmmm…

    Natural products like Buzz Away, Natural Newborn and Bite Blocker use combinations of even more types essential oils to confuse the mozzies. (Vanilla, Lavender, and the ones listed above). The scent is nice but can be a little overwhelming to sensitive-nose types like me or if you have an aversion to any of the components. Still, we've used them in-house for years.

    Vitamin B1 also is supposed to work really well as a deterrent. Adults and kids can take a B Complex vitamin or B1 liquid before bed. B1 is excreted out the pores, and the mozzies hate the smell (virtually undetectable by people). There are also little B1 patches for babies (Don't Bite Me Patch technically they are approved for 1 year and older).

    I haven't needed to try it yet, but I investigated it and discovered that one could make their own b1 patches: buy B1 liquid from Iherb and put it on a bandaid with aloe vera gel (the patent for the baby patches had B1 liquid, with aloe vera to transport it into the cells and presumably into the bloodstream, the excess dumped out the pores).

    hope this helps someone.

    Deet might be effective, but IMO applying a neurotoxin to lil ones, in order to prevent a rather unlikely event, seems unwise to me. I like the Precautionary Principle anyway …and dear readers there's more to it than the popular adage "An Ounce of Prevention is better than a Pound of Cure"

  4. Dear madam.sir i have used ur web site to get some info on the treatment for malaria but i need to reference the web site therefore i require the fallowing information the author and the editor of the website. kind regards serah

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