Do mosquito repellent wrist bands work?

wristbandIf you don’t know if commercial mosquito repellents work, how can authorities provide useful advice to the community? What about non-topical mosquito repellents? How do you help the community make informed decisions on how to choose and use mosquito repellents effectively?

I’ve written about mosquito repellents on a number of occasions. The most popular post on my blog has been one describing how we test new repellents. That post was promoted by the enormous support received by a crowdfunding campaign by the developers of the Kite “mosquito repellent” patch that raised over $550,000 back in August 2013. There is a steady stream of new repellents in the news, either newly published research on active ingredients or new approaches to formulations and delivery systems. What was most appealing with the Kite patch was that is wasn’t a topical formulation but a “spatial repellent”. All you needed to do was put a sticker on your shirt you’d be protected from biting mosquitoes. An effective non-topical mosquito repellent would be a great asset in our battle against mosquito-borne disease.

Much of the research I do with mosquito repellents is directed towards better informing local health authorities on what works and how it should be used. My development of guidelines on mosquito repellent use came from the paucity of information provided by local health authorities. Health authorities generally provide the right advice, just not with enough detail that allows the public to make informed choices on mosquito repellents and how they should be used.

repellent_spraying_webb

Topical mosquito repellents are the most commonly used and widely distributed in Australia. These products, particularly those containing DEET or picaridin are most commonly recommended by health authorities

One of the most common questions I’m asked at public events is “do those mosquito repellent wrist bands and patches work?”

In 2010, I tested a product currently registered for use in Australia by the APVMA for use against mosquitoes. This was a plastic wrist band impregnated with peppermint oil. The results of the study were published in the 2011 volume of General and Applied Entomology. All papers in that volume are now freely available for download.

We tested the bands in laboratory conditions against the mosquito Aedes aegypti. This mosquito is one of the major vectors of dengue and yellow fever viruses internationally. It is also the most common species used in laboratory assessments of mosquito repellents due to its persistent biting behaviour and preference for humans.

The bands were tested to determine if any protection or repellency was provided against the mosquitoes compared to a DEET-based topical repellent. Although fewer mosquitoes landed on arms with the wrist bands compared to arms without wrist bands, there was no complete protection provided (as observed with DEET-based topical repellents). In fact, even on arms with wrist bands, beyond a small area around the band, the reduction in landing mosquitoes further up the arm was only marginally better than on arms without the wrist bands.

In short, while there was a reduction in total bites in close proximity to the bands, the bands we tested won’t prevent all bites. They won’t completely prevent bites on the arms wearing the bands and there is certainly no evidence that other parts of the body will be protected. They won’t create a “halo” of protection against mosquito bites around you.

There aren’t a lot of published studies investigating these “non-topical” repellents. There are a few “wrist band” and “patch” type devices available but all generally contain a botanical based active ingredient. In Australia, there are no DEET-based spatial repellents registered (to my knowledge). Studies from overseas have yielded mixed results. The level of protection (if any) provided is generally dose-related. For the most part, these devices have been demonstrated to assist in reducing the number of bites but not protecting you from all bites. Similarly, studies investigating the effectiveness of burning “mosquito sticks” demonstrate that while fewer bites are received, there is no complete protection provided.

repellentrack

A summer approaches, the local hardware stores boost their stocks of Christmas lights and mosquito repellents

The results prompt an interesting question for health authorities (as well as regulators of mosquito repellents). Is it good enough to simply reduce the number bites, do you really need to prevent all bites?

My personal feeling is that you need to prevent as many as possible. Transmission of mosquito-borne pathogens such as Ross River virus, dengue virus or West Nile virus isn’t dependent on the number of bites. A single mosquito bite is all it takes. It may be true that the more bites you receive, the more likely it is that one of those mozzies will be infected but what if it is the first bite of the day that infects you?

So, do these devices have any use? My advice is to go with a DEET-based topical repellent. However, in some cases there may be some benefit in using a repellent wrist band to protect the hands if you’re undertaking an activity where the topical application of repellent may be considered inappropriate (perhaps fishing?). You could even wear these devices around your ankles to prevent bites but if you’re in a region where dengue or Chikungunya viruses are active (see here and here), I’d always recommend a topical product.

So, in answer to that commonly asked question, “Do mosquito repellent wrist bands work?”, I’d say they may offer some very limited protection but they are an ineffective way to prevent mosquito bites compared to a DEET or picaridin based topical repellent.

Here is the abstract of our paper:

A wide range of insect repellent formulations, as well as active ingredients, are currently registered for use in Australia. While topical repellents are most common, there are also commercial products in the form of wristbands impregnated with botanical extracts that purport to repel mosquitoes. In laboratory tests, wristbands impregnated with peppermint oil were tested against the mosquito Aedes aegypti to determine their efficacy in repelling mosquitoes from the forearms of human volunteers compared with a commercial DEET-based topical repellent. The wristbands failed to stop landing by the mosquitoes, although the mean landing rate of mosquitoes was significantly lower on forearms in the presence of the wristband compared with untreated controls. The mean landing rate of mosquitoes on forearms treated with DEET was significantly lower than those of forearms in the presences of the wristband. The results indicated that while wristbands impregnated with botanical products may assist in repelling mosquitoes, their inability to completely protect individuals from mosquito bites suggests that they should not be recommended for use in areas of endemic or epidemic mosquito-borne disease.

The full paper [PDF] can be downloaded for free here:

Webb CE and Russell RC. (2011) Do wrist bands impregnated with botanical extracts assist in repelling mosquitoes? General and Applied Entomology 40:1-5. PDF

[UPDATE 25 February 2015] It is interesting to note that in the U.S., the Federal Trade Commission has charged a manufacturer of mosquito repellent wrist bands with “making deceptive, unsubstantiated claims” regarding the effectiveness of their product. It will be interesting to see how this decision impacts the availability of these products in North America.

Want to learn more about the amazing world of Australian mosquitoes? Check out “A Field Guide to Mosquitoes of Australia” out now through CSIRO Publishing. Over 200 pages containing a pictorial guide to almost 100 different mosquitoes along with tips on beating their bite and protecting your family from the health risks of mosquitoes. You can order online or through your favourite local bookstore or online retailer.


Read more at The Conversation: Are mosquito coils good or bad for our health?


Read more at The Conversation: What can I eat to stop mosquitoes biting me?


Read more at The Conversation: The best (and worst) ways to beat mosquito bites



 

Busting five myths of mosquito repellents

repellent_spraying_webbAfter a record year of West Nile virus activity in 2012, North American health authorities are on alert as the peak season of mosquitoes approaches. As of 16 July 2013, a total of 23 cases of human disease, including three deaths, had already been reported by CDC.

In many regions across the US, local mosquito control districts engage a range of strategies to reduce mosquito-borne disease risk. These may include broad scale insecticide use or the release of “mosquito fish” into derelict backyard pools. However, the first line of defense against biting mosquitoes remains the use of topical insect repellents.

In North America, the CDC provide detailed information on mosquito repellents but there still seems to be confusion amongst many in the community looking for alternatives to “chemical repellents”. These repellents are often perceived to be unsafe. For an Australian perspective, I’ve put together some guidelines on mosquito repellent use that provide a few more details than typically found on the websites of local health authorities.

In my experience of trying to promote the use of “known to be effective” repellents, I still find that there are many misconceptions and misunderstanding of how these products should be used. Below are the five myths I most commonly experience when it comes to the use of mosquito repellents.

Myth 1: Natural must be better

It isn’t surprising that most people associate “natural” products with better health. Many people perceive mosquito repellents derived from “natural” products, such as plant extracts, to be healthier choices. However, when it comes to mosquito repellents, there is clear evidence that these perceived “healthier” choices may not provide the best outcomes.

Studies have repeatedly shown that the most effective repellents are DEET and picaridin. DEET, in particular, has been shown to be very effective. Picaridin is pretty good too. Both products have shown to be effective in local field-based tests.

Unfortunately, many, many studies throughout the world have shown that botanical based repellents provide substantially less protection against biting mosquitoes than DEET or Picaridin. Products containing citronella, lavender, peppermint and Melaleuca oils are widespread and are often promoted as “DEET-Free” alternatives to the recommended repellents. There are many botanical-based insect repellents listed in the patent literature.

Essential oils of Australian native plants provide significantly less protection than DEET-based repellents. Expert review panels have suggested that products containing plant extracts should not be recommended in areas of endemic mosquito-borne disease or when biting mosquitoes are abundant.

It is important to remember that botanical-based repellents WILL provide some limited protection against biting mosquitoes. The biggest problem is that they will need to be reapplied 3-4 times as often as even a low dose DEET-based repellent to provide comparable protection. Botanical repellents may be fine for a quick trip to the backyard to hang the washing out but not for a long session of gardening or if you’re off for a hike.

It is also important to remember that using undiluted essential oils can also pose an important health risk, particularly in young children.

I often wonder if Koalas are bitten any less by mosquitoes than other Australian mammals given the amount of Eucalyptus leaves they consume! (Photo by DAVID ILIFF. License: CC-BY-SA 3.0)

What about “Oil of Lemon Eucalyptus”? That’s a botanical repellent and authorities recommend it against West Nile virus right? There is often some confusion regarding this product. It is not the essential oil, but rather a byproduct of the distillation process of the leaves of Corymbia citridora. Commonly known as PMD, it has been shown to be as effective as DEET (although generally requiring higher doses for comparable protection) and is recommended by the CDC in North America. The recommendations by CDC of this product should not be seen as an endorsement for other “botanical based” repellents.

Myth 2: Stronger repellent = fewer mosquitoes

This is probably the most common mistake made when choosing a repellent. The “strength” of a repellent (i.e. the concentration of active ingredients) doesn’t determine how many mosquitoes are kept at bay. It determines the duration of protection provided. It basically determines how long you are protected from biting mosquitoes.

The majority of published studies (the classic “arm in cage” style experiments) investigating the efficacy of repellents analyse the results in two ways, mean repellency rates (a comparison of how many mosquitoes land on a treated arm compared to an untreated arm) and mean protection time (for how long are all mosquito bites prevented). While the marketing companies may be interested in claims like “over 80% of mosquito bites prevented”, given that it only takes one mosquito bite for a pathogen to be transmitted, I’m hoping to prevent ALL bites! We should be far more interested in protection times than repellency.

Myth 3: Chemical repellents are dangerous

Both DEET and picaridin are considered safe. If used as directed, DEET-based repellents pose no substantial health risk. Despite being used by millions of people every year, there are few examples of reported serious adverse health impacts in the scientific literature.

There are many stories circulating about mosquito repellents having an unpleasant smell or creating an unpleasant feeling on the skin. There are also reports about damage to clothing and plastics in some instances. Some of these reports may be true but are most likely related to high concentration formulations. In the US, there are many brands available that contain over 95% DEET. In the vast majority of situations, however, most people would find that an approximate 10% DEET formulation would work perfectly well and not be associated with any of these unpleasant characteristics.

Myth 4: Apply repellent like perfume

A neighbor took great pleasure in telling me how ineffective mosquito repellents were. Repeatedly. One afternoon I saw him applying repellent to his children. The aerosol was sprayed around in the air above the kids as they jumped up and down. There was no way that the repellent was going to work.

While there is still some debate as to how DEET prevents mosquitoes bites, or how the response of mosquitoes to DEET is influenced by previous exposure or infection with a pathogen, we do know that to get the best results, the repellent should be applied as a thin covering on all exposed skin. It is for this reason I personally think creams and liquids are the best repellents to use.

Don’t apply repellent like a perfume. A spray “here and there” won’t work. Spraying it on your clothes won’t work either. Apply it in the same way as you would a sunscreen but keep in mind that you won’t need to apply it quite so often.

As summer approaches, the shelves of hardware stores and supermarkets are filled with various repellents, insecticides and traps. Some work better than others.

Myth 5: These gimmicks really work!

If it sounds too good to be true, it probably is! Gimmicks such as traps, ultrasonic devices and smartphone apps all sound very appealing if you find that putting on repellent is a bit of a hassle. Unfortunately, there is little scientific evidence that any of these will protect you from mosquito bites.

There is even a pill, recently approved by Canadian Health Authorities, that purports to only take 30 minutes to protect the swallower from mosquito bites. An excellent blog post, “Insect repellent you can eat – but does it work?”, refuting the claims of this product, is here. Also check this nice piece from 2012, “Homeopathic Insect Repellent: Is there anything the Natural Health Products Directorate won’t approve?

In short, there is nothing you can eat or drink that has been scientifically proven to prevent mosquito bites. That’s right, not even vitamin B.

In summary, the mosquito repellents widely available in North America, Australia and many other parts of the world are perfectly safe to use and can be effective in preventing mosquito bites. Many of these (and more) urban myths will persist for some time and perhaps it is time health authorities worked harder to communicate the benefits and effective use of the products available.

UPDATE: Thanks to BugGirl and Laurie Sullivan for the suggested tweaks!

Want to learn more about the amazing world of Australian mosquitoes? Check out “A Field Guide to Mosquitoes of Australia” out now through CSIRO Publishing. Over 200 pages containing a pictorial guide to almost 100 different mosquitoes along with tips on beating their bite and protecting your family from the health risks of mosquitoes. You can order online or through your favourite local bookstore or online retailer.


Read more at The Conversation: Are mosquito coils good or bad for our health?


Read more at The Conversation: What can I eat to stop mosquitoes biting me?


Read more at The Conversation: The best (and worst) ways to beat mosquito bites