If 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.
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.
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