What's With Mosquito Repellent Patches?

I just saw an ad in my current Canadian Gardening magazine for a patch which claims to repel mosquitoes. Having an intense hatred for all biting insects, I was intrigued, though suspicious of its efficacy. The "OmeZone Insect Defend Patch" apparently contains thiamine (vitamin B1), which is released into your system through your skin. It starts acting within 2 hours and can deter mosquitoes for up to 36 hours, according to the ad. It is promoted as safe for children and pregnant women, which probably appeals to the people who are cautious about synthetic chemical repellents. It costs $6.95 for a pack of 5. My questions about the patch:
(1) How does it work? I have read that it essentially makes you appear stinky to mosquitoes. A repellent odor oozes out in your sweat, though this is not apparent to other humans.

(2) Does it work for all kinds of mosquitoes, including Culex tarsalis (spreads West Nile virus in this province), and the Aedes and Anopheles species? I can't find any published articles demonstrating its proposed effect. If it is effective, then why hasn't this been already used widely in prevention of malaria.

(3) Why not just take oral thiamine, if this purpose is to get it into your body and into your sweat?
Stewart C. Harvey, Ph.D. recommended 100 mg of vitamin B₁ as an effective mosquito repellent in a 2002 comment to the New England Journal of Medicine (not a study or review article). The oral thiamine is certainly cheaper. One major drugstore sells thirty 100 mg tablets for $5.41. I suspect the patch format fools the general public into ignoring the fact that this is still a drug acting on your body, albeit an essential vitamin. Perhaps the manufacturer aims to make the drug more long-acting by formulating it as a transdermal patch? In that case, I'd probably rather just take a few tablets of the thiamine over the course of 36 hours.

Other reasons to use a patch:
(a) you can't take anything orally because you are unconscious or don't have a functioning gastrointestinal tract
(b) you want to avoid metabolism of the drug in the liver (which does not apply to thiamine, but commonly applies to hormones) or
(c) you want a slow steady release of the drug over time (good for narcotics, nicotine, and hormones).

(4) Are there any good studies on humans that show that a thiamine patch is effective in repelling mosquitoes?
A search of OVID Medline with the search terms "mosquito" and "thiamine", limited to English and humans, revealed only 4 articles. Only one had an abstract (Journal of the American Mosquito Control Association. 21(2):213-7, 2005 Jun.). It described their study, where oral B vitamin complex supplements failed to have a relationship to the mosquito repellent qualities of the compounds released from the participants' skin. There were no articles on the transdermal (patch) use of thiamine.

A July, 2002 article in the New England Journal of Medicine has a very pertinent study of the efficacy and duration of action of several different repellents (thiamine not included), noting that 10% citronella oil can protect you for all of 19 minutes!

(5) Would I rely on this product to protect me in a country where malaria is endemic? Absolutely NOT!

Note these sad facts: More than 40% of the world's population is at risk of malaria, and more than a million people die of it each year. Malaria kills a child every 30 seconds: 90% of people who die from malaria are children not yet 5 years of age, and most (90%) of these deaths take place in sub-Saharan Africa. (Greenwood BM, Bojang K, Whitty C, et al. Malaria. Lancet 2005;365:1487-8.)

One website promotes this product by asking: "Are you planning to travel abroad to areas possibly infested by various insect populations?" and "Are you in an area where you know that mosquito-borne diseases are present?" Unless they mean northern Canada or parts of the USA, where the mosquitoes don't carry malaria, this is a reckless product recommendation. If I had to decide what product to use to prevent my own DEATH, I'd probably go with the one that has substantial evidence to prove that it works (DEET + prophylactic antimalarial oral medication + permethrin-treated bednets).

Aside from malaria, I know for sure that there are no published studies showing that this patch has any efficacy for prevention of yellow fever, dengue fever, Japanese encephalitis, or any of ther other mosquito-borne diseases.

(6) Should pregnant women use products like this because they are safer than the alternatives?
It should be pointed out that pregnant women need particularly good protection from malaria (DEET and certain antimalarials are okay), since malaria will kill a fetus and occasionally the mother too, since immunity is lower in pregnancy. Several deaths have occured in Canada due to misinformation on the prevention or treatment of malaria in travelers. If we are just talking about nuisance mosquitoes, then you may as well use any product that isn't known to be unsafe.

The Canadian Medical Association Journal published a critical review (DEET-based insect repellents: safety implications for children and pregnant and lactating women. August 5, 2003; 169 (3)) which concludes that "There is no evidence that the use of DEET by pregnant or lactating women poses a health hazard to unborn babies or children who are breast-feeding."
Another quote from the promotional website: "Just one small OMEZONE TM Defend Patch, applied discreetly on any hairless area of the body creates an invisible virtually impenetrable shield against the ill effects of mosquitoes and the diseases they may carry."

Yeah, well I'll bet that the mosquitoes probably find it hard to bite you THROUGH the patch. I propose that the application of several hundred patches, so as to cover every bit of exposed skin, would be effective as a mosquito repellent.

Bad, Bad Biting Bugs

Okay, let's be honest. The main thing I hate about Saskatchewan and the north is the bug cloud that descends on this place in the summer. Granted, bugs are common to the north across Canada, and that's why I will eventually move to a better place. And that won't be Winnipeg (I hear that mosquitoes are the provincial bird). Southern Saskatchewan has plenty of mosquitoes, but up here you have the thick-as-smoke blackflies and no-see-ums that taunt you and peer in your windows, shouting obscenities until you come outside and donate some blood. My trendy Canadian garden magazine ought to have an article on this. Instead, they have the chic urban Toronto couple with their black and white themed garden and matching poodles...hello???

No one denies that the bugs here are terrible. Local stores sell trinkets with a mosquito saying "Send more tourists, the last ones were delicious!" I fly frequently in small planes across the north for my job and we're told that if you are to survive a crash, it is still possible to die by insect bites, so be sure to bring repellent in your survival gear. Black flies are known to kill large game animals and livestock. This is disgusting. The picture above is of my swollen right eyelid after a black fly bite last summer. This was more dramatic-looking but less painful than the one in my ear canal.

This is another challenge of gardening in the north. How to handle it?
(1) Insect repellents - this year I am going to try out a "natural" option, a spray product called "Bite Me", containing various oils including lemon. It smells FABULOUS but I have yet to see if it works as well as the gold standard, DEET. If you live in a West Nile affected area, the benefits of DEET may outweigh its small risk. As of yet, West Nile hasn't made it this far north. I have used heaps of DEET sprays in the past, applying it to hands, ankles, neck, face, and lower back (because mosquitoes get you when you bend over) as well as all over my clothes.


(2) Proper clothing - NO shorts, NO spandex, NO tank tops. The idea is to cover as much skin as possible, which has the bonus of preventing any sunburns! I love my Tilley hat and heavy cotton pants with reinforced knees from the army surplus store. I wear one of those thin running/cycling jackets (you know, with the "tuxedo tail" to cover your backside) over a breathable shirt. I usually wear a hiking boot, but I have been thinking about finding a pair of Wellies.

The aim is to have loose-fitting clothing so that there is a space between the clothing and your skin, otherwise the mosquitoes easily bite you through your clothes. Last year, a new gardener to the north complained to me about all the mosquito bites on her backside. This is the problem with sweat pants or any stretchy clothing; the minute you bend over, the fabric is close to the skin and the bugs get a tender treat. Unfortunately, I prefer fitted gardening gloves and the mosquitoes easily bite through them, just like they bite through my socks. I cover these areas with repellent.

Now this is sexy clothing indeed:

(3) Environmental factors - gardening in the rain, a stiff wind, or the very hottest time of the day will avoid most biting bugs. This requires true gardening grit, and the neighbours will think you're insane.

(4) Start a bat or dragonfly farm - or at least, we are bat and dragonfly friendly. These friends eat enormous amounts of biting insects. I heard that there was a dragonfly breeding program in Manitoba last year. This sounds better than fogging whole towns with pesticides, although I can understand the frustration!

One last note -- if you have pets in the north, do NOT shave them in the summer. Remember, black flies can kill moose, and they certainly can make your sled dog miserable, especially if they have no hair to protect them. Our dog hides in her house on bad days.