Friday, January 29, 2016

The Mosquito Vampire Diaries

From an article I wrote a few years ago:

Summer is here and so are the mosquitos. Every year we humans try our best to ward off these little vampires. Every year we get bombarded with social media memes, emails and news reports about how to protect ourselves. We are offered a wide array of options from home-made concoctions, to sprays we can buy at a pharmacy. So what works? What is safe?

First off, let’s look at what attracts mosquitos to humans. Skeeters are attracted to warmth, body odour, moisture and the exhalation of carbon dioxide. Yes, mosquitos can smell carbon dioxide. So what we want issomething that can block their ability to sense those things from us.

DEET has been around for 50 years and is one of the most studied repellent ingredients. It is the most widely used as it is the most effective. According to the New England Journal of Medicine,
"DEET is far less toxic than many people believe. Adverse effects, though documented, are infrequent and are generally associated with gross overuse of the product. The risk of DEET-related adverse effects pales in comparison with the risk of acquiring vector-borne infection in places where such diseases are endemic."

It is interesting to note though that not all mosquitos are created equal, and DEET does not seem highly effective against the mosquito that transmits malaria.

Next we have a whole slew of items that work from varying degrees of “somewhat” to “almost not at all” according to sources. Even the most effective of these, though, pales in comparison to the effectiveness of DEET. These include herbal oils, garlic, and Avon Skin So Soft.

Garlic oil rubbed on the skin, has been shown to have repellent properties, although the smell may also repel humans as well. Some people claim that eating garlic will do the same. In various studies though it has shown to have no effect at all when ingested.

Other herbal oils such as cinnamon, lemon, citronella and castor (mixed with a carrier oil such as olive or sunflower) have been shown to be somewhat effective. The problem though is that these are not necessarily safer. It is often misconception that "natural" is safer.

Avon Skin-So-Soft is a bath oil that has been claimed by some users to work. In a study done by Mark Fradin and Jonathon Day of the University of Florida, they looked at the effectiveness of 17 marketed mosquito repellents including the Avon product. They found Off! Deep Woods with DEET effectiveness lasted 302 minutes while Skin-So-Soft only lasted about 10 minutes. Avon claims their product lasts 3 hours. Consumer Reports reported the product working 1 hour. With such varied reports, it may be wisest to assume an average of up to 1 hour and 20 minutes.

Bug zappers are a common backyard sight. Generally, though, mosquitoes (and other biting insects) make up less than 1 percent of the bugs zapped in these. Many beneficial insects, on the other hand, do get zapped like dragonflies which prey on mosquitoes. Also bats and colonial purple martins will eat mosquitos, but that only makes up a small part of their natural diet.

A popular social media meme suggests using Listerine or dish soap in bowls around the yard or spraying around the home. These are supposed to knock the little critters dead. According to Snopes.com these are pretty much useless.

So it can be a little confusing as to what to use.

Obviously DEET is the best choice for safety, cost and effectiveness. But if you are concerned about that, some of the herbal oils may work for you. To learn more contact your local health unit and follow guidelines such as those listed at Health Canada.

Have a safe and happy summer!

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