Dan's Outside

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How DEET Works

The most common (and only effective, in my view) mosquito repellents are based on a chemical known as DEET. As is sometimes the case with things like this, apparently scientists have known that DEET does work, but did not know why.

The old theory was, as I understand it, that DEET somehow “jammed” the mosquitos’ sensory system in a way that made it impossible to detect human skin. This sort of makes sense if you have ever observed how mosquitos respond to normal skin and DEET treated skin: in the former case they land and chow down; in the latter they may get close but they don’t usually even land. (The buzz still annoys the heck out of you, but at least you aren’t getting bitten.)

New research suggests a simpler process is going on. Basically, DEET smells bad to mosquitos so they avoid it.

While I’m on the DEET subject, a few other points based on my own experience. You may already know some of this, but perhaps the info will be useful to some who don’t.

“Back in the day” a lot of people got the “100% DEET” (or nearly 100% DEET) versions of the repellent, on the theory that the stronger the solution the better it would repel the little bloodsuckers. Turns out that this wasn’t quite right. It only takes a little bit of DEET to work effectively – and the 100% solution tended to go on way to strong is some places and not distribute to well to other places. Eventually manufacturers and users figured out that a lower percentage of DEET in a spreadable creme would work more effectively.

I haven’t been keeping careful track of these things, but this year when I bought a new supply I found several products that claim to be long lasting or to release slowly over time. This makes sense, as even in the dilute creme form the repellent sometimes seemed to wear off too quickly. From what I can tell from the newer versions that I’ve used this summer, there really is something to the claims of longer lasting protection.

Finally, DEET is poisonous to humans. Don’t overdo it, and do be careful about ingesting the stuff. Many years ago I made this mistake and the results were not pleasant. We encountered truly awful mosquito conditions at Booth Lake in the Yosemite high country – so bad that we slathered on the DEET (in the old, undiluted form) and mostly tried to stay in the tent. The problem occurred when we had burritos for dinner – as we handled and ate this dinner we apparently transferred some of the DEET to our mouths, and the result was not fun.


August 18, 2008 - Posted by | Commentary

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