Molecules: You'd better learn to live with them.
The ubiquitous active ingredient in insect repellent, DEET, is a great solvent. Anyone who's spent much time outdoors has discovered this empirically, as he's inevitably seen it fog polycarbonate glasses, dissolve a gear sack, or destroy $500 raingear.
DEET-based insect repellents come in a variety of strengths, from 10-25% creams, to bottles of pure DEET. It's probably the only organic solvent that comes in a bottle designed for intentional skin application:
For quite awhile, the presumed mechanism of action for DEET was blocking the receptor for things like octenol. Just last month in PNAS, though, researchers showed that DEET is truly repellent to insects.
Medicine & Health
Environment
Comments
Believe me, it doesn't repel Culicoides Impunctatus.
Posted by: Dunc | September 10, 2008 9:12 AM
Seems like I heard it is an excellent skin penetrant, second only to DMSO. True? Does it also have the ability to shepherd large molecules through the skin like DMSO? rb
Posted by: arby | September 10, 2008 12:40 PM
(Hot) DEET is the miracle solvent of last resort. (For uncooperative inorganics deep eutectic 1:2 choline:urea or ethylene glycol. For cellulose, 1-ethyl-3-methylimidazolium acetate. For silica, aqueous ammonium hydrogen bifluoride plus a drop of Dawn dishwashing liquid or KOH in hot ethylene glycol. For transition metals, Rauchfuss' elemental sulfur in N-methylimidazole). Dissolve the world!
OTOH, pig studies show DEET permeates skin quite well. HMPA and DMF are mildy carcinogenic, NMP recently got a poor evaluation. DEET might not be entirely benign.
Posted by: Uncle Al | September 10, 2008 2:01 PM
It's too bad that Canada has restricted DEET concentrations to 30%, killing the better repellents on the market.
Posted by: Rick Pikul | September 10, 2008 2:26 PM
DEET/DMT was banned for large-scale use as a pesticide (agricultural, primarily) for a number of good reasons - primarily because, once it got into the water cycle, it caused thinning of bald eagle eggshells that nearly led to the extinction of the species. It's still available (widely) for individual use, but should be avoided if at all possible, because it does a lot more than keep the bugs off you. It is a terribly toxic substance to most creatures who might be sharing the wilderness with you, from insects and spiders up to birds and rodents.
Just thought I'd throw that in there.
Posted by: Aeryn987 | September 10, 2008 7:07 PM
I guess I'll take my chances with DEET, tis the season for those nearly invisible tick nymphs around here. I have grown to hate them over the years. Like, a lot. rb
Posted by: arby | September 10, 2008 7:32 PM
It's also a helluva weedkiller, by the way. Or grass killer, or flower killer. I guess what I'm trying to say is, it's a helluva broad spectrum herbicide. When I spray my socks and cuffs this time of year, I do it along a weedy brick path. Doesn't kill the roots of course, but it browns the tops of weeds in nothing flat. A weed injurer, if not a killer. rb
Posted by: arby | September 10, 2008 7:37 PM
Aern987: You're thinking of DDT.
Posted by: Size | September 11, 2008 11:08 AM
Ah yes, quite a solvent. Back in the day, we used to buy a 100% Deet repellent that REI sold under the name "Jungle Juice." It did a great job of repelling not only mosquitoes, but also northern Michigan's famous black flies--so small they could come through a tent screen and send us running for a cheap motel. But we also had a car that for the rest of its life carried my hand print on its hood.
Posted by: Ann | September 11, 2008 11:06 PM
Am I? >.> ... That'll teach me not to check my facts.
Posted by: Aeryn987 | September 12, 2008 4:50 PM
Ah, I recall the Boy Scout camping trips of my childhood, where my fellow Scouts would amuse themselves by spraying shots of insect repellent at a lit propane stove. Fortunately, the Lord looks after fools, drunks, and children, and being two out of the three, we apparently were allowed to sneak by.
Posted by: Adam | November 19, 2008 3:29 AM