Diluting Deet?

[Brad Groves]

No worries, Dean. Incidentally, I once knew an asthmatic who smoked, and claimed strong sensitivities to odors.

Ben et al, on how mosquitos find you: "Mosquitoes locate bloodhosts by scent, sight and heat. From 100 feet away (30 meters) mosquitoes can smell your scent, especially the carbon dioxide (CO2) you exhale. Biting flies are even better; they can smell their prey from 300 feet (100 meters) away."-http://www.control-mosquitoes.com/#mf11

From another site, "The main chemical they respond to is carbon dioxide which is mainly given off by our breath but is also released through our body as well. Other chemicals such as 1-octen-3-ol which is also given off as an alcohol, it’s given off in our breath, and certain acids as well which are found in quite high amounts on your feet. These types of chemicals are very attractive to mosquitoes."-http://www.thenakedscientists.com/HTML/content/interviews/interview/909/

I concur: most research shows that DEET isn't significantly carcinogenic. My point is more like this statement in layman's terms: "In truth, scientists have not established a direct link between DEET and cancer. The Centers for Disease Control and Prevention (CDC) classifies DEET as a group D carcinogen — meaning it's not classifiable as to human carcinogenicity. In simple terms, that means that they can't say it causes cancer, but they can't say it doesn't, either."-http://adventure.howstuffworks.com/outdoor-activities/hiking/deet3.htm

There's plenty more info out there, but in short (and in my experience), bug repellants work primarily by repelling bugs. They find you pretty much through your breath. When I wear bug repellant, I watch them hover over my skin, then fly away. (Or hover over my sprayed clothes, then fly away.) So they're coming in for lunch, but then turn away… which seems to reinforce the repellant (not masking) action of the dope. Like I said, I've had the best luck w/Ben's 30 in some pretty horrid conditions. But in the worst conditions, the best answer is total body coverage in clothing.

Incidentally, once they tend to hone in on your scent they go for primary heat sources… highly vascular regions. Which is why they bite the back of your knees, around your ankles, wrists/hands, head/neck.

Perhaps an aerosol can and a mini bic could be a good deterrent and a bit of fun? (Just kidding, folks… bad idea!)

Just spitballin': what about cutting some DEET into some Permetherin? That said, Perm. (at least in the versions I've seen) isn't supposed to come in direct contact w/skin…

[Dean F.]

Yeah, everything I've ever heard indicates that Permethrin is only for application on clothing, too.

And calling DEET a class D carcinogen is essentially equivalent to calling it non-carcinogenic. If any carcinogenic effects are so low that nobody can find a hint of a causal link with 100 million regular users in the US (let alone occasional users), well, good enough for me. Heck, nickel metal is worse than that- and almost any metal item that you wear day to day contains nickel. Watchbands. Steel jewelry, belt buckles. Earrings. Buttons and snaps, zippers.

[EndoftheTrail]

Gee, Dean, no wonder sperm count's been down world wide the last couple of decades!!

[Gordon Smith]

I don't like DEET. It's not a safety concern for me, I just can't stand the smell. For the last several years I've been using picaridin products with varying results. I started out using Cutter Advanced, which is only 7% picaridin, and it did seem to work, though not as well as DEET. Then I switched to Sawyer's picaridin products that are 20% picaridin. I found that at that concentration it's very effective, perhaps not more so than DEET, but at least as good. It's not odorless either, but to my nose it is far more tolerable. Plus it isn't greasy like DEET and it doesn't melt plastic. I'm a happy convert. YMMV.

G

[Dondo .]

I've had the same experience, Gordon. After trying the 7% version, I gave up on it, but when the 20% concentration came to the US, I gave picaridin another try. At this point, I have enough confidence in it to leave my small backup vial of DEET behind.

[james w glenn]

Ive used staight skin so soft in midgy areas. The little buggers crawl all over you but cant seem to get enough traction to bite. For skeeter hell, add DEET until YOU hit your comfort level. Bugs can pass on plenty of diseases but I find that its more of a matter of how much can I take before I am driven "buggy"

[bj bretzke]

Deet, as a complex hydrocarbon, is some gnarley crap material. All you have to do is do a label count like any product. Some bug sprays are as wimpy as 3.5%. (Childrens bug spray/Sunscreen. The only Deet I have found that works most of the time is the 99% formula that is considered carcinogenic. Not only that but there is a record of soldiers who have not been exposed to deet for months because of geographical location actually dying for lack of a better reason when exposed upon their homecoming……..

[Ben Crowell]

I guess this is somewhat of a necro-thread, but thought I'd add some info I gleaned.

At a concentration of 5%, it only lasts about 1.5 hours. http://www.deetonline.org/faq.php#q9 At 100%, it lasts about 10 hours. To me, it's a huge advantage to be able to apply it once and then not have to worry about it again. No way do I want to stop every 1.5 hours to reapply it. So if you feel the way I do, the technique is to put a tiny amount of 100% deet on the back of your hands, and apply it to your exposed skin.

If all you care about is minimizing pack weight, then you actually get more protection per unit pack weight when it's diluted. The ideal thing would be to carry the 100% stuff and dilute it with water, which you don't have to carry from trailhead to trailhead. DEET is not very soluble in water, but that's OK, because you don't have to actually form a solution. The basic technique is to squeeze out a tiny amount into a baggie, then add some water, and mix it up enough so that it forms an emulsion. The mixture will stay emulsified long enough to allow you to apply it. Some people do the mixing in the palm of their hand, but then you tend to get it in your food. You can apply it with the back of your hand, or you can use a baggie as an appicator.

100% DEET will not eat nylon, silnylon, or polyethylene. It will eat polystyrene, ABS resin, styrofoam, most synthetic fabrics, and polycarbonate. So the things to worry about are generally bear canisters, your car's steering wheel, and possibly your clothes. You typically don't have to worry about it eating your backpack, sleeping bag, or tarp.

DEET works simply because mosquitoes dislike the smell: http://entomology.ucdavis.edu/news/DEETresearch.html , Zainulabeuddin Syed and Walter S. Leal, "Mosquitoes smell and avoid the insect repellent DEET," PNAS.org. Older statements about blocking their sense of smell, etc., are incorrect.

[Bob Gross]

Whenever possible, I like to avoid getting it on my skin. However, it needs some warmth to vaporize and do any good. So, I generally drop a little (directly from a bottle) along the collar and armpits of my wool shirt, and whatever body heat is there can do it.

–B.G.–

[James D Buch]

Permethrin – New Source of Safety Data

Permethrin, an insecticide, has been used and debated as an anti-insect treatment for clothing, including backpacking. This useage is most often based on 0.5% solutions, although some use higher concentrations.

It is common for someone to allege that it "might be unsafe to use this insecticide in contact with human skin".

"The Johns Hopkins Pills & Medicines – 3,000 prescription and over-the-counter medications."
ISBN 978-1-57912-359-8
Copyright 2005

On page 620 is Permethrin – sold as a generic topical antiparasitic for ridding the head of lice — including children's heads. Brand names are Nix and Elimite.

Elemite is sold as a lotion containing 5% permethrin to be applied directly to the scalp.

[The Nix directions limit the exposure on the skin to a certain number of minutes – to be followed by washing it off the scalp][Actually, the Rid box may be what I looked at in the drug store. The permethrin concentration was 0.5%]

The Johns Hopkins book cites side effects

" SIDE EFFECTS
Serious
No serious side effects have been reported.

Common
Burning, itching, numbness, rash, redness, stinging, swelling, or tingling of scalp. In most cases such symptoms are mild and temporary: notify your doctor if they are more troublesome or if they persist.

Less Common
No less-common side effects have been reported."

==========================================

By searching for the pharmacological recommendations for the drugs, Nix and Elimite, you can obtain your own information on side effects of permethrin applied directly to human scalp skin.

The section on how the drug works is below.

" How The Drug Works
Permethrin is absorbed into the bodies of lice, where it blocks nerve activity, ultimately causing paralysis and death of the lice. (The drug has no such toxic effect on humans.) "

Bottom Line

Follow the safety instructions on any bottles of permethrin you buy for the purpose of treating garments with insecticides. Follow the military treatment guidelines for the application of high concentrations of permethrin. If the instructions say not to get it on your skin, feel free to follow the instructions.

[EndoftheTrail]

Permethrin comes in different applications — for clothing, for plants, etc. For applying to clothing — the reason you don't want to apply to skin directly is NOT because of any danger to you, but because of ineffectiveness!

Permethrin meant for clothing is designed to bond with clothing. Applied to clothing, Permethrin is harmless and effective. However, it will not bond with your skin, meaning if applied directly to skin, it will simply be harmless — and ineffective.

[Ben Crowell]

Benjamin Tang wrote: "the reason you don't want to apply to skin directly is NOT because of any danger to you, but because of ineffectiveness!"
Hmmm…here's a fact sheet:

http://npic.orst.edu/factsheets/permethrin.pdf

It says, "The dermal LD50 for permethrin in rabbits is over 2000 mg/kg." The "over" makes it ambiguous. But if the LD50 was equal to 2000 mg/kg, then you could get killed by getting 4-5 oz of it on your skin.

It also says, "Dermal exposure to cats and dogs may cause temporary paresthesia and neurological signs…"

This is all for extremely high doses, but I don't think it's accurate to say that the stuff is "harmless."

"DEET is supposed to mask you — as if you weren't there. It does NOT repel or kill skeeters!"
Your information is out of date. It turns out that it works simply because mosquitoes dislike the smell: http://entomology.ucdavis.edu/news/DEETresearch.html , Zainulabeuddin Syed and Walter S. Leal, "Mosquitoes smell and avoid the insect repellent DEET," PNAS.org

[EndoftheTrail]

Ben:

Take a can of Repel Permanone. The net weight is 6oz (170g) — of which just 0.5% is Permethrin. 0.5% of 6oz is a mere .03oz. of Permethrin per can!

I have a hard time imagining anyone spraying a whole entire can onto himself (or herself) all at once. But using your numbers above (4 or 5 oz), that person will need to spray 133 to 167 entire cans all at once to get the precious 4 to 5 oz. of Permethrin to potentially remove himself (or herself) from the gene pool…

Methinks you're assuming the product you buy is 100% pure — and thus one bottle is enough to kill. Not so.

Finally, I look at this the same as with most everything else. Take most anything to the extreme and we can get ourselves into trouble. We drink water everyday and it is perfectly safe doing so. And yet, we know water too can kill us if we drink a couple of gallons all at once! But that's so totally extreme (and preventable) that none of us is ever paranoid about it.

[James D Buch]

If we assume that the 2,000 mg/kg or 2 grams/kg figure resembles an LD50 that even remotely scales to humans…..

Then a 75 kg person would need 150 grams or about 5 ounces of Permethrin to cause death. The 0.5% (or 0.005) commercial clothing spray then would require 5 oz/0.005 = 1,000 ounces of the 0.5% spray or 1,000/7 = 142 cans of this spray to do you in.

I had to take the calculation and do it slow several times to make sure I had it right.

We do know that the basic LD 50 number we began with isn't really an LD50 number, but something that is less than whatever the real number is.

I realized my own focus on skin protection was from an instruction sheet for the use of PERMA-KILL® 13.3% PERMETHRIN SOLUTION for use in treating US Army uniforms which required rubber gloves. The instructions for Sawyer 0.5% solution do not mention rubber gloves at all.

All the documents I have reread emphasize that the permethrin is INEFFECTIVE if applied to the skin.

I could find lots of "assertions" that permethrin is formulated differently for agricultural applications than the stuff for clothing, but I couldn't find anything which indicated in what way this would happen. The permethrin preparation for hair uses a different solvent formulation than for spraying agriculture; the hair product has been described as a cream which certainly is a different solvent than a water based spray. There are isomers of the compound, however.

A patent was recently granted for a "long life method of permethrin insecticide to clothing" at:
http://www.freepatentsonline.com/7625411.html

"Insecticidally treated fabric having improved wash durability and insecticidal efficacy and method for its production"
United States Patent 7625411

"wherein said fabric retains said permethrin at 90% of the initial load after 50 launderings"… So, this is really long lived stuff, potentially. But it doesn't look DIY with a bucket and plastic baggies.

[EndoftheTrail]

James:

You are right. The sheer number of cans required to kill oneself is astronomical. After reading your post, I've corrected my own calculations up above — but our message is the same, in response to Ben Cowell's post. The Permethrin available in stores really are harmless to humans for all intent and purpose.

[Author]

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