What's the straight dope on insect repellent sprays?

OK, having spent the better part of Labor Day being a walking buffet lunch for the local mosquito population while hiking in the hills, I’ve resolved that this weekend I’m bringing some insect repellent with me. Do any of the various sprays on the market (including those with DEET) actually repel mosquitos, or do they simply mask your scent so the mosquitos don’t know you’re good eating?

In short, assuming these sprays work at all, do I need to cover every square inch of my body (including the top of my head, which seemed to be a favorite dining spot of last week’s univited guests to Chez Barry), or is it enough to just spritz it on a few choice locations (arms, neck, legs) and trust that it will provide a zone of protection?




They don’t actually repel the insects, but rather interfere with their mechanisms of finding a target. Ideally, they don’t realize you’re there, so they don’t bite.

I have had some experience with the mosquitos of Massachusetts and Rhode Island, and they are by far the worst I have ever encountered. Standard issue Cutters or Off was, as I recall, good for about 5 minutes (here in Texas they’re good for 1 - 1 1/2 hours).

Wherever you are, you have to apply the repellent anywhere you might get bitten. There is no general zone set up by the stuff.

I haven’t tried many DEET-free repellents. I have tried 100% DEET, and it is nasty stuff. It can dissolve certain clothing fibers and plastics, it can cause skin irritation, and it stinks. Try it if, and only if, you’re completely desperate.

The worst mosquitos I ever experienced was when doing reforestation near Fort Nelson, BC. It rained nonstop for about a week, and then turned sunny and warm. The mosquitos were so thick that you could see a black smudge trailing behind people as they walked along. If you walked too slowly, it could be difficult to avoid inhaling them. Truly unpleasant. Break out the DEET, though, and they were merely an annoyance, instead of sufficiently nerve-wracking to drive a person insane.

In the course of my tree-planting career, I did try some non-DEET repellants, and none of them ever worked worth a damn, particularly the citronella based ones. DEET, particularly the high concentration varieties, does work, and works very well. I never experienced it to be effective for only 5 minutes, though I was admittedly using the 100% concentrate stuff. It would generally last 4 hours or so (bottle says 6-8, which it probably would under less demanding circumstances, assuming you didn’t sweat it all off). It is also, as kelly5078 points out, nasty stuff.

You do have to apply it to anywhere that is likely to be bit, but I can offer a tip or two to make it less unpleasant. First, temperature permitting, wear long pants and long sleeves. Physical barriers work even better than repellant. Choose clothing with a tight weave - mosquitos will bite through cotton tshirts like they aren’t there, and can even get through jeans without trouble, but more closely-woven material like that found in army pants defeats them, and is cool enough to wear even on warm days. And even if they can bite through a long-sleeved tshirt, at least you’ll be spraying the repellant on the shirt instead of directly onto yourself. I also found that spraying repellant onto a bandana and then wearing the bandana hanging out the back of a hat was quite effective at keeping the dratted things off my ears and the back of my neck.

Well, let’s just assume (and not just for the sake of argument, I am sorry to say) that I tend to sweat profusely when hiking. And let’s also assume that my hiking gear of choice is jeans and a cotton t-shirt. Am I doomed? Or can spraying enough DEET-based repellant on my clothing to (a) prevent the mosquitos from biting through the cloth and (b) make up for the fact that anything I spray on my exposed flesh will likely be washed away in short order due to perspiration? And does it matter whether I buy an oil, water, or alcohol based spray?

We’re not talking about visible clouds of mosquitos here, BTW.


No, not doomed. Jeans, while walking, are plenty of protection. The fabric moving relative to your skin completely foils them. Just sitting around, they can get through, but not if you’re hiking. If you’re sweating profusely, then the tshirt will probably assist in the efficacy of the repellant, since what you spray on it won’t wash away. So your back should be fine, and that’s the most annoying area, since you can brush away the mosquitos on your arms/face much more easily. If you go for the highest concentration of DEET in a spray (~35%, IIRC), then you should be fine. Might have to respray your arms/back of neck/etc every hour or so. Not sure about the oil/water/alcohol thing, as I don’t recall ever seeing the stuff classified that way. I generally just grabbed the Muskol or Deep Woods off the shelf.

Mosquitoes LOVE me … I’ve had success with two brands of repellant - Off Skintastic (believe it or not) - and Watkins brand (which contains DEET). I prefer the OFF because the warnings are less scary, and it’s very non-irritating. I have to reapply it every couple of hours, but it’s worth it. I have sensitive skin, and it doesn’t bother my skin at all. When I use it, mosquitoes leave me completely alone.

The Watkins brand isn’t available in stores - only through a Watkins sales representative (Watkins is kind of like Tupperware or Avon in that way). It also apparently works to prevent bites from blackflies, etc.

Good luck!

DEET works best, higher concentrations of DEET work better.

I’ve also had good luck with Off Skintastic, which is lotion based. We have mosquitoes here in Alaska that are approximately the size of F-16s, but with a different tail structure. Out in the bush, nothing much is going to keep the clouds off you, but for hiking and general outdoor activity in established areas, this stuff works well. Spraying clothing, including your hat, is a good idea.

I am a mosquito magnet, no doubt about it. But I’ve had a lot of success with Deep Woods Off, even in the swamps of Florida in the summertime. If I apply a thin-but-thorough layer to every bit of exposed skin I get almost no bites at all for at least a couple hours, although I’m not usually out for much longer than that, so I don’t know how long the protection lasts. And I tend to hike wearing shorts, too (when it’s 90 degrees and 85% humidity, you do what you can to keep cool). It’s amazing how effective a little DEET can be. I spray down my clothes and my skin, and apply it to my head/face by spraying a small amount onto my hands and rubbing it on. I may get cancer before I’m 40, but at least I won’t be itching.

I’ve seen some sprays or lotions advertised as having 100% DEET, but it sounds like the concentration of DEET has more to do with how long it lasts than with how effective it is. Off Skintastic, for example, seems to only have 5% of DEET, and Chefguy, at least, finds it effective.

Neither my wife nor I are fond of excessively dousing ourselves with chemicals, so maybe I’ll see if I can find some of that Skintastic stuff on the way home from work today.

(I apologize in advance if this sounds like an ad)

I have found the best non-DEET mosquito repellent. It really really does work. I live outside of Houston in an area that is rampant with the vile creatures. I have tried everything in my quest to avoid using DEET based products. This is the first summer that I have used the product and we really have put it to the test. We spend a lot of time outdoors and we’ve had an exceptionally wet summer. I even use it on the dogs to repel mosquitos and black flies.

Here’s a link to the website:
Bite Blocker

Question: Is there such a thing as a fragrance-free DEET repellant?

So far ther does not seem to be any repellant I ca use without getting rather serious burns and risk permanent scarring (yes, I’m that allergic to artificial fragrance.)

So does anyone know of a DEET-based repellant I can test? Or is it in itself the same type of chemcial that would turn me into a giant, walking blister?

I directly spray Off (with DEET) onto the mosquitos on my back porch and it kills them within seconds, so maybe it’s more than a repellent/mask?

I found Deep Woods Off (around 20% DEET) to be fairly effective againt Massachusetts mosquitos, but if you miss a spot they’ll find it. Don’t forget that they can get through all but the thickest clothing.

As I understand it, mosquitoes find you by sensing a combination of things you exude, including heat, moisture, CO2, and chemicals in your sweat. If you sweat more, all of those exudations increase, plus you may “sweat off” your repellent; therefore, the more you sweat the more easily they find you.

Repellent technically works by confusing them, not repelling them, as noted above. It does not work by somehow “sealing” you off from the world. But the more you use, the better it works, to a point. I find that it depends on the local mosquitoes and their cussedness as to whether or not you need to cover every inch of exposed self.

We discussed related stuff in the Do citronella candles work? thread.

There is a New England Journal of Medicine article concerning the efficacy of DEET and a few non-DEET products. This is the study cited in the article Telemark gave us a link to.

In sum, the study found that few of the non-DEET products are worth anything, but the product called “Bite Blocker” that siberia mentioned does seem to be roughly as effective as lower concentrations of DEET. It’s effective long enough that it may be useful: 16 to 195 minutes (vs. 200-360 minutes for OFF Deep Woods 23.8% DEET, the best performer in the study).

A copy of the study is available on the Bite Blocker website for free; ignore the highlighting added by the Bite-Blocker people and you’ve got a nice impartial piece:

Note that DEET comes in many different concentrations. You’re right, godzillatemple, it looks like the NEJM study found that the higher the DEET concentration, the longer it stays effective. Concentration increases of only 4% are meaningful. Concentrations of 95% are available (though they typically have names that imply they’re 100%!), but they may be more toxic than strictly necessary to get the job done (and the NEJM study didn’t test them). If you find you need to use the 95% stuff, I’d think you should be extra-careful.

“Controlled-release” DEET formulations apparently don’t work any better or longer than similar concentrations of non-“controlled release” DEET. Wristbands (with DEET or anything else) are useless. Citronella is minimally effective, working for up to 20 minutes if at all. I’ve had some luck with herbal sprays containing neem oil, but haven’t found any studies about it. When it works for me, I still need to reapply it every hour or less.

In all cases, avoid getting anything containing DEET on any sores or scrapes or razor burn, up your nose, in your eyes, or especially on your lips, which it will numb. It’s harder to avoid this than you might think. To avoid it, you should wash your hands after you apply DEET-containing lotions or gels, and refrain from sticking your wedding ring up your nose until after you’ve washed your hands.

If you use sprays, don’t breathe it and don’t apply it to your face (like, duh). Cover your face with something if you apply it to the top of your head.

I got me some Bite Blocker at Whole Foods but haven’t had an occasion to use it yet. I avoid DEET less because I’m worried about toxicity and more because the stink bothers me so much – it gives me headaches. I’m with Eats_Crayons: is there a fragrance-free DEET out there? And, if so, is it noticably less ghastly-smelling than the regular stuff?

If you can stand the dorkiness factor, I recommend protective net clothing, especially the hats. Mosquitoes can of course stick their nasty little proboscii right through net to bite you; the net items work by being loose and standing farther than a proboscis-length away from your skin.

I’m in the US, and I use Walgreens Family Insect Repellent (unscented, with aloe vera). It seems to have a very slight smell that goes away after it dries. “Off” also has an unscented product.

Googling “deet unscented canada” turned up a mention of Cutter Unscented on this page: http://www.canada.com/calgary/specials/consumer/030508.html

As to your reacting just to the DEET, it can’t be ruled out. Maybe your local store will let you test a spray on a small area of skin.

You should use permethrin on your clothing. Just spray some on your clothes, and it will last for weeks. Do not use DEET under your clothes. I’ve read that all you need is no more than a 40% solution of DEET.

I do a lot of bird watching in the woods, swamps, etc., and do not use DEET. I’ve tried various plant oils without too much success. But I’d rather suffer an occasional inconsequential fly or mosquito bite than risk DEET. I’ve had a discussion on that before on this board, with the consensus being that DEET has no risk, and plenty of cites to back it up. I’m really not convinced. Our bird expert and leader, who birds every day, does not use DEET. He uses permethrin on his clothes and is convinced that cactus oil works. I’ve tried cactus oil and it doesn’t work for me.

For gnats, nothing beats Skin-S0-Soft, and it works, I think, because gnats cannot penetrate the emulsion. Doesn’t work for any other insects because they all are too big.

I mentioned the consensus to our illustrious leader of the safety of DEET and he was not convinced either. He cited instances of some people having side effects, and one lady in particular had headaches with its use.

Well, here’s a report from the field for whatever it’s worth…

The wife and I went hiking on Saturday and brought some Off Skintastic with us. We doused ourselves liberally and reapplied often (especially me, since I sweat a lot more than her).

The good news for me is that I didn’t get any mosquito bites on my arms, head and neck this time (last week, those were the areas where I got chomped upon the worst). The bad news is that I still got multiple bites on my lower legs, between the top of my socks and the bottom of my shorts. I also doused that area liberally, but I probably didn’t reapply it down there as often as I should have.

My wife, on the other hand, got a single bite on her arm, which is all she got last week with no repellant, so it’s hard to make a case for significance.