DEET (insect repellant) …. Dangerous?

Factual Questions
1

With lots of media attention on West Nile virus these days, I have seen or heard several statements that the best protection is to avoid mosquito bites by using insect repellants containing the chemical DEET. These statements say to apply the DEET to exposed skin or to clothing, but NOT to apply it to skin covered by clothing. The implication is that this would somehow be harmful.

How or why would the use of DEET on skin covered by clothing be harmful? If it is safe to use directly on exposed skin, how would covering it with clothing make it less safe?

2

From what I understand, DEET is a known carcinogen. It’s use on skin covered by clothing would be redundant and, therefore, unadvisable.

3

From the USEPA site…

Myth: DEET is highly toxic and causes cancer and genetic mutations

“In studies using laboratory animals, DEET generally has been shown to be of low acute toxicity. It is slightly toxic by the eye, dermal, and oral routes and has been placed in Toxicity Category III (the second lowest of the four categories) for these effects.” “DEET has been classified as a Group D carcinogen (not classifiable as a human carcinogen).” “DEET is not mutagenic under the conditions of the test assays. …the results are all negative.”

· Myth: DEET is toxic to and causes seizures in children

“Based on the existing reproductive and developmental toxicity data, there is no evidence that would lead the Agency to believe that DEET is uniquely toxic to infants and/or children.” “Seizure coinciding with DEET use can be expected, given an estimated 15,000-20,000 afebrile (occurring without a fever) seizures in children (aged 0-19 years) estimated annually and an estimated 17 million children using DEET perhaps 10 times a year.” “Given only 14 to 32 cases since 1960 (the first case was reported in 1961) and 50-80 million people using DEET each year, the observed incidence of recognized seizures is about one per 100 million users.” “There is no compelling information that exposure to DEET is causing an appreciable number of seizures, and data from animal studies do not support or predict symptoms experienced by children exposed to DEET.”

4

DEET is the most effective repellent safe for application to human skin and has been thoroughly studied for 50 years, and is certainly a better choice than leaving yourself open to West Nile.

5

I remember buying repellant about 15 years ago that was 100% DEET–it worked better than anything I’ve ever used. I was bug-free in the Adirondacks in August.

6

**Lieu’s ** cite does not say it is entirely safe. Further, it is recommended that no formula greater than 10% DEET be used on children. It is also recommended that no more than 25% be used on adults.

To answer the OP, and it has been answered, is that there is no point in putting DEET on skin which is already covered by clothing. That is redundant. The implication is not that it would be harmful.

I, personally, don’t use DEET, and I go birding (bird watching) in the woods every Wednesday morning and occasionally at other times. I use presently something called “Buzz Away,” which was recommended by Dr. Mercola on the web. It is a citronella formula, and I have not had much success with citronella in the past, but this works. The New England Journal of Medicine did a study on the effectiveness of different plant oils and found “Bite Blocker for Kids” (made from olive oil) to be the best (but not as good as DEET). The guy that leads the bird walks on Wednesday swears by cactus oil. I used that without good results, but he said that the spray I used is no good and I have to use the salve. The ingredients in both show no difference, but there has to be a difference in order to make the spray. It is in the “inert” ingredients that make the difference, and I think that is the case with citronella formulae. I tried to look up the results of the NEJM, as it was reported in Consumer’s Reports, but I need to be a subscriber to get more details.

7

Correction: The reference to the NEJM study wasn’t in CR, but in a newsletter. I don’t recall which one since I gave it to my birding friend and I receive several. I also want to add that IMO, the risks of getting sick from the West Niles Virus is less than the long-term ill effects from DEET. Even if bitten, most people do not get sick from the virus.

8

"I also want to add that IMO, the risks of getting sick from the West Niles Virus is less than the long-term ill effects from DEET. "

Interesting O, given that the ratio of deaths from West Nile Virus in the U.S. to deaths from DEET in the U.S. is getting stratospheric and that there ARE no long-term ill effects from DEET.

9

"I also want to add that IMO, the risks of getting sick from the West Niles Virus is less than the long-term ill effects from DEET. "

What about the risks of Dengue Fever or Malaria, in regions where they are prevalent?

10

Redundant in what sense? That untreated clothing is itself sufficient to prevent bites? lieu and barbitu8 have apparently never been bitten through clothing.

Redundant in the sense of use on skin covered by treated clothing? Agreed (mostly).

Nevertheless, from the way this was presented on TV – “Use directly on exposed skin or on clothing, but NOT on skin under clothing” – the implication (to me) was one of some degree of harm, not redundancy. Of course, there was no further explanation. Hence, the OP.

Further enlightenment, anyone?

11

I would just like to point out that DEET can melt plastic, while it may not be “highly toxic” the fact that it can chemically affect plastic tells me that it can’t be worry free.

That said, under certain conditions I have had to use 100% DEET, applied to skin, and re-apply it every 3-4 hours. It sure beat the hell out of being turned into a dry husk by million, if not billions, of malaria carrying(Possibly) mosquitos.

12

A couple of observations:

The last report i heard (admittedly, a few days ago) put this year’s death toll attributed to the West Nile Virus at 11. How does that compare to this year’s death toll attributed to DEET?

This is very interesting considering the last time i purchased bug dope lotion that contained DEET (roughly 2 weeks ago), it was packaged in a plastic squeeze bottle. Under what conditions does it melt plastic?

13

Under almost any conditions. Find yourself a cheap watch like a Swatch and spray the repellant on the face and strap and see the damage that occures. The plastic lens on my Mag Light is also pitted and scarred thanks to insect repellant.

14

Wear thick enough clothing.

How do you know? “Stratospheric”??? 11 deaths are stratospheric???

In some areas of the world, such as where malaria is present, DEET may be an acceptable alternative. But the malaria paraiste is not West Nile Virus.

15

The Mayo Clinic website ( http://www.mayoclinic.com/invoke.cfm?id=DS00438&si=1480) states:

16

Certainly DEET dissolves certain types of plastic. And not certain others (as is shown by the fact it comes in plastic packaging). Let me tell you about the time the lid of my insect repellent came off in my brand new and very expensive backpack and dissolved the waterproof lining…

But I don’t think, Adam Yax that one can validly assume that just because a particular substance dissolves a particular thing, it is harmful to humans. Water dissolves lots of stuff. You don’t think that’s harmful do you? We are not made of plastic.

17

I don’t mean to offend barb and so I hope that barb doesn’t take this as anything but constructive criticism and a further clarification and elaboration of arguments already in this thread but your last two posts suggest a less than firm grasp of arithmetic and logic.

“How do you know? “Stratospheric”??? 11 deaths are stratospheric???”

No one suggested that the number of deaths attributed to WNV in the U.S. is other than small. If you will read my post, I suggested that the ratio of WNV deaths to DEET deaths was exceedingly large. The ratio is either 11:0 (which is infinity) or 11:? where ? is a very small possibility and hence the ratio is stratospheric.

As for your Mayo Clinic website post, “Most people with the virus either don’t have symptoms or have only a mild illness”, I will have to leave it up to you to explain why you believe that the ratio of symptomatic to asymptomatic WNV infections has anything whatsoever to do with how much of a threat WNV is. (Hint, most people involved in automobile accidents are not injured or are only slightly injured, yet many people counsel safe driving.)

18

According to sources I’ve read, increasing the DEET concentration is non-effective beyond 40%. So, those 100% DEET creams are way overkill. Apparently, 40% DEET will repel bugs just as well as 100% DEET, so there’s no reason to expose yourself to that much of the chemical. I’ll see if I can find the cite.

Jman

19

barbitu8 & Yeah,
This site Has a bit of information on the dangers of DEET. From what i can gather on a quick perusal, there are 6 deaths attributed to DEET since 1960 (although one of these deaths concerned a man choking while eating as a result of seizures from DEET). It also contains the information that lieu posted in regards the hazards to children.

In regards the deaths, i think that it is significant that there are 11 deaths directly associated with the West Nile Virus this year alone while there are only 6 deaths associated with DEET in the past 40 years. Logically, this would lead me to the conclusion that the West Nile Virus is more of a health hazard than DEET.

In regards the children aged 0 - 19, the incidence rate of seizures resulting from the use of DEET at 1 in 100 million is significant as the entire population of the U.S. is roughly 300 million. Additionally, taking the extreme number of 32 cases since 1960, works out to less than 1 case per year.

I am not, by any means, attempting to persuade you to abandon your choice of repellant or to say that DEET is 100% safe. Rather, i’m just pointing out that DEET is safer than contracting the West Nile Virus. Personally, i use a product that contains DEET at about a 25% strength but use a non-DEET product on my 2 year old son. I’m not concerned about the affects of DEET, per se, on my son, but rather the fact that, whether it’s the DEET or the delivery medium (the non-active ingredients), most products are irritants and tend to hasten the effects of the sun on his little body.

As to the second question of the Original Post, i would venture that it is possible that DEET or the non-active ingredients are irritants and are more irritating to the skin if covered as the irritant cannot readily evaporate. My assumption is based on anecdotal (although personal) evidence: I have used citrus-based solvents for a number of purposes and never has a serious problem in regards contact with exposed skin resulted from such use. On one occasion, i sat on a bucket and pressed the nozzle of the can with my thigh, soaking my jeans just above the knee. Within 5 minutes, it felt as if my leg were on fire. My only relief came after i stripped off my jeans and douched myself off with the water bucket. Of course, this happened in public and would have been terribly embarrassing if it weren’t so damn funny. Lucky the nozzle wasn’t pointed at my crotch when i sat…

For clothing, i’ve always preffered wearing chamios shirts and have found them to be effective against mosquitos without being unduly cumbersome. Even then, i sprayed all areas (of the shirt) that were ‘tight’ such as the shoulders and elbows as well as the wrist vents as these were the ‘chinks’ in the armor.

20

It’s my understanding, due to a Scientific American article (which I can no longer find,) that DEET’s effect is from its vapors, not from contact. It doesn’t make you taste bad, it just confuses Ms. Skeeter. In other words, you don’t have to have the stuff all over you. You only need to include it in your aroma. A few squirts of DEET is enough.