Look, I’m neither for or against it. Don’t have an opinion yet, nor an agenda. However, the facts are:
1. Is it “completely inactivated” (de-emphasis mine) in individuals with a hyper-sensitivity to it?
2. No skin oils in bronchials right. Well known inhaling it can cause problems, especially among asthmatics.
3. Yet, so gentle even a child can use it to de-louse. Though cases of contact dermatitis are known to occur. Not everyone reacts the same.
4. Like the idea of Googling… Googled “Permethrins” and found a number of hits – some for topical products; others about the health hazards. Now, some of the hits referred to laboratory experiments, mainly on rodents, but also on dogs. I always take these lab studies with a grain of salt, since some of them feed the chemical to the lab rodents, or dose it at very high levels. Don’t think any hiker is gonna’ drink Permethrin products. However, dogs showed some undesirable side effects. Now dogs share ~94% of their genetic material in common with humans. Any Doctor of Veterinary Medicine will tell you that many drugs we take were approved and first used on dogs due to some basic similarities in physiology.
So, here is an excerpt from just one “hit”. It doesn’t tell the whole story and inhalation is certainly different than topical application. Every Permethrin insecticide I’ve ever smelled was aromatic – if it makes it to the nose, there’s a good chance that it makes it into the lungs. Sounds like there must be some actual research behind statements like in this excerpt:
“… Permethrin was mutagenic (damaging to genetic material) in three tests with human cell cultures, one with hamster cells, and one with fruit fly larvae. In cultures of human lymphocytes (white blood cells), permethrin exposure caused an increase in chromosome aberrations, chromosome fragments, and DNA lesions….”.
Now that don’t sound good!!!
Maybe oils deactivate it, but just don’t inhale while applying it.
5. Issues are concentration and exposure. Best to minimize both.
6. Here’s a Pharmaceutical precaution regarding topical Permethrin cremes and shampoos:
“What side effects can this medication cause?
Although side effects from permethrin are not common, they can occur. Tell your doctor if any of these symptoms are severe or do not go away:
* skin irritation
* rash
* redness
* swelling”
Sounds like not everyone’s skin oils “COMPLETELY DEACTIVATE” permethrins. FDA does NOT require precautions about undesireable side effects to be listed unless they are exhibited by at least a very small percentage of study participants.
Bottom Line:
For me, the jury is not back with a verdict on this one. It’s not toxic enough so that it can’t be used in a human de-lousing shampoo, yet known side-effects , are known to occur, both when inhaled and when applied topically.
Now, it certainly could be that some permethrin is deactivated by skin oils – I don’t know; guess I didn’t spend enough time reading the Googled “hits”. Denying that there are absolutely no risks since skin oils “COMPLETELY DEACTIVATE” permethrins is simply telling ourselves a fable to alleviate worry. The facts don’t back it up. However, there are many more toxic chemicals we can come into contact with or inhale – some regularly. As in most chemical reactions, there is a limiting reagent. Can we be sure that we are producing sufficient oil to deactivate all of the permethrin. The concept of limiting reagents is basic chemistry. This brings to mind another quesiton, if it’s deactivated, does it still work to repel the skeeters? I don’t know since I don’t know the chemistry involved, but I wouldn’t think so. Permethrin has a modus operandi based upon its chemistry. If body oils “COMPLETELY DEACTIVATE” it, then it longer demonstrates that modus operandi since it has been chemically changed. This being the case, how does it still work? Answer, probably is, that it wouldn’t, hence some must be left unchanged inorder to work, or at least converted to a related compound that still demonstrates the toxic effect – just reasoning “out loud”, so to speak, here.
To each their own. Hike your own hike.