Here is an interesting article on DEET: Evidence for inhibition of cholinesterases in insect and mammalian nervous systems by the insect repellent deet.
These findings question the safety of deet, particularly in combination with other chemicals, and they highlight the importance of a multidisciplinary approach to the development of safer insect repellents for use in public health.
http://www.biomedcentral.com/1741-7007/7/47/abstract
Claude
If you are really interested in digging below the surface in this paper, let me offer a few points. First, the paper does not question the safety of DEET. It shows one possible receptor for DEET in humans; the binding between DEET and this receptor is EXTREMELY weak. Second, most chemists would consider DEET to be a very simple molecule. Generally speaking, simple molecules are promiscuous molecules: they bind to nothing at low dose, and everything at high dose. At the concentrations they used in the paper, I would guess that DEET would show binding to MANY receptors. This is inconsequential because the concentrations used in the study could NEVER be achieved in a person under normal circumstances. A binding constant of 500 micromolar (from the paper) is roughly 10,000 times less potent than what most pharmaceutical scientists would consider a starting point for interesting activity. To make an analogy, ibuprofen has some level of acute toxicity. But if that toxicity becomes significant at 10,000 times the normal dose, it's not something I'd worry about, because it's not possible for me to ingest 20,000 tablets of ibuprofen. (Note: I'm just making an analogy, I have no idea what the acute toxicity of ibuprofen is.) Third, the authors SPECULATE (wildly, I might add) a possible interaction between DEET and cholinesterase inhibitors, and suggest that more studies are needed. I disagree. If cases of acute toxicity towards DEET were common (they are EXTREMELY rare), I would say, yes, we should try and understand its mechanism of toxicity. But these cases are so rare and the circumstances so varied, I think it highly unlikely that any general trends will be realized. It's a waste of time. We already have all of the clinical data we could ever need.
Finally, any good solvent will "melt" plastic (not really melting, actually dissolving). Not really indicative of toxicity, but I do keep my ropes away from the stuff. And I promise that lemon eucalyptus spray contains chemicals. Many chemicals. "Natural" is not equal to "safe". Aconitine, for example (
http://en.wikipedia.org/wiki/Aconitine), is available at many herbal medicine shops. Yikes.