I’m puzzled that the links provided don’t actually imply that pyrethrins are especially toxic and I am afraid that people are being discouraged from using these products through misquoted (or misinterpreted) data.
At least three of the links you provide are to the MSDS (Material Safety Data Sheet) for pyrethrins. These do not relate to the toxicity of a product, spray or shampoo in normal usage. Also, in most cases (unless otherwise stated) an MSDS refers to the active ingredient in its pure chemical form – not diluted in a shampoo etc.
All chemicals require a MSDS giving such information as physical/chemical properties, storage, handling, emergency disposal methods, accidental ingestion, toxicity, environmental fate etc. Even a little pot of Copper Sulphate arriving in a school chemistry lab will have had a MSDS enclosed with the packaging. Google for MSDS Acetic acid (vinegar) and Sodium Chloride – it may put you off having them on your chips!
Of course the chemicals sound toxic – rightly or wrongly the figures quoted are for LD50 . I’m still puzzled as to why pyrethrins are considered so harmful to guinea pigs. As Librarygryffon points out, the LD50s seem pretty high,
“LD50 Rat oral 1.2 g/kgâ€
How about comparing that with data for Ivermectin
LD50 Oral Rat 10 mg/kg ! (I gulped a bit when I read that).
Gorgeous Guineas products contain Neem. The MSDS for Neem (chemical name Azadirachtin) notes that this, too, produced sensitisation in guinea pig skin and the LD50s are very comparable with those of the pyrethrins.
http://www.ozonebiotech.com/msds/msds/MSDSAzadirachtinTechnical.pdf
In another link on the guinealynx page, the paper concludes …
“Summary
Pyrethrins are generally effective insectides that display low toxicity to mammals, breakdown quickly in the environment due to light or air interactions, and are rapidly metabolized.â€
I agree that amongst the literature you quote there are a couple of instances of severe anaphylactic reactions in human or guinea pig. Unfortunately that is life and somewhere in the world you will find someone with a very severe allergy to just about anything. It’s unrealistic, though, to suggest that people are placing themselves in mortal danger by bathing their pigs.
Anyway, you are of course entitled to your own opinions. I don’t want to endanger my animals and I have never felt that I was doing so by using these products. I have found them to be incredibly fast and efficient in relieving pigs’ distress from ‘passengers’.
Of course, if some people are so vehemently against them it is worth seriously looking into the reasons why …..which I now have done.
As yet, I don’t find the argument at all convincing.
I don’t personally feel that these links
alone provide the evidence and if your vet is warning people against using pyrethrins I am sure that he has information in addition to the links provided. Any chance of finding it please?