Just found this thread
I actually had to call Scent Lok and ask the question for quadro because I'd never heard of the permethrin and yes, have never had issues with chiggers and ticks up here. Ticks out west, yes but not here yet for me anyway. I have had fellow hunters say they have had ticks here in Michigan, but I haven't.
The pro staff and tech guy at Scent Lok said they have been asked about permethrin quite a bit and said it degrades the glue which is used to bond the 2 fabrics that sandwich the activated carbon liner. As the glue degrades the carbon doesn't stay in its place and then there becomes areas with no carbon coverage and also some carbon will escape.
Sorry, that's all I got and obviously the Thermocell is worthless on ticks and chiggers.