I've heard that DEET will chew through...
I've heard that DEET will chew through Goretex. Does this have any effect if exposed to any kind of garments?
100% Pure Deet will eat through most fabrics and lost of other things too. There are very few 100% deet products available. Even the most potent are rarely more than 15%.
This product is for the application to clothing and not skin, so I would say that it would be fine to try on you outerwear.
Permethrin is 100% safe on gear. I spray my whole tent and backpack to push the bugs back even further and so they stay out of my tent.