I just realized that my last post might be hard to understand without a science background, I apologize. LD50 is an experimental value that causes death in 50% of the exposed population. Toxicologists use this value to gain a relative understanding about how toxic a certain chemical species is. An LD50 of 2690 mg/kg is extremely high. This means that for a 1kg, or 1000 g animal, they would have to orally ingest 2690 mg of permethrin to induce death in 50% of exposed animals. This is a lot of pesticide. There is no possible way the snake could have been exposed to this amount. You would have to of literally poured it down the snakes throat. Additionally, the dermal LD50 is greater than 2000 mg/kg, meaning that it is not considerably permeable through the skin and does not cause noticeable toxicity when exposed in that manner.

As for the mechanism of action, pyrethroids act by binding to and affecting voltage gated sodium channels. Essentially this prolongs the time that neurons fire, inducing neurological changes. It is not considered to be a general irritant, and only a moderate eye irritant (which most everything is).

Point is, don't freak out. These chemicals are not acutely hurting your snake. Federal regulatory bodies, which are known for being extremely conservative when it comes to chemical regulations, do not require that respiratory or skin safety precautions be taken with this chemical.

In the world of pesticides it is a weakling. Hope this gives you some peace of mind.