With the price of rubber lens hoods being so low, why would you want to subject yourself and equiptment to chemical fumes. You will probably spend more to treat them than to just buy a new one every 10-20 years. My cheapest hood finally tore after 25 years, I think I paid five or six bucks for it back then. I just looked at my 20+ year old Tiffen hoods, and they are still in great shape.

Sounds like a case of tripping over dollars to pick up a nickel.