I have also heard of a cream or topping that does the opposite. When applied directly to the anus it quickly builds to a burning or stinging sensation that is eased with the clenching of the anus. I heard about it from a male Dom during a social event. He said that it is used when he fucks his male and female subs. It forces them to clench giving him a tighter, better feeling on his cock but also makes them focus on clenching which forces them to loses pleasure. I'll look into it further to find the name of this cream and post back here with the information.