This i gotta hear. Savage, how had you heard it was used? To get rid of puffy nips or just to irritate them into looking hard? Over the years I've heard some of the damnedest "cures" for slight gyno.
Preparation H does sound a bit weird, but the cream shrinks hemroid tissue...i have heard it works with other tissue as well. actually, i've heard some strippers spackle the stuff on to suck everything in. lol.
Thats a better explanation then I was expecting. I assumed it was another case of an irritant which caused the nip to harden, like the bros using iceyhot LOL. Your theory is more toward actual reversal of the condition though I don't know how similar heroid and fat glands are, but its certainly worth investigating. Hopefully some of our more chem/medically oriented bros will weigh in.