the oxylormaphanifrofuckingwhatevertheyare ones are bad b/c they increase the melancytes which are what produce the melanin.
the problem is that when newly created melancytes show up, they are far more succesptible to uva radiation - which means that they are more likely to hit by that shit and mutate and turn into a little cancer generator (cancer being an uncontrolled cell that is replicating in a manner that doesn't do what its original intent was or even worse it is doing negative things - as in attacking other cells).
so while yes, they do work like a motherfucker, they have their extreme downsides and that is why it is very hard to get a script for them.
also - it acts on all cells, it is not seletive, so it also gets into the corenal tissue, which when exposed to uva radiation... I think it is protein degredation or something - but the end result is you get cataracts and can't see unless you get a cornea repleacement or removal... I hear those are unpleasant.