Light

Yes.

The main effect of "skunking" (light-struck) is caused by some wavelenths of light causing reactions with the hop compounds that are present in the beer. These wavelengths occur naturally in sunlight (strongest) and also are present in florescent lights (to a lesser degree than sunlight). Most feel that there isn't enough of those wavelengths in incandescent light to bother the beer much. There's lots of details available on this subject if you google for it

Also, light colored beers get skunked easier and quicker than darker beers, probably because the light can penetrate further into it and strike more hop compounds.

So... sitting your light colored beer in the sunlight is a very bad idea. Don't keep it under florescent light for LONG periods either. Many/most folks do their brewing WORK under florescent lights and that doesn't seem to harm it noticably. But storage under florescent light will skunk it - like in stores who use coolers with built-in florescent bulbs.

So.... your dark bathroom is fine - and especially fine if it has a incandescent bulbs. Or, hey, throw a black trash bag over it! RDWHAHB