The (More or Less) Complete Guide to AD&D Hygiene covers such vital topics as how often characters use the restroom, how paladins can stay clean, when characters should visit the dentist, and how clerics can help keep the area free of humanoid waste. Even a mage has to do laundry.
The item has a fairly complex publication history, with an initial major version released in 1993 and revised in 1994 (but still called the 1993 version). The 1994 revision is the most widely circulated and was converted into DOC format in 2000. A major revision of the Text version also occurred in 1996, greatly expanding the topics covered.
P.S. How often do characters have to use the restroom? Their CON score with a multiplier applied in hours apart. And it varies by sex.