I imagine the first few times Humans encountered other species there where a few, biological problems. I mean, at least one person must have touched something without testing it first. -- Anon Guest
There is a general rule for space: never enter an untrusted area without your livesuit. The corollary, of course, is: don't trust anywhere. Even the cleansing booths have to be checked thoroughly for compatibility before you should try bathing in them.
Some species can't go near the solid form of salt. Some species can't abide theobromine. Some species are averse to light. Finding one definitive means of cleansing oneself is complicated at best and impossible at worse. There are species that bathe in fine dust. There are species whose lungs are shredded to a bloody pulp in fine dust. There are species for whom the mixture known commonly as soap is deathly toxic.
In space, there's a multitude of reasons to be careful in the shower.