Specifically skin?
I just had the most wonderful idea for a gift.
Some time ago I read about some kind of ooze, little creatures that can be taken as wizard familiars. They live in the sewers of some big city in golarion, if I remember right.
Perhaps they are what you are looking for. I don't remember the name but if I find something I'll add it.
Got it:
Torbles are a variety of weird, gelatinous vermin that dwell in the sewers of Westcrown. Local wizards sometimes take them as familiars.Also known as "chordoplasms" by scholars or "ooze bugs" by common folk, torbles are a hybrid of ooze and insect. As hybrids, they are vulnerable to tactics or strategies that combat either oozes or vermin.
The whole article can be found here.