There are a few places in the world, mostly in Asia, that use Doctor Fish to help treat dermatological disorders like Psoriasis. The fish eat affected and dead areas of the skin leaving the healthy parts alone. More recently a few spas started touting this service as a means to clean dead skin from your body.
Andrew Bunney of Gimme 5 recently visited the Fish Reflexology Spa on Sentosa Island off the southern coast of Singapore and got to experience hundreds of tiny fish nibbling the dead skin off his feet. He comments, "the sensation feels somewhere between tickling and short electric shocks, and as time goes on, the shocks become harder. By the end your feet will be very smooth and relaxed." It's a truly symbiotic relationship.