After a young woman’s toenails started to separate from her toes, a doctor finally zeroed in on the reason: a fish pedicure, according to a report published recently in the journal JAMA Dermatology.

Six months prior, the woman had dunked her feet in a tub of water filled with tiny fish called Garra rufa that will eat dead human skin when no plankton are around. It wasn’t until later on that she noticed her nails beginning to shed.