Warning: Graphic images in this story may disturb some readers.
A New York woman who underwent a trendy 'fish pedicure' had her toenails split in half months later.
The unnamed woman, in her 20s, dipped her feet in a tub of warm water teeming with doctor fish, according to a case report in journal JAMA Dermatology.
"In their natural habitat, suction assists them in sticking to rocks while they ingest plankton," author Shari Lipner wrote in the report. "Being omnivores, when there are insufficient plant sources, they will eat human skin."
Six months later she went to the doctor, saying while her toenails didn't hurt, they looked weird - the top half was separate to the bottom half.
It turns out she'd developed a condition called onychomadesis, in which the nail separates from the bed below, preventing its proper growth.
With no history of toenail problems in her family or other causes, doctors say it must have been the fish pedicure that started it - perhaps one of the tiny fish nibbled on a spot it shouldn't have.
"We are not entirely sure of the mechanism of action but most likely it's from the trauma of the fish on the nail matrix, which is the nail growth centre, that probably caused this condition," dermatologist Shari Lipner told NBC news show Today.
It's believed to be the first case of a fish pedicure leading to onychomadesis.
While studies have shown the treatment can be good for treating psoriasis, the trendy procedure has been banned in a number of US states. Doctor fish only nibble on dead human skin when they're starved, as animal rights activist such as PETA have pointed out.