According to a new report in the journal JAMA Dermatology, the patient had received such a treatment and noticed later that her toenails began shedding.
When a young USA woman began losing her toenails, her doctors were baffled.
For one, the fish are often used on more than one person, making the risk of transmitting infections a real possibility.
Months after her nails stopped growing and fell off, the woman went to visit her dermatologist, who ruled out other known causes of onychomadesis, including major illness or side effects from medications.
Lipner is unaware of any other such cases linked to fish spas, whose popularity seem to have drawn from unfounded claims about their health benefits, according to her report.
Fish pedicures involve putting your feet in a tub of water filled with tiny fish called Garra rufa, which eat dead human skin.
Writing in the journal JAMA Dermatology, she explained that the freakish beauty ritual first gained traction after people noticed that wild populations of the toothless fish - a member of the carp family native to Turkey - liked to nibble on human skin, and for whatever reason, preferred munching on unsightly psoriasis plaques more than normal tissue. And although there's no way to test for fish-pedicure-induced toenail loss, she told CNN, "I think we're fairly sure that it was the fish pedicure". Onychomadesis only temporarily stops nail growth, which usually resumes within 12 weeks, according to a 2017 study of the condition.
The case, as far as Lipner knows, would be the first documented instance of onychomadesis ever caused by fish.
As for the woman, her nails will likely return, but not for a long time. Lipner was not able to identify the fish species involved in this case. Dr. Lipner continued that her patient's case could be the first incident where onychomadesis occurred due to a fish pedicure.
The report doesn't specify where the woman had her pedicure, for the sake of protecting her anonymity, but it's worth noting that the pedicures have been banned in many states in the U.S., but they remain popular in China. "It was a bit of a craze people got excited about, and then they moved on to the next thing", said Verner-Jeffreys, who added that the concern surrounding fish spas is not just about human health.
In the United Kingdom, an investigation was conducted by the UK's Fish Health Inspectorate discovered bacteria outbreak among the fish used in these spas.
Their use has been banned in some states in the USA - at least 10, by Lipner's count. "Therefore, we will have to wait quite a while to see the outcome", she said.