June 25 (UPI) -- "COVID toes" might not be a symptom of coronavirus infection, but instead the result of lifestyle changes during lockdown, two small studies published Thursday by JAMA Dermatology found.
"COVID toes" has been described as "purplish-red lesions on the feet," according to the researchers involved in the studies.
The "symptom" mirrors that of a condition called Chilblains, or perniosis, a painful inflammation of the small blood vessels in the skin that occurs after repeated exposure to cold air, they said.
The phenomenon has become a trending topic on social media and earlier research has suggested the lesions are associated with asymptomatic or mild COVID-19, although findings to date have been inconclusive, the researchers said.
Biopsies performed on all participants in the two studies suggest they may have developed Chilblains, while separate antibody testing revealed they were negative for the new coronavirus, SARS-CoV-2, the researchers on both studies reported.
In a related commentary also published Thursday by the same journal, researchers who were not involved in the two studies said that with extensive testing failing to identify other risk factors, it appears that "COVID toes" is perniosis.
"Both author groups propose that lifestyle changes imposed by the quarantine, such as walking barefoot in unheated homes, inactivity and time spent in sedentary positions, could explain these findings," the commentary authors, who were not part of either study, added.
In the first study, which enrolled 31 teenagers and young adults in Belgium with lesions on their toes and feet, researchers confirmed a diagnosis of chilblains in 22 via skin biopsy.
However, in all 31 patients, SARS-CoV-2 RNA remained undetectable in nasal and throat swabs and in biopsy samples of the skin lesions, the researchers said.
In addition, antibody testing was also negative for the virus in all of the patients, they said.
In the second study, which enrolled 20 children age 18 and younger, biopsy findings appeared to be Chilblains, but antibody test results for all were negative for antibodies to SARS-CoV-2, the researchers said.
It's also possible that study participants were seen early in the course of COVID-19, or they were asymptomatic or had extremely mild cases of the disease, they said.
"We are not stating [definitively that] the lesions are not caused by the virus, [just] that we could not detect it," co-author Dr. Ignacio Torres-Navarro, a dermatologist at University Hospital in Valencia, Spain, told UPI.
"The relationship between skin disease and COVID-19 has yet to be proven," he said. "If the virus is implicated, maybe individuals [with the lesions] do not represent a serious risk for contagion or for severe disease."