THURSDAY, June 25, 2020 (HealthDay News) -- Two new studies strongly suggest that the so-called "COVID toe" lesions that have popped up among some Americans during the pandemic may not be caused by infection with the new coronavirus after all.
Despite intensive testing over a wide time period, none of the 51 study patients afflicted with the reddened, tender toes came up positive for SARS-CoV-2, the virus that causes COVID-19.
Instead, the simple fact that many people are spending weeks on end walking around barefoot at home might be the cause, the researchers suggested.
The Spanish researchers behind one of the studies now theorize that "these skin lesions are not induced by the virus, but by the quarantine state itself."
The team, led by Dr. Ignacio Torres-Navarro, a dermatologist with the University Hospital of la Fe Polytechnic in Valencia, conducted an in-depth analysis of COVID toes in 20 children. Ruling out infection as a cause, they said the condition "appeared mainly in children isolated in houses that were not well suited for individuals who spent long periods barefoot or only wearing socks and with very little physical activity."
Another study, this time led by researchers in Belgium, conducted a similar study into purplish-red chilblain-like lesions on the feet (29 patients) and hands (three patients) of individuals seen at a Brussels dermatology clinic in April. Most were teens or young adults.
Again, COVID-19 was suspected as a cause, but highly accurate testing -- done via blood or nasal swabs over a long period of time -- found zero evidence of SARS-CoV-2 infection in any of the patients.
The Belgian team agreed with the Spanish researchers that the quarantine lifestyle may be what's driving a rise in COVID toes and chilblains in the young.
"All patients reported that they had either been working from home or were home schooled" since lockdown was instituted in Belgium in early March, said a team led by dermatologist Dr. Anne Herman, of the Catholic University of Louvain. Most admitted to a largely "couch potato" lifestyle during that time, and "most patients declared that they remained barefoot or in socks during that time."
There was one other risk factor: Most were relatively skinny, "suggesting that thin people may be more at risk of developing chilblains," Herman's group said.
Dr. Michele Green is a dermatologist at Lenox Hill Hospital in New York City. Reading over the studies, she agreed that "with so many of these patients presenting with COVID toe and testing negative to the virus, it may not be directly related to the virus." But she added that "further studies are needed to understand the cause and relationship."
According to the Mayo Clinic, risk factors for foot lesions such as chilblains include being underweight, exposing skin to cold or damp conditions, and weather that's both cool and humid. Women are more prone to chilblains than men. Covering up exposed skin and keeping your house warm can cut the risk, the Mayo experts said.
The two new studies were published online June 25 in JAMA Dermatology.