Researchers believe they have uncovered the reason some people who suffer from COVID go on to develop chilblain-like lesions on their toes.
Known as 'COVID toe', the skin condition may be a side effect of the immune system overreacting in its response to fighting off the virus, a new study has suggested.
The symptom sees chilblain-like inflammation and redness on the hands and feet, with the results sometimes lasting for months.
Scientists now believe the findings, published in the British Journal of Dermatology, could help with treatments to ease the symptoms.
Watch: Are ‘COVID toes' a symptom of coronavirus?
While COVID toe can develop at any age, researchers said it is more commonly seen in children and teenagers.
For some it is painless, but for others, the rash can be extremely sore and itchy, with tender blisters and swelling.
For the study, a team of researchers from University of Paris, France analysed 50 people with suspected COVID toe in the spring of 2020, and 13 others with similar chilblains lesions that were not linked to COVID infections, because they occurred long before the pandemic began.
Scientists say the results have shed more light on this side effect associated with COVID, helping to pinpoint why such a condition occurs. Turns out it is all to do with the immune system of our bodies.
It seems the toe and finger lesions are caused by the body going into 'attack' mode, to counter the COVID infection.
Two components of our immune system lead to formation of these lesions, both involving mechanisms the body uses to fight coronavirus.
One is an antiviral protein called type 1 interferon, and the other is a type of antibody that mistakenly attacks the person's own cells and tissues, not just the invading virus.
It was also revealed that cells lining blood vessels, which supply the affected areas, appeared to play a critical role in the development of COVID toes and chilblains.
Researchers hope their findings will help patients and doctors to better understand the condition.
"The epidemiology and clinical features of chilblain-like lesions have been extensively studied and published, however, little is known about the pathophysiology involved," Dr Charles Cassius, the senior author of the study, told The Telegraph.
"Our study provides new insights."
While the skin lesions caused by COVID toes do typically go away on their own, some people may need treatment with creams and other drugs
Watch: The Coronavirus Might Cause a Rash In Some People, Here's What You Should Know