The skin condition known as Covid toe may be a side-effect of the immune system’s response to fighting off the virus, according to a recent study.

Covid toe, which develops within a week to four weeks of catching the virus and sometimes lasts for months, can result in inflammation and redness on the hands and feet. It is most common in children and teenagers and can involve the toes and fingers becoming swollen and changing colour.

The study, from researchers in Paris and published on Tuesday October 5 in the British Journal of Dermatology, looked at 50 participants with suspected Covid toe and 13 with similar chilblains lesions that arose before the pandemic.

They found both conditions were caused by the body generating high levels of certain antibodies, which mistakenly target a person’s own cells and tissues as well as the virus. They also found higher levels of type 1 interferon, a key protein in the antiviral response.

‘The confirmation of the cause will help to develop new treatments to manage it more effectively,’ podiatrist Dr Ivan Bristow told the BBC. The lesions go away on their own for most, but some may need treatment with creams and other drugs, he added.

The relationship between Covid-19 and chilblain-like lesions remains ‘controversial’, the researchers wrote. However, they cited evidence showing a link between peaks of the occurrence of the lesions and Covid-19 deaths in 2020 and a recurrence of previous chilblain lesions during Covid.

Although the condition can affect anyone who catches the virus, Covid toe reportedly most commonly affects children and teenagers.