The manifestations of the coronavirus are proving endless, and researchers are still working to uncover their underlying causes. There is growing evidence that rashes are a key feature of the disease, present in around nine percent of the Covid Symptoms study app users. One skin condition that emerged in the initial stages of the pandemic has now been identified as a side effect of the body’s immune response to the virus. Covid toes, the scientists noted, are less prevalent following vaccination.
Researchers at the Saint-Louis Hospital Paris believe inflammation of the toes may be a side effect by the body generating an immune response.
Published in the British Journal of Dermatology, a new study examined a sample of 50 participants with Covid toes.
A further 13 participants with chilblain lesions – that arose before the pandemic started – were also examined.
While drawing similarities between the two conditions, the team identified one mechanism in both groups that prompted an immune response with high levels of auto-antibodies.
These auto-antibodies – one of the key characteristics of auto-immune conditions – mistakenly attack the body’s own cells and tissues while inhibiting the virus.
The researchers noted that the key protein involved in the antiviral response in both groups was the type I interferon.
In addition to this immune response, the cells lining the blood vessels supplying the feet also appeared to play a vital role in the development of Covid toes.
The senior author of the study, doctor Charles Cassius, said the research provided a deeper understanding of the condition.
He explained: “The epidemiology and clinical features of chilblain-like lesions have been extensively studied and published, however, little is known about the pathophysiology involved.”
Chilblains are small itchy red patches that typically appear on the fingers and toes after hours of exposure to the cold.
They can disappear by themselves over the course of two to three weeks, but the NHS recommends being a GP if symptoms persist.
Covid toes, on the other hand, typically develop within a week to four weeks of being infected and can result in the toes and fingers becoming swollen and red.
The first reports of Covid toes emerged on April 29th, after researchers in Spain published a study that highlighted “cutaneous manifestations” of COVID-19 disease.
The report detailed five different rashes identified among 375 COVID-19 patients.
Key characteristics included itchy or painful chilblain-lied lesions on the hands and feet.
Other rashes identified during the study included small blisters on the torso, small red bumps, red or blue-looking, and raised areas of the skin, which were likened to nettle rash.
Later reports in May, published in the European Journal of Paediatric Dermatology, described an “epidemic” of Covid toe cases among youngsters in Italy.
The report stated: “We observed an ‘epidemic’ of acute and self-healing vasculitic lesions of the hands and feet in asymptotic children and adolescents.
“These lesions constituted a novelty that led us to establish a link with the other much more severe novelty, ie COVID-19, which also occurred almost simultaneously.”
Dermatologists have reported that instances of the side effect after vaccination remain rare.