What Causes COVID Toes?

COVID toes
Image Credit: Chris Curry / Shutterstock

A study has shown that a combination of antiviral proteins and autoantibodies result in the chilblain-like lesions that characterize COVID toes.

Along with respiratory symptoms, the novel coronavirus is also responsible for various cutaneous manifestations. Early in the pandemic, doctors began reporting patients with a strange rash on their toes. The rash would start with painful blisters, often full of pus, and lead to the toes turning red or purple. For some, the rash caused extreme soreness and itch, while for others it was painless. These chilblain-like lesions (CLL) soon became known as ‘COVID toes’. As their frequency continues to increase, doctors are left wondering what could be triggering the lesions. 

Now, a recent study in the journal British Association of Dermatologists, sheds new light on the link between COVID-19 and the strange rash.

The team of researchers examined 50 patients at Saint-Louis Hospital in France, from April 9-16, 2020. All had presented to the hospital with CLL. The researchers also recruited a control group consisting of patients with similar chilblains lesions not linked to COVID. They looked at both results from blood and skin tests for both groups of patients.

What are Chilblain-like Lesions (CLL)?

Chilblains lesions are inflammatory papules, mainly involving the fingers and toes. Although most cases are idiopathic, some are triggered by the cold. Connective tissues diseases such as lupus erythematosus are also linked to the condition. Moreover, it is one of the most reported cutaneous manifestations of COVID-19.

SARS-CoV-2 infection strongly triggers the expression of type I interferon (IFN)-stimulated genes, which assist in the host’s antiviral protection.

study authors

The results of the study showed an increased expression of type I interferon (IFN)-stimulated genes in patients with COVID related CLL. Although type I IFN helps protect from viral infections, it results in endothelial damage infiltration of inflammatory cytotoxic proteins. Moreover, the study also reported an increase in autoantibodies in these patients. These antibodies end up attacking the body’s own cells, calling inflammation and destroying small blood vessels.

Doctors believe that the study’s results will help develop effective treatments for patients affected by the condition.


Cassius, C. et al. (2021). Type I interferon response and vascular alteration in chilblain-like lesions during the COVID-19 outbreak. British Journal of Dermatology. doi: https://doi.org/10.1111/bjd.20707https://onlinelibrary.wiley.com/doi/full/10.1111/bjd.20707


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