A lead investigator on the ZOE COVID-19 symptom study in the UK has suggested that if your nails look odd, it could be a sign that you have previously been infected with COVID-19.
You may have noticed that on visits to the doctor, physicians will occasionally check your nails. They aren't just checking for manicures, but for signs of illness that can be seen there. Beau’s lines are horizontal ridges that go across your whole nails. While they can be caused by picking at the nails or infections around the fingertips, they can also be a sign of serious illness, especially if they are seen across multiple nails.
There are a number of illnesses that can interrupt your nail growth, from kidney failure to pneumonia. Most come with other noticeable symptoms, which people will likely notice long before they see the effect in their nails.
Principal Investigator Tim Spector suggests that the same kind of lines can be seen in some people following COVID-19 infection.
The Beau's lines have not been added as an official symptom of COVID-19, though there are case studies that lend support to the idea that they could indicate a previous infection.
In one, published in the Canadian Medical Association Journal, a 45-year old man showed doctors horizontal grooves on his finger and toenails. "The grooves were most noticeable over his great toenails bilaterally," according to the report. "Three and a half months previously, he had been given a diagnosis of coronavirus disease 2019 (COVID-19) after a positive nasopharangeal swab polymerase chain reaction test, owing to symptoms of diarrhea, fever and shortness of breath, which lasted for 10 days and did not require admission to hospital."
The rate of nail growth meant that the researchers could narrow down when the ridge occurred. "As the toenails grow at a rate of about 1.62 mm per month, the distance of the Beau's lines from the proximal nailfold in our patient reflects the timing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection," they wrote.
As Spector points out, having these ridges can be signs of many other infections or due to other causes, including hypertension, epilepsy, eczema, severe malnutrition, and chemotherapy, so it can't be used alone to determine if you have had COVID-19.
Moreover, the subject will need to be studied a lot further before conclusions are drawn. The lines themselves are harmless and resolve when the cause itself is resolved, though they may take several months to fully grow out.
Should you develop Beau's lines, or should they reoccur, it may be worth discussing with a physician or health care provider, in case they're a symptom of underlying or unknown conditions.
For more information about COVID-19, check out the IFLScience COVID-19 hub where you can follow the current state of the pandemic, the progress of vaccine development, and further insights into the disease.