By now we know that a COVID-19 infection can affect you in some unexpected ways. In addition to a fever or cough, some people might develop “COVID nails,” which can appear as deep lines on your fingernails. But those signs aren’t always related to COVID-19—and not everyone who has the infection will develop them.
“Do your nails look odd? COVID nails are increasingly being recognized as the nails recover after infection and the growth recovers leaving a clear line. Can occur without skin rashes and appears harmless,” Tim Spector, professor of genetic epidemiology at King’s College London, wrote on Twitter earlier this month. The tweet drew a lot of new attention to COVID nails, but simply having what looks like COVID nails isn’t necessarily a cause for concern.
COVID nails appear to actually be a manifestation of a condition called Beau’s lines, which can appear after illnesses that cause fever. There have been a few case studies highlighting Beau’s lines after COVID-19 infections, including this study involving a 45-year-old man in the Canadian Medical Association Journal. Other case studies, such as this one about a 60-year-old woman published in the Journal of the European Academy of Dermatology and Venereology, have also found people who developed red half-moons in their nails alongside COVID-19 infections.
In all these cases, it’s not clear whether COVID-19 specifically caused the nail issues, and experts are still trying to understand how common they are. For one review study, the authors identified six case studies looking at nail changes in people who’d had COVID-19. Of those people, two presented with Beau’s lines, two had red half-moons, and two had other issues.
The truth is that a lot of health issues—big and small—can affect your nails. For instance, if you see lines that run vertically on the nail, those are common and generally harmless, the American Academy of Dermatology (AAD) explains. But Beau’s lines, which appear as deep lines or grooves that run across the width of your nails, can occur when your nails suddenly stop growing or grow more slowly than usual.
That can happen when you develop a fever, undergo chemotherapy, injure the nail, or experience a period of major stress, the AAD says. Beau’s lines can be a result of viral illnesses that come with a high fever (such as COVID-19), but they can also be caused by uncontrolled diabetes or a zinc deficiency, the Mayo Clinic says. In general, you don’t need to worry too much about this condition, but if you notice this and can’t point to an obvious cause, the AAD recommends talking to your doctor or dermatologist to figure it out.
And if you notice a discoloration in the half-moon area of your nail, that can be a sign of many conditions, such as lupus, arthritis, or alopecia areata, the AAD says. Again, this change in the color of your half-moons on its own doesn’t automatically mean you have an underlying condition. But it’s a good idea to check in with a doctor if you notice a sudden unexplained change, especially if you’re also experiencing other symptoms.
So, if you do get COVID-19, you might also notice these harmless, temporary nail changes. And if you notice what looks like COVID nails and you have other common symptoms of COVID-19, you should get in contact with a health care provider and consider getting a coronavirus test. But simply having a few odd lines on your nails doesn’t mean you have the infection.