What Are 'COVID Nails'—And Are They a Sign You've Had the Virus?

COVID-19 may cause many complications after recovery, from a persistent cough to "brain fog," per the Centers for Disease Control and Prevention (CDC). Another possible, though not dangerous, side effect to keep on your radar: COVID nails, aka Beau's lines. As of July 2022, it wasn't observed frequently, but it could happen.

In May 2021, Tim Spector, a British epidemiologist and principal investigator of the Zoe COVID Symptom Study app, tweeted about the phenomenon and included a photo of COVID nails, writing, "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."

Plenty of people in the comments section asked about COVID nails, what they look like, and if they're something to worry about. Here's what you need to know about COVID nails.

What Are COVID Nails, Exactly?

There's actually a medical term for this—Beau's lines. "When you have major physiological stress, like an illness, you basically have a shifting in the nail cycle," New York City dermatologist Doris Day, MD, told Health. You'll usually see this in all of your nails (not just one nail) and maybe even in your toenails.

A January 2022 review of studies about COVID-19 impacts on hair and nails published in the Journal of Cosmetic Dermatology found three documented cases of Beau's lines after COVID-19. In those three cases, the nails were affected after one month, two months, or a little over three months after COVID-19.

Outside of the three cases of Beau's lines, seven people in the studies reviewed experienced other nail changes, each of a different type.

What Do COVID Nails Look Like?

Beau's lines are grooves that run horizontally across your nail plate, per an August 2021 paper published in the journal Skin Appendage Disorders. COVID nails/Beau's lines can look like ridges, grooves, or indentations, according to Dr. Day. The lines go away on their own as nails continue to grow out, per the August 2021 paper.

Have you had COVID-19 but don't see COVID nails? This won't necessarily happen to everyone, and it's more apparent in some people than others. "Some people don't see it in the nail because it's not so obvious," Dr. Day said.

Does Having COVID Nails Mean You Had COVID-19?

Not necessarily—many illnesses can cause this, infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, told Health.

"It has been well known that any kind of systemic disease can disrupt nail growth which can be reflected in abnormalities in the appearance of nails," Dr. Adalja said. "This can be seen with any critical illness."

The flu, an infection, and pretty much anything that causes a high fever can also cause these grooves. Even chemo can cause Beau's lines. "Having it after chemotherapy is a classic case," Dr. Day said.

As a whole, Beau's lines are usually "nothing to worry about," Dr. Day said, adding, "it just shows that your body went through something, and you're done with it."

Joshua Zeichner, MD, director of cosmetic and clinical research at the Icahn School of Medicine at Mount Sinai in New York City, told Health: "The good news is that even without treatment, it should correct itself. Once the nail change has happened, it is not permanent, so it is just a waiting game for the nail to grow out."

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.