Researchers are learning more about this mysterious symptom of COVID-19. Here's a rundown of what they are, what might be causing them, and more.

Since the pandemic began, some unusual symptoms have been linked with COVID-19. One of the most surprising is so-called "COVID toes"—a red or purplish rash or raised bumps typically on the tips of the toes.

Experts have been unsure about whether COVID toes were actually linked to COVID-19 (or just some odd coincidence in some patients), and it hasn't made any official list of COVID symptoms. But now, new research has strengthened the connection.

Credit: AdobeStock

A small study, published on October 5 in the British Journal of Dermatology, analyzed 63 people with redness and swelling in their hands and toes, also known as chilblain-like lesions (after chilblains, a condition triggered by exposure to extreme cold temperatures). Fifty of those study participants had COVID toes, according to the researchers; all had tested positive for the virus. Thirteen of the study subjects were determined to have chilblains lesions.

The researchers found that both groups developed their symptoms as a result of an immune response containing high levels of certain auto-antibodies, especially an antibody called type I interferon. The endothelial cells, which make up the thin membrane that lines the inside of blood vessels, also seemed to play a role.

The language in the study is pretty medical jargon-y, but dermatologist Ife J. Rodney, MD, founding director of Eternal Dermatology Aesthetics and a professor at Howard University, breaks it down. "As with other viral infections, your body mounts an immune response in an attempt to fight off the COVID-19 virus," she tells Health. "This immune response causes inflammation throughout your body that can present in a variety of different ways on the skin." Interferon is a protein involved in inflammation, she adds.

COVID-Toe-Embed-GettyImages_ 1250715074
Credit: Getty Images

That can lead to rashes that may feature flat, red spots, and some may be itchy or even painful, Dr. Rodney says. "In COVID toes, the inflammation also damages small blood vessels in the toes, leading to a reddish-purple discoloration of your skin." That discoloration is usually seen in a condition called chilblains, she says. "We are unsure why the COVID rash takes on this specific presentation, as it does not seem to be more common in the wintertime or related to cold exposure," she adds.

Why some people who have COVID get COVID toes

It's not entirely clear, but "the reason why some people experience these symptoms more than others is likely because of differences in the degree to which one person's immune system reacts versus another person's," Joshua Zeichner, MD, director of Cosmetic & Clinical Research in Dermatology at Mount Sinai Hospital in New York City, tells Health.

Keep this in mind, though, per infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security in Maryland: "COVID toes are not a very common phenomenon, but do occur and should prompt medical evaluation."

When did doctors first start seeing COVID toes?

News of COVID toes first surfaced in an April 2020 press release shared by the General Council of Official Colleges of Podiatrists in Spain after podiatrists began "registering numerous cases of sick people, mainly children and young people, who had small dermatological lesions on their feet." Sometimes COVID toes appeared in the absence of other COVID-19 symptoms; sometimes they developed before the appearance of other symptoms.

These lesions, per the council, are "purple-colored" and typically pop up around the tips of the toes, though they usually heal without leaving marks on the skin. The council compared the marks to those that result from chickenpox, measles, and pernio (small lesions that appear after exposure to very cold temperatures).

Later that month, the International Federation of Podiatrists published a case study detailing similar findings, describing a 13-year-old boy who suddenly presented with lesions on both feet. Two days later, he presented with general COVID-19 symptoms—fever, muscle pain, and headaches—along with "intense itching and burning on the foot lesions." The boy was never tested for COVID-19, nor were any other family members, but his sister and mother showed symptoms of coronavirus before the boy's symptoms manifested. The boy's foot lesions began to clear up within a week, per the report.

The American Academy of Dermatology also has its own registry of dermatological issues where people can report skin-related symptoms possibly linked with COVID-19—including "COVID toes."

On the other hand, a small pair of studies called into question whether such lesions are symptom of the virus at all. A research team in Belgium, reporting in the June 25, 2020 issue of JAMA Dermatology, described 31 mostly teenage and young adult patients with purplish-red lesions on their toes and/or fingers. None tested positive for the SARS-CoV-2 virus, which causes COVID, and all were negative for antibodies to the virus.

Researchers suspect that these patients' skin symptoms may be due to community containment and lockdown measures imposed as a result of the pandemic. A majority (64%) reported decreased physical activity and more time spent in sedentary positions as they worked from home or were home schooled. Notably, most patients indicated that they remained barefoot or in socks most of the day.

Similarly, in the second study, researchers in Spain evaluated 20 children and teens who developed a purplish skin rash on their feet and/or hands. None had COVID-19 symptoms or evidence of infection based on nasal swab and blood testing. Also writing in the June 25, 2020 issue of JAMA Dermatology, the authors say one possibility is that the kids' symptoms may have been related to the quarantine experience of going barefoot or only wearing socks and engaging in little physical activity.

Why kids and young adults might be more at risk of COVID toes

Nazanin Saedi, MD, dermatologist at Thomas Jefferson University in Philadelphia, points out that "COVID toes" have mainly surfaced in children and young adults. "Children and young adults have stronger immune systems and they have a strong local response," she previously told Health.

Ted Lain, MD, board-certified dermatologist and chief medical officer at Sanova Dermatology, previously told Health that "the scientific community hypothesizes that 'COVID toes' are possibly a sign of a robust immune response, and also could be why younger people tend to have a more mild course of infection than adults."

What to do if you suspect you have COVID toes

If you happen to develop "COVID toes" but don't have any other symptoms of the virus, Dr. Rodney says you shouldn't automatically assume that you have COVID-19. Chilblains-like lesions can be seen with other conditions, she points out, so it's best to get tested for COVID-19 and take things from there.

If you do, in fact, have "COVID toes," Dr. Zeichner says you can expect that the rash will last for about two weeks, although it could be longer. "Less commonly, the rash has been reported to last for months, even after the initial COVID infection has resolved," he says.

As for taking care of your toes, Dr. Rodney recommends keeping them "warm and dry." Otherwise, you may need to simply wait until the discoloration goes away.

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 CDCWHO, and their local public health department as resources.

To get our top stories delivered to your inbox, sign up for the Healthy Living newsletter