By this point in the long slog of the pandemic, many people know the telltale symptoms of a COVID-19 infection: a ragged ache in your throat, a pernicious cough, congestion, fever and full-body exhaustion. But a tiny subset of people also develop less common symptoms, ones that can sound like hexes from a children’s story: hairy tongues, purple toes, welts that sprout on their faces.

“Every infectious disease has common and uncommon manifestations,” said Dr. Mark Mulligan, an infectious disease specialist at NYU Langone Health. And as we learn more about the coronavirus, he said, we may better understand the underlying causes behind these infrequent symptoms — but until then, it’s largely guesswork.

Confounding symptoms have been a component of COVID since the start of the pandemic; the loss of taste and smell has become a disturbing sign of the disease. COVID also has the potential to disrupt menstrual cycles, a side effect some women also reported after vaccination.

A study of more than 60,000 people who tested positive for COVID and reported their symptoms found that a small percentage experienced ringing in their ears, sore eyes, rashes, red welts on their faces or lips, hair loss and unusual joint pains. A larger analysis of more than 600,000 people in Britain showed that a fraction of those with COVID also developed purple sores and blisters on their feet and numbness across their bodies, among other maladies.

Doctors aren’t sure why only some people develop these unusual symptoms. Genetics might play a role, Mulligan said; vaccination status could also have something to do with it, as an unvaccinated person might have a more severe infection, which could generate a different course of symptoms. Scientists have also found that the coronavirus can enter the bloodstream in a minority of people, he said, which means that it’s possible that the virus could enter various organs across the body and cause symptoms beyond the respiratory system.

Antiviral treatments like Paxlovid may potentially alleviate symptoms like a COVID-related rash, perhaps because they can reduce the amount of virus in your blood, said Dr. Kelly Gebo, an infectious disease specialist at Johns Hopkins Medicine. But it’s unclear whether these symptoms are directly caused by the virus or by the body’s response to it.

Inflammation could also be a culprit, said Dr. Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco. If the virus gets into the bloodstream and affects multiple parts of the body, immune cells flock to those areas, Chin-Hong said. That means an ear, for example, which the virus would typically not affect, may become inflamed, not function as well and potentially ache.

COVID also leaves patients in a weakened state, he said, which means pathogens lingering around their bodies from previous infections — like herpes or the virus that causes shingles — can reactivate, causing rashes or cold sores in the wake of COVID.

A third theory is that the stress that can come with a COVID infection — the anxiety of quarantine, the loss of income, the fear of long-term health implications — can also trigger symptoms like hair loss and hives, Chin-Hong said.

Each of these symptoms, when associated with COVID, typically resolves in a matter of weeks, often without treatment, he added. And there aren’t set rules for how doctors treat them, said Gebo. “We have definitive guidelines on how to treat shortness of breath,” she said, “but we don’t have definitive guidelines on these.”

Here’s what else we know about the causes of — and potential treatments for — some of these symptoms.

HAIRY TONGUE

Healthy tongue cells rapidly replace themselves, Chin-Hong said, but if older cells linger and build on top of one another, it forms a dark, thick, fuzzy overgrowth, often called hairy tongue. Even before COVID, doctors saw patients with hairy tongue related to viral infections, smoking, antibiotic use and poor hygiene, he said, adding, “It’s more common than people think.”

“I know it looks really scary to people,” he said, but the affliction is generally temporary. Some people may also feel a burning sensation inside their mouths. Those with this symptom shouldn’t be “freaked out,” Chin-Hong said. People with hairy tongue can use a tongue scraper or toothbrush to scratch away those tongue cells, and they can make sure to practice good oral hygiene to prevent additional buildup.

In rare cases, people with COVID may also develop thrush, otherwise known as oral candidiasis, which occurs when a fungus infects your mouth. It has been linked to a suppressed immune system or the use of antibiotics, Chin-Hong said. Doctors typically diagnose thrush by examining the white lesions that can sprout on your cheek, tongue or mouth; the treatment is usually 10 to 14 days of an antifungal medication.

TINGLING NERVES

When people develop the sensation of pins and needles on their skin, it may be because their nerves are inflamed by immune cells as they fight off infection, Chin-Hong said. It’s also possible that the virus itself could damage peripheral nerves, like those that go to your hands and feet, Gebo said; this also occurs with the shingles infection.

“What we don’t know is what’s a direct impact of the virus itself or what’s inflammation,” she said. “These are things we’re trying to figure out.”

Researchers at Washington University in St. Louis found that people who tested positive for COVID were roughly three times as likely to report pain, tingling and numbness in their hands and feet than those with negative tests.

For many people, that tingling sensation goes away in a matter of days, Gebo said. If patients are in pain, she added, they should consult their doctors, who may recommend taking Tylenol or Motrin.

People with persistent nerve pain, even after they recover from the virus, should consult their doctors, said Dr. Marc Sala, co-director of the Northwestern Medicine Comprehensive COVID-19 Center.

RASHES

It’s well-established that viruses can induce rashes, Sala said, and he noted that he has seen a wide variety of skin afflictions in patients with COVID. The American Academy of Dermatology Association cites itchy bumps, chickenpoxlike blisters, rashes that form lacy patterns on the skin and raised bumps as potential skin conditions linked to COVID. If you develop a rash that lingers after you recover from COVID, Sala recommends consulting a dermatologist.

HAIR LOSS

Any type of physical or emotional distress can cause your hair to fall out, said Dr. Shilpi Khetarpal, a dermatologist at Cleveland Clinic. It’s not totally clear whether an infection with COVID itself or the stress related to it leads some people to experience hair loss, she said. If you find yourself among those who lose some hair during or after a COVID infection, don’t panic, she said, adding, “It’s not scarring; it comes back. It just needs time.”

COVID TOE

Scientists are still conflicted about what causes “COVID toe,” the frostbitelike rash and blisters that form on some people’s feet and fingers after they become infected, causing toes and the tips of fingers to become swollen and purple. One theory is that people with COVID may experience microvascular clots, which occur in the smallest blood vessels in your body and block the blood supply, causing that discoloration, Sala said.

Patients who develop COVID toe usually do so during the acute phase of an infection, he added, and the symptoms tend to resolve soon after. The American Academy of Dermatology Association recommends using a hydrocortisone cream to treat it. Like most rare COVID symptoms, as unnerving as it might be, the swelling typically resolves on its own — for reasons doctors aren’t entirely sure of.

“We’re still learning about COVID,” Mulligan said. “We don’t understand everything.”

This article originally appeared in The New York Times.

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