(NEXSTAR) — Nearly two years into the global pandemic, we’re still learning about COVID’s rarer symptoms. Among them is a condition called “COVID tongue,” which affects an unknown number of people who get the coronavirus.

The effects of COVID tongue vary from person to person, according to the U.K.’s ZOE Covid Study, which tracks the occurrence of dozens of coronavirus symptoms. Some people report more minor versions, like having a dry mouth. Others notice white patches on their tongues, or they notice swelling and/or ulcers.

There are also cases of people developing a “geographic tongue” following a COVID infection. Geographic is an inflammatory condition, according to the Mayo Clinic, and it’s harmless – though it could be uncomfortable. The tongue becomes inflamed, creating small bumps, patches and red islands, giving it a “maplike, or geographic, appearance.”

There are several theories on what might cause COVID-related tongue issues, according to Healthline. It could be oral thrush, a fungal infection in your mouth, that’s a side effect of some COVID medications. Your body’s immune response to COVID could also be causing inflammation everywhere, including your tongue. The virus may also be hitting your salivary glands, says Healthline, which could be causing them to produce less saliva and give you that feeling of dry mouth.

How prevalent COVID tongue is with omicron remains to be seen. It seems to be relatively rare overall, but there hasn’t been a recent scientific study published. It was not among the 20 most commonly reported omicron symptoms, according to the ZOE Covid Study. The most common symptoms appear to be runny nose, headache, fatigue, sneezing and sore throat.

A study published out of Spain in September 2020 found 11% of hospitalized COVID patients had tongue issues, but it was a small sample size and only looked at patients in one field hospital.

As with many COVID symptoms, more research is needed to fully understand COVID tongue and how to treat it. If you think you have COVID-related tongue inflammation or other pain/discomfort in your mouth, contact your doctor for treatment options. Swelling can be especially dangerous, and you should call 911 if you’re having trouble breathing, according to Healthline.