Since the ZOE Health Study (formerly the ZOE COVID Study) app launched in March 2020, it has helped identify and confirm many important symptoms of COVID-19, including loss of smell (anosmia), skin rashes, and sudden confusion (delirium).
It has also uncovered what's commonly known as “COVID tongue,” changes to the mouth or tongue caused by COVID-19.
What do we know about COVID tongue?
In the ZOE Health Study app, we ask contributors to log any unusual symptoms they experience when they have COVID-19, as well as common symptoms like a sore throat, runny nose, and sneezing.
An increasing number of people were reporting that their tongue didn’t look normal, particularly that it was white and patchy.
Prof. Tim Spector, a co-founder of ZOE, helped raise awareness about this interesting symptom back in January 2021 by sharing a picture on his Twitter page.
He got a lot of responses, including some pictures, from people saying that they, too, had noticed changes to their mouth or tongue when they had COVID-19.
A review of studies from December 2020 also described these changes, supporting our observations.
The researchers found that having a dry mouth was the most common issue, followed by loss of taste (dysgeusia) and a fungal infection (oral thrush).
The team also described changes in tongue sensation, muscle pain while chewing, swelling in the mouth, and ulcers on the tongue or inner surface of the mouth and lips.
What causes COVID tongue?
It’s not clear what causes COVID tongue or other changes to the mouth, such as ulcers or swelling, during the illness.
It might be a direct effect of COVID-19, or it could be a more general immune-related response to being ill.
Another possibility is that people with COVID-19 may be more susceptible to fungal infections in their mouth (oral thrush), which show up as white blotches.
However, people who have had COVID tongue often report that treatment with antifungal drugs was unsuccessful.
How common is COVID tongue?
In September 2020, researchers in Spain published a paper reporting that around a quarter of people hospitalized with COVID-19 had changes to their mouth or tongue.
We don’t think COVID tongue is as common in mild cases of COVID-19. But we don’t yet know how common it is in the wider community.
Mouth ulcers are very common, and many illnesses and infections can cause changes to the surface of the tongue, such as an unexplained condition called geographic tongue that can last for months.
We also don’t know whether changes to the mouth or tongue can be the only symptom of COVID-19. Plus, it’s unclear whether these changes tend to happen earlier or later in the illness.
To find out more, we’re now asking about any new mouth ulcers or changes to the tongue as part of the symptom questions in the ZOE Health Study app.
If you’ve noticed any strange changes to your tongue or unusual ulcers — especially if you’re experiencing any other potential symptoms of COVID-19 — please download the app, log your symptoms, and take a COVID-19 test.
You should also self-isolate until you’re sure you don’t have the virus.
Stay safe and keep logging.