Long COVID can affect the mouth in several different ways. Some people develop dry mouth, recurrent mouth ulcers, burning sensations, changes in taste, a sore tongue or repeated cold sores. These symptoms do not usually have a single cause. Instead, researchers think they may result from several overlapping biological processes, including autonomic dysfunction, small fibre neuropathy, immune dysregulation, mast cell activation, viral reactivation and, in some people, autoimmune conditions such as Sjögren’s syndrome. Understanding which mechanism is most likely can help explain why symptoms vary so much from one person to another.
Last update July 2026
Key Takeaways
- Long COVID can affect the mouth as well as the lungs, heart and nervous system.
- Dry mouth is one of the most commonly reported oral symptoms.
- Some people develop recurrent mouth ulcers or cold sores after COVID.
- Taste and smell changes may persist for months or even years.
- Burning mouth syndrome, tongue pain and altered saliva production are also reported.
- Oral symptoms may reflect autonomic dysfunction, immune dysregulation, viral persistence or autoimmune disease.
- Persistent symptoms should always be assessed because nutritional deficiencies and other medical conditions may also contribute.
“”My Mouth Just Doesn’t Feel Normal Anymore”
Most people think of Long COVID as a condition affecting the lungs, heart or brain. Few expect it to change something as ordinary as their mouth.
Yet many people notice exactly that.
Food suddenly tastes strange. Their mouth feels dry no matter how much they drink. Toothpaste starts to sting. Spicy foods become unbearable. Mouth ulcers appear more often than they ever did before. Cold sores return after years of being quiet. Some people describe a burning tongue, while others feel as though their mouth has become unusually sensitive or numb.
At first these symptoms can seem completely unrelated. In reality, they all rely on the same systems: healthy nerves, a well-regulated immune system, adequate saliva production and normal blood flow. Long COVID can affect each of these, which helps explain why mouth symptoms are surprisingly common yet so different from person to person.
Why Can Long COVID Affect the Mouth?
Every time you eat, swallow, speak or smile, dozens of different systems work together without you ever noticing. Healthy nerves, saliva, immune cells and tiny blood vessels all play a part. Long COVID has the potential to affect several of these systems at once, which helps explain why mouth symptoms can vary so much from one person to another.
Why Does My Mouth Feel So Dry?
Dry mouth is one of the most common mouth symptoms people report after COVID, but it’s also one of the easiest to dismiss. Friends and family often say, “You’re probably just dehydrated.” Drinking more water is sensible, but if you’ve ever carried a water bottle everywhere and still felt like your mouth was full of cotton wool, you’ll know it isn’t always that simple.
Making saliva is actually a surprisingly complicated process. It’s controlled by the autonomic nervous system—the same automatic network that regulates your heart rate, blood pressure, sweating and digestion. When that system isn’t working properly, as it often isn’t in Long COVID, saliva production can also become disrupted.
That may leave you with a mouth that feels dry even though you’re drinking normally. Some people wake up feeling as though they’ve slept with their mouth open, while others find dry foods become difficult to swallow or they need to sip water constantly during conversations. Over time, reduced saliva can also increase the risk of tooth decay, bad breath and oral infections because saliva does far more than simply keep the mouth wet.
Dry mouth isn’t always caused by autonomic dysfunction. Some medications reduce saliva production, and persistent dryness particularly alongside dry eyes may suggest an underlying condition such as Sjögren’s syndrome. That’s why persistent symptoms deserve assessment rather than simply being blamed on Long COVID.
Why Does My Mouth Burn When Nothing Looks Wrong?
One of the most frustrating symptoms is a mouth that burns, tingles or feels as though you’ve just sipped a cup of tea that’s far too hot even though there are no ulcers, no infection and nothing obvious to see.
When most people hear the words nerve damage, they think about numb feet or tingling hands. Few realise the smallest nerve fibres are found throughout the body, including the tongue, lips and lining of the mouth. These tiny nerves help detect pain, temperature and touch, so when they stop working normally, the mouth itself can feel abnormal.
Researchers think small fibre neuropathy (SFN) may explain some of these symptoms in Long COVID. If these nerves become irritated or damaged, they can send abnormal signals to the brain, causing burning, tingling, numbness or unusual sensitivity even though the mouth appears completely healthy.
Small fibre neuropathy is unlikely to explain every case of burning mouth, but it highlights an important point: sometimes the problem isn’t the tissues you can see it’s the nerves underneath them.
Why Do Mouth Ulcers Keep Coming Back?
The inside of your mouth heals remarkably quickly. Every meal, every brush of your teeth and every accidental bite on your cheek creates tiny injuries that usually disappear before you even notice them.
That repair process depends on a well-balanced immune system. If immune function becomes disrupted, healing may become less efficient and inflammation can linger for longer than it should. Researchers think this may be one reason some people develop recurrent mouth ulcers after COVID.
At the same time, it’s important not to assume every mouth ulcer is caused by Long COVID. Iron deficiency, vitamin B12 deficiency, folate deficiency, coeliac disease, inflammatory bowel disease and several autoimmune conditions can all cause recurrent ulcers. That’s why persistent or unusually frequent ulcers deserve proper assessment rather than simply being put down to Long COVID.
It’s also important to remember that mouth ulcers and cold sores are different conditions. Mouth ulcers are usually linked to inflammation or immune changes, whereas cold sores are caused by reactivation of the herpes simplex virus (HSV).
If recurrent mouth ulcers are your main concern, read our article “Why Do I Suddenly Keep Getting Mouth Ulcers After COVID?”( coming soon) If you’re experiencing repeated cold sores or other viral infections, “Viral Reactivation in Long COVID: Why EBV, Herpes and Shingles Can Return” explains why dormant viruses may become active again after COVID.
Why Has Food Started Burning My Mouth?
Some people notice that foods they have eaten all their lives suddenly become difficult to tolerate after COVID. A mild curry now feels painfully hot. Toothpaste stings. Mint burns. Even acidic foods such as tomatoes or orange juice can leave the mouth feeling raw.
Sometimes this happens because the tissues inside the mouth have become more sensitive. In other people, there may be no visible inflammation at all.
Researchers are still trying to understand why. One possibility is mast cell activation, where immune cells called mast cells release chemicals such as histamine more easily than they should. These chemicals help protect us against infections and allergens, but they can also make nerves much more sensitive. As a result, sensations that once felt normal may suddenly feel irritating, painful or overwhelming.
Another possibility is that the nerves themselves have become more sensitive, particularly if small fibre neuropathy is also present. For some people, both mechanisms may be contributing at the same time.
This doesn’t necessarily mean you have Mast Cell Activation Syndrome (MCAS), and not everyone with Long COVID experiences these symptoms. But it may help explain why your mouth suddenly reacts to foods, drinks or even toothpaste that never caused problems before.
Why Doesn’t Food Taste the Same Anymore?
Losing your sense of taste during COVID became one of the best-known symptoms of the pandemic. What has surprised researchers is how many people continue to notice changes months or even years later.
For some, food tastes bland. Others describe a constant metallic taste, while favourite foods suddenly become unpleasant. Coffee, chocolate, onions or red wine are common examples. Some people even say they no longer enjoy eating because everything tastes “wrong.”
Taste is much more complicated than most of us realise. It depends not only on the taste buds on your tongue but also on your sense of smell, healthy nerves and normal communication between the mouth and the brain. If any part of that system is disrupted, the flavours you experience can change.
Researchers think several mechanisms may be involved. Damage to the smell pathways during the initial infection is one explanation, but ongoing nerve dysfunction, persistent inflammation and changes within the nervous system may also contribute. In other words, it’s not always the tongue that’s changed—it’s how your brain is receiving and interpreting those signals.
For many people, taste gradually improves with time, but recovery can be slow and unpredictable. Some notice steady improvement over months, while others experience periods where symptoms seem to improve before changing again.
Could COVID Have Unmasked Another Condition?
Long COVID isn’t always the whole story.
For some people, COVID appears to act like a stress test for the immune system. Instead of causing a completely new disease, it may uncover a condition that had been quietly developing for months or even years without obvious symptoms.
One example is Sjögren’s syndrome, an autoimmune disease in which the immune system attacks the glands that produce tears and saliva. Many people think of Sjögren’s as simply “dry eyes and dry mouth,” but it can also cause profound fatigue, joint pain, mouth ulcers and nerve problems.
That doesn’t mean everyone with a dry mouth after COVID has Sjögren’s. In fact, most don’t. Dry mouth is much more commonly caused by autonomic dysfunction, medications or the effects of Long COVID itself.
The important message is not to dismiss persistent symptoms. If your dry mouth is severe, is accompanied by dry eyes, frequent dental problems, recurrent mouth ulcers or other autoimmune symptoms, your GP may consider blood tests or referral to a specialist. Sometimes the answer is Long COVID. Sometimes COVID has simply been the event that brought another condition to light.
Could More Than One Thing Be Happening at the Same Time?
Probably.
One of the biggest lessons researchers have learned about Long COVID is that it rarely follows a simple rule of one symptom, one cause.
Someone with a dry mouth may also have burning sensations. Another person might develop recurrent mouth ulcers and cold sores. Others notice changes in taste alongside tingling of the tongue or increased sensitivity to certain foods. These symptoms don’t necessarily point towards a single explanation.
For example, autonomic dysfunction may reduce saliva production, leaving the mouth dry and more vulnerable to irritation. At the same time, immune dysregulation could make mouth ulcers more likely, while small fibre neuropathy increases pain or burning sensations. If mast cells are also involved, foods or toothpaste that never caused problems before may suddenly become uncomfortable.
This overlap helps explain why two people can both say, “COVID changed my mouth,” yet have completely different experiences.
It also explains why there probably isn’t going to be one treatment that works for everyone. The future of Long COVID care is likely to involve identifying which biological processes are driving symptoms in each individual, rather than assuming everyone has the same underlying problem.
The Bigger Picture
If you’ve noticed changes in your mouth since COVID, you’re not imagining them.
For a long time, mouth symptoms received very little attention because they seemed minor compared with breathlessness, heart problems or neurological symptoms. Yet the mouth depends on many of the same systems that Long COVID is known to affect. Healthy nerves, a balanced immune system, good blood flow, normal saliva production and intact smell and taste pathways all have to work together every day without us noticing.
When one or more of those systems is disrupted, the mouth can change in ways that seem completely unrelated. Dryness, burning, altered taste, mouth ulcers, cold sores or increased sensitivity may look like separate problems, but in some people they may simply reflect different parts of the same underlying illness.
The challenge is that these symptoms are not unique to Long COVID. Nutritional deficiencies, medications, allergies, infections and autoimmune diseases can all produce similar problems. That’s why new or persistent mouth symptoms deserve proper assessment rather than being automatically blamed on Long COVID.
Researchers are only beginning to understand why COVID affects the mouth in some people but not others. As with many aspects of Long COVID, there is unlikely to be one single explanation. Instead, different biological mechanisms may overlap, with each person having their own combination of autonomic dysfunction, nerve involvement, immune dysregulation, viral reactivation or other contributing factors.
Understanding those differences is one of the keys to developing more personalised treatments in the future.
requently Asked Questions
Can Long COVID damage my teeth?
Not directly, but it can increase the risk of dental problems. A persistently dry mouth reduces the protective effects of saliva, making tooth decay, gum disease and oral infections more likely. Looking after your oral hygiene and seeing your dentist regularly becomes even more important if dry mouth is an ongoing problem.
Why does my mouth feel dry even when I’m drinking plenty of water?
Dry mouth isn’t always caused by dehydration. In Long COVID, changes in the autonomic nervous system, certain medications, salivary gland dysfunction and autoimmune conditions can all reduce saliva production. Drinking water may help temporarily, but it won’t always address the underlying cause.
Why does toothpaste suddenly burn after COVID?
Some people find that mint, strong flavours or even mild toothpaste suddenly become uncomfortable after COVID. Researchers think this may reflect increased nerve sensitivity, immune changes or, in some people, mast cell activation. If symptoms persist, switching to a milder toothpaste and discussing the problem with your dentist or GP may help.
Is burning mouth syndrome part of Long COVID?
Some people with Long COVID report burning, tingling or stinging sensations in the mouth despite little or no visible abnormality. Researchers are investigating whether small fibre neuropathy, autonomic dysfunction or immune changes may contribute, but there is unlikely to be a single explanation for everyone.
Can Long COVID affect my tongue?
Yes. Some people notice a sore tongue, burning sensations, tingling, altered taste or increased sensitivity. These symptoms may be related to nerve dysfunction, dry mouth, inflammation or changes in the way the nervous system processes sensory information.
When should I see my GP or dentist?
You should seek medical advice if you have mouth ulcers lasting longer than three weeks, severe dry mouth, repeated oral infections, difficulty swallowing, white or red patches that don’t heal, or any symptom that is persistent, worsening or difficult to explain. Although Long COVID may contribute, these symptoms can also have other treatable causes.
Medical Disclaimer
This article is for educational purposes only and should not be used as a substitute for professional medical advice, diagnosis or treatment. Although Long COVID can affect the mouth in a variety of ways, symptoms such as dry mouth, mouth ulcers, burning mouth, altered taste or difficulty swallowing may also be caused by nutritional deficiencies, medications, infections, allergies, neurological disorders or autoimmune diseases. If your symptoms are severe, persistent, worsening, or associated with unexplained weight loss, persistent ulcers, bleeding, difficulty swallowing or other concerning features, seek assessment from your GP, dentist or an appropriate healthcare professional.
References
- Davis HE, McCorkell L, Vogel JM, Topol EJ. Long COVID: major findings, mechanisms and recommendations. Nature Reviews Microbiology. 2023.
- Nalbandian A, Sehgal K, Gupta A, et al. Post-acute COVID-19 syndrome. Nature Medicine. 2021.
- World Health Organization. Post COVID-19 condition (Long COVID).
- NICE. COVID-19 rapid guideline: Managing the long-term effects of COVID-19 (NG188).
- Dziedzic A, Wojtyczka R. The impact of coronavirus infectious disease 19 (COVID-19) on oral health. Oral Diseases. 2021.
- Favia G, Tempesta A, Barile G, et al. COVID-19 symptomatic patients with oral lesions: clinical and histopathological study on 123 cases of the University Hospital Policlinic of Bari. International Journal of Medical Sciences. 2021.
- Iranmanesh B, Khalili M, Amiri R, et al. Oral manifestations of COVID-19 disease: A review article.Dermatologic Therapy. 2021.
- Son K, Jamil R, Chowdhury A, et al. Oral manifestations and oral health-related quality of life in patients with COVID-19 and post-COVID conditions: A systematic review. Journal of Oral Pathology & Medicine. 2024.
- Broccolo F, et al. SARS-CoV-2 infection and reactivation of latent viruses. Pathogens. 2021.
- Oaklander AL, Mills AJ, Kelley M, et al. Peripheral Neuropathy Evaluations of Patients With Prolonged Long COVID. Neurology: Neuroimmunology & Neuroinflammation. 2022.
Suggested Articles
Why Is My Mouth So Dry After COVID? (future article)
Why Do I Suddenly Keep Getting Mouth Ulcers After COVID? (coming soon)
Viral Reactivation in Long COVID: Why EBV, Herpes and Shingles Can Return (coming soon)
Why Do I Feel Like I Have Glandular Fever Again After COVID?
Small Fibre Neuropathy in Long COVID (coming soon)
Immune Dysregulation in Long COVID
T-Cell Exhaustion in Long COVID
Why Do Foods Suddenly Burn My Mouth After COVID? (coming soon)
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