COVID-19 can cause a surprisingly wide range of mouth sores, from painful ulcers on the tongue and inner cheeks to blisters, red patches, and swollen gums. These oral lesions develop because the virus targets cells lining the mouth, and they can appear before, during, or even weeks after the respiratory symptoms most people associate with the disease. Managing them usually involves a combination of good oral hygiene, medicated rinses, and pain relief, though the specifics depend on whether the sore is caused directly by the virus, by an opportunistic infection piggybacking on a weakened immune system, or by the medications used to treat COVID itself.
Why the Mouth Is a Target
SARS-CoV-2 gets into human cells by latching onto a receptor called ACE2. That receptor is found throughout the body, but the tongue and salivary glands have an especially high concentration of it. Once the virus binds to ACE2 on the surface of oral cells, a series of molecular events allows it to fuse with the cell membrane and release its genetic material inside, hijacking the cell’s machinery to replicate.
1Frontiers in Cellular Neuroscience. The oral manifestations and related mechanisms of COVID-19 caused by SARS-CoV-2 infection This abundance of ACE2 in the mouth also helps explain why so many COVID patients lose their sense of taste early in the illness.2PubMed Central. Oral lesions in patients with SARS-CoV-2 infection: could the oral cavity be a target organ?
Beyond direct viral invasion, the immune system’s inflammatory response plays a role. COVID-19 triggers elevated levels of inflammatory signaling molecules throughout the body, and that inflammatory storm can disrupt the normal balance of tissues in the mouth, delaying healing and making the lining of the oral cavity more vulnerable to breakdown.3PubMed Central. Covid-19 and oral diseases: Crosstalk, synergy or association? So the sores are not just about the virus sitting in oral tissue; they also reflect collateral damage from the body’s own defense response.
What COVID Mouth Sores Actually Look Like
There is no single “COVID mouth sore.” The oral manifestations reported in the literature span a long list: ulcers, erosions, blisters, pustules, red or white patches, depapillated or fissured tongue, swelling, spontaneous bleeding, and even tissue death in severe cases.4PubMed Central. Oral manifestations of COVID-19 disease: A review article The most commonly described pattern involves aphthous-like ulcers, the round, shallow, painful sores that look a lot like everyday canker sores but tend to show up alongside other COVID symptoms.5PubMed Central. Oral aphthous ulcers associated with COVID-19
The tongue takes a particular beating. Reports of “COVID tongue,” characterized by a swollen, discolored tongue with patchy loss of the tiny bumps (papillae) that normally cover its surface, became a recognizable phenomenon during the pandemic. Some patients developed geographic tongue, where smooth red patches appear surrounded by white borders, giving the tongue a map-like appearance. In other cases, a white or yellowish coating suggested fungal overgrowth rather than direct viral damage.
These lesions commonly appear alongside loss of taste or smell. One review of the literature found that ulcers, blisters, necrotizing gingivitis, white and red plaques, and taste changes were the most frequently reported oral findings, with the lesions often emerging at the same time as olfactory and gustatory symptoms.3PubMed Central. Covid-19 and oral diseases: Crosstalk, synergy or association?
When They Show Up
The timing of oral lesions varies widely from person to person. A systematic review tracking the timeline found that about half of reported cases developed mouth sores simultaneously with or within a week of their other COVID symptoms. In a small fraction of cases, the oral lesions were actually the first sign of infection, appearing before cough, fever, or fatigue. On the other end of the spectrum, some patients did not develop mouth problems until two to three weeks after their initial symptoms, and a few cases appeared only after hospital discharge.6PLOS ONE. Oro-facial mucocutaneous manifestations of Coronavirus Disease-2019 (COVID-19): A systematic review
In people with mild or even asymptomatic COVID, oral lesions occasionally emerged a full month after the initial diagnosis. Once they appeared, most resolved within five days to two weeks, though some patients were left with persistent changes like depapillation of the tongue, geographic tongue, or ongoing taste disturbances even after the sores themselves healed.6PLOS ONE. Oro-facial mucocutaneous manifestations of Coronavirus Disease-2019 (COVID-19): A systematic review
Herpes Flare-Ups and Oral Thrush
Not every mouth sore during a COVID infection is caused by the coronavirus itself. The immune suppression and inflammation that accompany COVID can give other pathogens an opening. Herpes simplex virus (HSV), which lies dormant in the nerve tissue of most adults who carry it, is one of the most common opportunistic offenders. In a cross-sectional study of 80 COVID-positive patients, about 35% experienced one or more HSV reactivations during their illness. Roughly 43% of those patients reported that the herpes flare-up was more severe than any previous episode they could recall, and about 36% had their very first symptomatic HSV outbreak during their COVID infection.7PubMed Central. COVID-19 and Herpes Simplex Virus Infection: A Cross-Sectional Study Research has also linked both COVID infection and COVID vaccination to broader herpesvirus reactivation, including varicella-zoster (the virus behind shingles).8PubMed Central. COVID-19 infection and vaccines: potential triggers of Herpesviridae reactivation
Oral candidiasis, commonly known as thrush, is another frequent secondary infection in COVID patients. The white patches of thrush appear when Candida yeast, normally kept in check by the immune system, proliferates on the tongue and inner cheeks. Research has found that the immune suppression seen in COVID patients, combined with poor oral hygiene during illness and the use of corticosteroids and antibiotics in treatment, creates favorable conditions for Candida overgrowth.9PubMed Central. Oral Candidiasis in Adult and Pediatric Patients with COVID-19 This matters for management because thrush requires antifungal treatment, not just the general wound care that works for viral ulcers.
Is It the Virus or the Treatment?
One of the trickier aspects of COVID mouth sores is figuring out their actual cause. Several studies have concluded that a meaningful share of oral lesions in hospitalized COVID patients result not from the virus itself but from external factors: co-infections, the mechanical trauma of ventilation equipment, the medications used during treatment, or preexisting conditions that worsen during illness.10PubMed Central. The Oral Lesion in the COVID-19 Patient: Is It True Oral Manifestation or Not?
Corticosteroids like dexamethasone, widely used to manage severe COVID inflammation, suppress the immune system and create the conditions for both thrush and HSV reactivation. Broad-spectrum antibiotics prescribed to prevent or treat bacterial superinfection can disrupt the oral microbiome, again inviting Candida. Intubation tubes can cause mechanical ulcers and dry out the mouth. Even prolonged oxygen therapy via nasal cannula can crack and chap the lips. For patients recovering at home from milder illness, the simple fact of being too sick to brush and floss normally can shift the bacterial balance in the mouth enough to cause gum inflammation or ulceration.
The practical takeaway is that if you develop mouth sores during or after a COVID infection, the treatment depends on the underlying cause. A viral ulcer, a herpes flare-up, and a thrush infection look different and require different approaches, so getting a proper evaluation from a dentist or doctor is worth the effort.
Mouth Problems in Children With COVID
Children can develop oral symptoms during COVID, particularly in the context of multisystem inflammatory syndrome in children (MIS-C), a serious post-infection condition where widespread inflammation affects multiple organs. In a review of 47 pediatric MIS-C patients, nearly half had red or swollen lips, while about 11% developed “strawberry tongue,” a distinctive bright-red, bumpy appearance. These oral findings tracked closely with other signs of systemic inflammation: children who had mouth or throat changes were also more likely to have a skin rash and conjunctivitis.11PubMed Central. Oral manifestations of COVID-2019-related multisystem inflammatory syndrome in children: a review of 47 pediatric patients
A systematic review covering MIS-C and its overlap with Kawasaki disease found a consistent pattern of red mucous membranes, oral ulcers, dry and cracked lips, and strawberry tongue in affected children.12PubMed Central. Oral manifestations of multisystemic inflammatory syndrome in children (MIS-C) and Kawasaki disease associated to COVID-19: A systematic review These oral signs in a child who has recently had COVID should prompt urgent medical attention, since MIS-C can rapidly become serious and requires hospital-based treatment with immunoglobulins and anti-inflammatory drugs.
When Mouth Symptoms Persist After Recovery
For some people, the oral problems do not resolve when the acute infection does. In a survey-based study of long COVID patients, about 69% reported at least one oral condition linked to their infection, and roughly 47% said their oral symptoms had lasted longer than three months. The most commonly reported lingering issues were changes in taste or smell, dry mouth, and mouth sores, followed by oral thrush, recurrent ulcers, gum infections, and jaw joint dysfunction.13British Dental Journal. Oral manifestations of long COVID and the views of healthcare professionals
Burning mouth syndrome, a condition characterized by a persistent burning or tingling sensation in the mouth without visible sores, has also been linked to both acute and post-acute COVID. A systematic review found that COVID-related burning mouth syndrome can appear during the initial infection and persist as a chronic condition well into the recovery phase.14PubMed Central. COVID-19-Related Burning Eye Syndrome and Burning Mouth Syndrome: A Systematic Review and Meta-analysis Persistent dry mouth (xerostomia) compounds the problem, since saliva normally protects against oral infections and helps with tissue repair. If your mouth has been uncomfortably dry for weeks after COVID, a saliva substitute or a discussion with your dentist about stimulating saliva flow may help more than waiting it out.
The Periodontitis Connection
One of the more striking findings to emerge from COVID oral health research is the relationship between preexisting gum disease and COVID outcomes. Periodontitis, the chronic infection and inflammation of the gums and bone supporting the teeth, appears to make COVID worse. A study using multivariate models to adjust for confounders like age, sex, smoking, and other health conditions found that patients with periodontitis had roughly 3.7 times the odds of COVID health complications, about 3.5 times the odds of ICU admission, and over 4.5 times the odds of needing mechanical ventilation compared to patients with healthy gums or mild gum disease.15PubMed Central. Oral Lesions Associated with COVID-19 and the Participation of the Buccal Cavity as a Key Player for Establishment of Immunity against SARS-CoV-2
The likely explanation is that periodontitis keeps the body in a state of chronic low-grade inflammation, which primes the immune system to overreact when challenged by a second inflammatory trigger like COVID. The inflamed, ulcerated gum tissue may also provide an easier entry point for the virus. While this does not mean that treating gum disease will prevent severe COVID, it adds to a long list of reasons to take periodontal health seriously, particularly for people at higher risk of complications from respiratory infections.
Managing COVID Mouth Sores at Home
Most COVID-related oral lesions in non-hospitalized patients are self-limiting, meaning they will resolve on their own as the infection clears. That said, they can be quite painful, and a few strategies can speed healing and reduce discomfort:
- Gentle oral hygiene: Keep brushing twice daily with a soft-bristled brush, even if your mouth is sore. Skipping oral care invites secondary infections that make things worse.
- Saltwater rinses: A teaspoon of salt in a cup of warm water, swished for 30 seconds a few times a day, can soothe irritation and reduce bacterial load.
- Medicated mouth rinses: In one case report, a patient with persistent COVID-related tongue lesions used a prescribed mouth rinse protocol for about a month and experienced roughly 90% improvement in both the sores and tongue sensitivity.16PubMed Central. Conservative treatment with mouthwashes followed by tongue photo biomodulation therapy in Covid-19: a case report Your dentist or doctor can recommend a rinse appropriate to your situation, whether antiseptic, anti-inflammatory, or antifungal.
- Over-the-counter pain relief: Topical benzocaine gels or oral analgesic rinses can numb painful sores temporarily. Systemic pain relievers like acetaminophen or ibuprofen help with overall discomfort.
- Hydration: Staying well hydrated supports saliva production, and saliva is your mouth’s natural defense system. Sip water throughout the day, especially if you are experiencing dry mouth as a symptom.
- Avoid irritants: Spicy, acidic, and very hot foods will aggravate open sores. Stick to bland, soft foods until the lesions heal.
If white patches appear on your tongue or inner cheeks, suspect thrush and see a healthcare provider. Antifungal medications, typically nystatin rinse or fluconazole tablets, are needed to clear a Candida infection. Similarly, if you recognize the clustered blisters of a herpes outbreak, antiviral medication like valacyclovir can shorten the episode and reduce severity.
Mouthwash and Viral Load
Early in the pandemic, researchers explored whether antiseptic mouthwashes could reduce the amount of live virus in the mouth and potentially lower transmission risk. The results have been mixed. A meta-analysis found that povidone-iodine (PVP-I) mouthwash at a 1% concentration was effective at temporarily reducing SARS-CoV-2 viral load in saliva, while cetylpyridinium chloride (CPC) and chlorhexidine (CHX) did not show a statistically meaningful effect.17PubMed Central. Effectiveness of mouthwashes on reducing SARS-CoV-2 viral load in oral cavity: a systematic review and meta-analysis A separate systematic review agreed that PVP-I showed promise but noted that any viral load reduction appeared to be short-lived, largely fading within 30 minutes of rinsing.18PubMed Central. Efficacy of mouthwash on reducing salivary SARS-CoV-2 viral load and clinical symptoms: a systematic review and meta-analysis
A randomized controlled pilot study testing CHX, hydrogen peroxide, and CPC rinses in hospitalized patients found no significant difference over a control group in reducing viral load at two- and three-hour time points. The researchers noted that all groups, including the control, showed some reduction in viral load at those intervals, suggesting the mechanical act of rinsing and spitting may account for much of the effect.19Scientific Reports. Efficacy of three antimicrobial mouthwashes in reducing SARS-CoV-2 viral load in the saliva of hospitalized patients: a randomized controlled pilot study The upshot is that while mouthwash will not cure COVID or reliably prevent transmission, PVP-I-based rinses may offer a brief window of reduced oral viral load, and routine rinsing supports general oral health during illness. Do not use PVP-I if you have thyroid conditions or iodine allergies without checking with your doctor first.
Changes in Saliva During COVID
COVID does not just cause visible sores; it changes the composition of saliva itself. A study comparing saliva from COVID patients and healthy controls found that 30 proteins differed significantly in abundance between the two groups, with 20 of those proteins at lower levels in infected patients. Enzyme activity in saliva shifted as well: total esterase activity dropped substantially in COVID patients, while the activity of another enzyme (gamma-glutamyl transferase) rose sharply, pointing to an altered biochemical environment in the mouth during infection.20Nature. Saliva changes in composition associated to COVID-19: a preliminary study
These compositional shifts may help explain why the mouth becomes more vulnerable to secondary infections during COVID, since many of the proteins that dropped in abundance play roles in immune defense and tissue maintenance. They may also contribute to the metallic or altered taste many patients describe. The research is still preliminary, but it adds another layer to the picture: COVID does not just damage oral tissue directly; it reshapes the chemical environment those tissues depend on for protection and repair.