Can COVID Cause Lip Sores? The Connection Explained

COVID-19 can cause lip sores through several distinct pathways, ranging from direct viral damage to the oral tissue to triggering dormant infections like cold sores. An Egyptian study of hospitalized COVID patients found that roughly nine out of ten developed some form of oral lesion, with the lips being one of the most commonly affected sites. The connection is real, but the type of lip sore matters: different mechanisms produce different lesions, and knowing which one you’re dealing with changes how you treat it.

Why the Mouth and Lips Are Vulnerable

SARS-CoV-2 enters human cells by latching onto a receptor called ACE2, and the cells lining your mouth happen to be rich in it. Research analyzing oral tissue found that ACE2 is present across the lips, tongue, and inner cheeks, with particularly high levels in the tongue’s surface cells. One study showed that over 93% of the ACE2-positive cells detected in oral tissue belonged to epithelial cells, the very cells that form the surface layer of your lips and mouth lining.¹ A separate analysis confirmed that ACE2 protein levels were especially high in lip and tongue tissue, particularly in the deeper basal layer of the epithelium.¹

This abundance of ACE2 receptors means SARS-CoV-2 can directly infect oral mucosal cells, and the virus has been shown to replicate in salivary gland cells, causing local inflammation.² That local infection and the immune response it triggers set the stage for the various sores, ulcers, and inflammatory changes that COVID patients report on their lips.

Oral Ulcers Directly Caused by the Infection

The most commonly reported lip and mouth lesions in COVID patients are ulcers. In one study of 124 COVID-positive patients in Egypt, oral manifestations appeared in about 90% of them, and ulcers specifically accounted for the vast majority of those lesions. The lips, tongue, and inner lip lining were the most common sites affected.³ These ulcers can look a lot like ordinary canker sores: round or oval, shallow, painful, and surrounded by a ring of redness. Some appeared as larger, irregular lesions with more tissue damage.

An interesting complication is that some of these ulcers look like herpes but aren’t. Researchers observed oral ulcers with a “herpetiform pattern,” meaning they resembled the clustered small blisters typical of a herpes outbreak, yet testing for herpes simplex virus came back negative.⁴ This is worth knowing because it means a cluster of small sores on your lip during a COVID infection doesn’t automatically mean you have herpes. The virus itself can produce look-alike lesions.

When COVID Reactivates Cold Sores

That said, COVID genuinely does trigger cold sore outbreaks in people who already carry the herpes simplex virus, and most adults do carry it. The mechanism involves several factors stacking up at once: the fever, the psychological stress of being sick, and the immune disruption that SARS-CoV-2 causes all create conditions that let dormant herpes simplex virus wake up. A cross-sectional study found a possible association between COVID-19 infection and both primary herpes infections and reactivation of latent ones, pointing to the virus’s direct effects on nerve tissue alongside the immune upheaval as likely drivers.⁵

A broader literature review reinforced this link, noting that herpes reactivation has been documented frequently enough during COVID-19 that some researchers have suggested these herpes flare-ups could serve as a warning sign of the severity of the underlying COVID infection.⁶ In other words, if you get a cold sore outbreak during COVID, it doesn’t necessarily mean your COVID is worse, but clinicians have noticed the two tend to track together.

The practical difference matters. A cold sore reactivated by COVID is still a herpes infection and responds to antiviral medications like acyclovir or valacyclovir. A COVID-caused ulcer that merely looks like herpes won’t respond to those drugs. If you develop lip sores during a COVID infection and they don’t respond to your usual cold sore treatment, that’s a clue the lesion may be directly virus-related rather than a herpes flare-up.

Erythema Multiforme and Lip Crusting

A less common but more dramatic type of lip involvement during COVID is erythema multiforme, an immune-mediated reaction that produces painful mouth ulcers and characteristic crusty, swollen lips. In one reported case, a 30-year-old woman showed up at an oral medicine clinic with extensive ulcers inside her mouth and crusted lesions on her lips along with target-shaped skin lesions on her body. She was diagnosed with erythema multiforme major, and it was only five days after being seen that she tested positive for COVID-19, meaning the oral and lip lesions had appeared before anyone realized COVID was the trigger.⁷

Erythema multiforme in this context is an overreaction of the immune system, not direct damage from the virus. The body’s inflammatory response to SARS-CoV-2 can go into overdrive and attack the mucosal surfaces and skin. Additional cases of oral erythema multiforme presenting with lip, mouth, and skin lesions in COVID patients have been documented, and these typically require steroid treatment rather than antivirals.⁸ The crusted, bleeding lips and widespread mouth sores look alarming, but erythema multiforme generally resolves once the underlying trigger is addressed and the inflammation is brought under control.

Cheilitis in Children

Lip inflammation, specifically cheilitis, has shown up as one of the early signs of COVID in young children, sometimes before other COVID symptoms become obvious. A case report described a 13-month-old boy who presented with persistent fever and cheilitis, with cracked, red, swollen lips, as his initial findings of COVID-19. This was before the medical community had even formally classified multisystem inflammatory syndrome in children (MIS-C).⁹

A systematic review of oral manifestations in MIS-C and Kawasaki-like disease triggered by COVID confirmed that swollen, dry, cracked lips were among the hallmark oral features, along with strawberry tongue, reddened mucous membranes, and oral ulcers.¹⁰ If your child develops cracked, peeling lips with a fever and no clear explanation like dehydration or windburn, it’s worth considering COVID or MIS-C as a possibility, especially if other symptoms like conjunctivitis or rash appear alongside.

Fungal Infections and the Disrupted Oral Microbiome

COVID doesn’t just cause sores directly; it can tip the balance of your mouth’s microbial ecosystem in ways that lead to secondary infections. Research comparing hospitalized COVID patients with healthy controls found a striking difference: the fungal pathogen Candida albicans was recovered from roughly half of the COVID patients but from none of the healthy controls.² Candida overgrowth in and around the mouth can produce white patches on the tongue and inner cheeks (thrush), but it can also cause angular cheilitis, the cracked, sore splits at the corners of your lips that many people mistake for cold sores or simple dryness.

Several factors stack up to encourage this fungal overgrowth during COVID. The immune dysregulation caused by SARS-CoV-2 weakens the body’s usual ability to keep Candida in check. Hospitalized patients may also receive antibiotics or corticosteroids that further shift the oral flora. And simple things like mouth breathing due to respiratory illness or reduced oral hygiene during severe illness contribute too. If your lip sores are concentrated at the corners of the mouth and appear more as cracks than blisters or ulcers, a fungal cause is worth investigating.

Nutritional Fallout

COVID-19 disrupts zinc metabolism, redistributing the mineral away from peripheral tissues toward the liver as part of the body’s inflammatory response.¹¹ Zinc deficiency is a well-known cause of angular cheilitis and slow-healing oral sores, and it also contributes to the taste disturbances that COVID patients commonly experience. The same inflammatory process that depletes zinc can affect B vitamins and iron absorption, all nutrients whose deficiency can produce cracked, sore lips. For people who had marginal nutritional status before infection, or who couldn’t eat well during illness, these deficiencies can prolong lip problems well past the acute infection.

Telling the Different Sore Types Apart

One of the challenges with COVID-related lip sores is that they can mimic so many other conditions. A review of the published literature found that most reported cases were diagnosed by clinical appearance alone, paired with a positive COVID test or other COVID symptoms, rather than by biopsy or molecular testing. The authors concluded that the existing evidence still cannot definitively confirm whether most oral lesions seen in COVID patients result from the virus’s direct action on the tissue, from the immune response, or from secondary causes like reactivated herpes or medication side effects.¹²

That uncertainty is honest and important. When you develop lip sores during or after COVID, the sore itself may be:

A direct ulcer: caused by SARS-CoV-2 infecting the lip’s mucosal cells, often appearing as one or more painful, round ulcers
A cold sore: herpes simplex reactivated by the stress and immune disruption of COVID, appearing as a cluster of small blisters, usually on the outer lip border
Erythema multiforme: an immune overreaction causing crusted, bleeding lips and target-shaped skin lesions
Angular cheilitis: cracking at the lip corners caused by Candida overgrowth or nutritional depletion
Cheilitis: generalized lip swelling, dryness, and cracking from systemic inflammation, particularly in children

A clinician can often narrow down the cause based on the appearance and location. Blisters on the outer lip border that tingle before appearing suggest herpes. Shallow ulcers inside the lip or on the inner lining point toward aphthous-like lesions. Cracks at the corners suggest fungal or nutritional causes. Widespread crusting with skin lesions elsewhere raises the possibility of erythema multiforme.

Treatment Approaches

Because the underlying cause varies, treatment depends on which type of sore you’re dealing with. A systematic review of treatments used for COVID-related oral and lip lesions found a wide range of interventions, including chlorhexidine mouthwashes, topical or systemic corticosteroids, antibiotics, antifungals, and antiviral drugs. In some cases, lesions resolved with nothing more than hydration and time.¹³

For persistent or recurring lesions, one case report described a patient whose COVID-related tongue and oral lesions initially improved with lidocaine-containing mouth rinses but kept flaring up every few weeks over a six-month period. Steroid mouthwash didn’t fully resolve the problem either. The patient eventually achieved complete resolution after photobiomodulation therapy, a form of low-level light therapy applied to the affected tissue.¹⁴ This is a single case, not a proven treatment protocol, but it illustrates that standard approaches don’t always work for COVID-related oral lesions and that clinicians may need to try escalating therapies.

For reactivated cold sores, standard antiviral treatment with valacyclovir or acyclovir remains the first-line approach. For Candida-related angular cheilitis, topical antifungal creams are the mainstay. Erythema multiforme typically requires systemic steroids. The key is getting the right diagnosis rather than treating all lip sores the same way.

How Long They Last

Most COVID-related oral and lip lesions clear up within about three weeks once the acute infection resolves. However, certain patient groups tend to have a harder time. Older adults, people with chronic diseases, those who had severe COVID, and hospitalized patients developed more extensive and longer-lasting lesions. In one extreme case, an aphthous-like ulcer on the hard palate persisted for six months.¹⁵

Recurring oral symptoms have been documented as part of long COVID. Some patients experience repeated flare-ups of mouth ulcers, tongue sensitivity, or cracked lips weeks to months after their initial infection. The case described earlier, where a patient had recurring oral lesions every three weeks for six months, fits this pattern. If you’re experiencing lip sores that keep coming back long after you’ve recovered from COVID, it’s worth mentioning to your doctor as a potential long COVID symptom rather than assuming it’s unrelated.

COVID Vaccination and Herpes Flare-Ups

It’s not only COVID infection that has been linked to lip sores. COVID vaccination, particularly mRNA-based vaccines, has been associated with herpes simplex reactivation in a small number of recipients. A systematic review and meta-analysis evaluating data from 80 studies estimated that HSV reactivation occurred at a rate of roughly 16 per 1,000 vaccinations, while varicella-zoster virus (the virus behind shingles) reactivated at about 14 per 1,000 vaccinations.¹⁶ Those are low rates, around 1-2%, and the mechanism is thought to be similar to what happens during infection: the transient immune activation and redistribution of immune resources triggered by the vaccine can create a brief window in which dormant herpes viruses reactivate.

This doesn’t mean the vaccines cause herpes or that people should avoid vaccination out of concern about cold sores. Many triggers can reactivate herpes, including other infections, sunlight exposure, menstruation, and ordinary stress. The vaccine-related reactivation risk is in the same general range as these everyday triggers. For people who know they’re prone to cold sores, having antiviral medication on hand around the time of vaccination is a reasonable precaution, but the cold sore risk is not a reason to skip vaccination given the more serious oral and systemic complications associated with COVID infection itself.

When Lip Sores Appear Before Other COVID Symptoms

One detail that catches people off guard is that oral and lip lesions can be the first symptom of COVID, appearing before fever, cough, or loss of taste. The erythema multiforme case described earlier is one example: the patient sought medical care for her oral lesions and only tested positive for COVID days later.⁷ The toddler with cheilitis presented with lip inflammation and fever as his initial COVID findings.⁹

If you develop unexplained lip sores, especially if they’re accompanied by fatigue, mild fever, or a scratchy throat, testing for COVID is worthwhile even if you haven’t developed the classic respiratory symptoms yet. This is particularly relevant during active waves of infection. It doesn’t mean every canker sore warrants a COVID test, but unusual or multiple lip lesions without a clear cause are a reasonable prompt to check.

1
PubMed Central. ACE2 and Furin Expressions in Oral Epithelial Cells Possibly Facilitate COVID-19 Infection via Respiratory and Fecal–Oral Routes
2
PubMed Central. Oral Microbiota Alterations in Subjects with SARS-CoV-2 Displaying Prevalence of the Opportunistic Fungal Pathogen Candida albicans
3
PubMed Central. Prevalence of Oral Lesions in COVID-19 Egyptian Patients
4
PubMed 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
5
PubMed Central. COVID-19 and Herpes Simplex Virus Infection: A Cross-Sectional Study
6
PubMed Central. COVID-19 infection and vaccines: potential triggers of Herpesviridae reactivation
7
PubMed Central. Erythema Multiforme as Early Manifestation of COVID-19: A Case Report
8
PubMed Central. Oral Manifestations of Exudative Erythema Multiforme in a Patient with COVID-19
9
PubMed Central. COVID-19 Infection Presenting With Cheilitis and Fever in a Toddler
10
PubMed Central. Oral manifestations of multisystemic inflammatory syndrome in children (MIS‐C) and Kawasaki disease associated to COVID‐19: A systematic review
11
PubMed Central. Treatments of COVID-19-Associated Taste and Saliva Secretory Disorders
12
PubMed Central. An integrative review of oral manifestations in patients with COVID-19: signs directly related to SARS-CoV-2 infection or secondary findings?
13
PLOS ONE. Oro-facial mucocutaneous manifestations of Coronavirus Disease-2019 (COVID-19): A systematic review
14
PubMed Central. Conservative treatment with mouthwashes followed by tongue photo biomodulation therapy in Covid-19: a case report
15
PubMed Central. Long COVID Oral Cavity Symptoms Based on Selected Clinical Cases
16
PubMed Central. Herpesviruses reactivation following COVID-19 vaccination: a systematic review and meta-analysis