Burning Tongue COVID: Causes, Oral Symptoms, and Relief Tips

Some individuals recovering from COVID-19 report an unusual burning sensation in their tongue, often described as tingling, irritation, or discomfort. This symptom can persist even after other signs of infection subside. While not as widely recognized as fever or cough, oral symptoms have been increasingly documented in relation to the virus.

Understanding why this occurs requires examining how COVID-19 affects the mouth, nerves, and immune system.

Oral Mucosal Changes During Infection

The oral mucosa, which lines the inside of the mouth, plays a crucial role in protecting against pathogens. During a COVID-19 infection, this tissue can undergo significant changes, contributing to symptoms such as a burning tongue. One key factor is the high expression of angiotensin-converting enzyme 2 (ACE2) receptors in the oral epithelium. SARS-CoV-2, the virus responsible for COVID-19, uses these receptors to enter cells, leading to direct viral invasion of the mucosal lining. A study published in Nature Medicine found that ACE2 expression is particularly high in the tongue and salivary glands, making these areas especially vulnerable to viral damage. This can result in inflammation, increased sensitivity, and disruptions in normal oral function.

As the virus interacts with mucosal cells, it can trigger desquamation, or the shedding of the epithelial layer, exposing underlying nerve endings and heightening sensitivity. A systematic review in The Journal of Oral Pathology & Medicine reported that patients with COVID-19 frequently experience mucosal ulcerations, erythema, and atrophic changes, all of which can exacerbate oral discomfort. Additionally, SARS-CoV-2 infection can alter saliva composition, reducing its protective properties. Saliva contains antimicrobial peptides and enzymes that help maintain a balanced oral microbiome, but studies have shown that infection can lead to decreased salivary flow and biochemical changes. This reduction in saliva can contribute to dryness, further irritating the mucosa and intensifying burning sensations.

COVID-19 also disrupts the oral microbiome. Research in Frontiers in Cellular and Infection Microbiology has highlighted that the virus can cause microbial imbalances, promoting the overgrowth of opportunistic pathogens such as Candida species, which are known to cause oral thrush and burning sensations. Patients with COVID-19 have shown higher rates of fungal infections in the oral cavity, likely due to both direct viral effects and the use of medications such as corticosteroids and antibiotics, which further disturb microbial balance.

Sensory Nerve Involvement In Burning Sensations

The burning sensation in the tongue following COVID-19 infection is linked to sensory nerve involvement, particularly the trigeminal and glossopharyngeal nerves, which transmit pain, temperature, and tactile information from the oral cavity to the brain. SARS-CoV-2 has been shown to affect both peripheral and central nervous system structures, potentially leading to neuropathic symptoms such as tingling and burning. A study published in Pain Reports highlighted that post-viral neuropathy, observed after infections like herpes simplex and varicella-zoster, may also occur following COVID-19, explaining persistent oral discomfort in some individuals.

The virus may contribute to nerve irritation by inducing neuroinflammation. Research in Brain, Behavior, and Immunity suggests that SARS-CoV-2 can infect nerve cells via ACE2 receptors and neuropilin-1, triggering an inflammatory cascade that alters pain perception. This is particularly relevant in the oral cavity, where small unmyelinated nerve fibers, known as C-fibers, detect thermal and chemical stimuli. Damage or heightened sensitivity in these fibers can lead to burning pain, similar to what is observed in burning mouth syndrome (BMS).

Systemic inflammation associated with COVID-19 can further contribute to nerve dysfunction. Elevated levels of pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), have been implicated in neuropathic pain conditions. A meta-analysis in The Journal of Neuroinflammation found that increased cytokine activity can lead to peripheral nerve hyperexcitability, making affected individuals more susceptible to abnormal sensations. This could explain why some COVID-19 patients report persistent burning sensations in the tongue even after recovering from the acute phase of the illness.

Another potential mechanism involves vascular changes affecting nerve function. COVID-19 has been linked to endothelial dysfunction and microvascular damage, which can impair blood flow to peripheral nerves. A study in The Lancet Neurology reported that post-COVID neuropathic symptoms may arise due to ischemic injury in small nerve fibers, leading to altered sensation and discomfort. In the oral cavity, compromised blood supply to sensory nerves may worsen burning sensations, particularly in individuals with preexisting conditions such as diabetes or neuropathy.

Immune Responses In The Oral Cavity

The immune system’s role in the oral cavity extends beyond pathogen defense, influencing inflammation, tissue integrity, and pain perception. When COVID-19 enters the body, the oral mucosa serves as one of the first points of interaction between the virus and the immune response. This interaction triggers localized immune activation, contributing to symptoms like a burning tongue. The presence of SARS-CoV-2 in salivary glands and oral tissues prompts an innate immune reaction, releasing interferons and other antiviral cytokines. These molecules limit viral replication but also promote inflammatory pathways that heighten tissue sensitivity.

As the immune system responds, macrophages and T cells infiltrate the oral mucosa, producing pro-inflammatory mediators such as interleukin-1 beta (IL-1β) and TNF-α. This inflammatory cascade disrupts epithelial cell function, increasing mucosal permeability. A compromised barrier allows irritants and microbes to interact more directly with nerves, exacerbating discomfort. Similar immune responses have been observed in other viral infections affecting the oral cavity, such as herpes simplex virus and Epstein-Barr virus, where prolonged inflammation contributes to persistent symptoms.

Beyond mucosal effects, the immune response also affects salivary gland function. SARS-CoV-2 has been detected in saliva, and studies suggest that infection can lead to immune-mediated damage to the salivary glands. This can result in reduced saliva production, impairing oral lubrication and antimicrobial properties. Saliva helps regulate bacterial and fungal populations, and disruptions can increase the risk of opportunistic infections such as oral candidiasis, further intensifying burning sensations.

Additional Oral Manifestations

Beyond a burning tongue, individuals recovering from COVID-19 have reported a range of oral symptoms reflecting underlying physiological disruptions. One frequently observed issue is dysgeusia, or altered taste perception, which can manifest as a metallic, bitter, or diminished sense of taste. This change can persist for weeks, with some patients experiencing prolonged difficulty detecting certain flavors. Studies suggest that SARS-CoV-2 can interfere with taste receptor function, particularly in the fungiform papillae of the tongue, where taste buds are concentrated.

Dry mouth, or xerostomia, is another common complaint among post-COVID patients, often linked to decreased salivary gland activity. Saliva plays a critical role in maintaining oral hydration and preventing irritation, and its reduction can lead to difficulties in speaking, chewing, and swallowing. Persistent dryness may also increase the risk of complications such as dental caries and gum inflammation, as the natural cleansing action of saliva is diminished. Some patients report a sticky or thickened consistency of saliva, further contributing to discomfort.