Burning Mouth Syndrome (BMS) is defined by a persistent, painful, burning sensation in the mouth that occurs without any visible physical signs or lesions upon clinical examination. This chronic intraoral pain must be present for more than two hours a day over a period exceeding three months to fit the diagnostic criteria. When the cause of this discomfort cannot be identified, it is classified as primary BMS, suggesting a neuropathic origin. However, the difficulty in diagnosis lies in the many other local and systemic health issues that can produce a nearly identical secondary burning sensation. Understanding these mimics is paramount, as treating the underlying condition can completely resolve the symptoms, thereby preventing a misdiagnosis of true BMS.
Local Oral Causes of Burning Sensation
Conditions originating directly within the oral cavity can create a burning sensation, but unlike BMS, these typically present with observable clinical features or a clear local trigger. Oral candidiasis, a fungal infection caused by an overgrowth of Candida species, frequently results in burning, especially on the tongue and palate. This infection often presents with white, removable plaques and underlying redness, which immediately distinguishes it from the visually normal mucosa seen in primary BMS.
Geographic tongue (benign migratory glossitis) is another local mimic, causing sensitivity and burning discomfort, particularly after consuming acidic or spicy foods. This condition is characterized by distinct, shifting patches of smoothness on the tongue surface where the filiform papillae have atrophied. Contact stomatitis and allergic reactions can also cause oral burning, often triggered by ingredients in dental products or by metals and acrylics used in dental restorations. Patch testing can confirm a hypersensitivity reaction to these materials.
Mechanical irritation from poorly fitting dental prostheses or sharp edges on a tooth can cause localized trauma and subsequent chronic discomfort. Parafunctional habits, such as chronic teeth clenching (bruxism), can also irritate the soft tissues and lead to a persistent burning feeling. In these local cases, the pain is often unilateral or focused on the site of irritation, which contrasts with the typically bilateral and diffuse pain distribution of primary BMS.
Systemic Diseases and Nutritional Deficiencies
Oral burning can be a manifestation of an underlying systemic health problem, requiring a broader medical investigation beyond the mouth. Several nutritional deficiencies directly impact the health of the oral mucosa and taste buds. Deficiencies in iron, zinc, and B-vitamins (specifically B1, B2, B6, and B12) have been implicated as causes of secondary oral burning. These micronutrients are necessary for the normal regeneration of epithelial cells, and a shortage can lead to atrophic glossitis, resulting in a smooth, red, and painful tongue.
Metabolic and endocrine disorders also figure prominently among the systemic causes of oral burning. Uncontrolled Type 2 Diabetes Mellitus can lead to small fiber neuropathy, where nerve damage manifests as a burning sensation in the mouth, alongside changes in saliva composition that increase irritation. Hormonal fluctuations, particularly the decrease in estrogen levels associated with menopause, can lead to atrophic changes in the oral mucosa, making the tissues more susceptible to inflammation and a burning feeling.
Sjögren’s Syndrome, an autoimmune disease, causes severe dry mouth (xerostomia) by attacking the salivary glands. This chronic lack of lubricating saliva drastically increases friction and irritation, which patients perceive as a persistent burning discomfort. Gastroesophageal Reflux Disease (GERD), particularly silent reflux, can also be a hidden culprit. Stomach acid vapor can rise into the throat and mouth, irritating the delicate oral tissues, with the burning sensation often being most noticeable upon waking. Identifying these underlying systemic issues is necessary, as treating the deficiency or disease often resolves the oral symptoms.
Medication-Induced Symptoms and Nerve Disorders
A burning sensation can arise as a side effect of certain pharmaceuticals, which is a form of secondary BMS that resolves upon adjusting the medication. Many medications cause xerostomia (dry mouth), a significant contributor to oral burning, including certain antidepressants, antihistamines, and neuroleptics. Some Angiotensin-Converting Enzyme (ACE) inhibitors, a class of blood pressure medication, are also known to induce oral discomfort and taste changes in some patients.
The mechanism for drug-induced symptoms is not always related to dryness. For example, ACE inhibitors like captopril may increase levels of bradykinin, which is thought to irritate the nerve endings in the mouth. Other drugs, such as the antiepileptic topiramate, have also been reported to cause BMS-like symptoms. Differentiating these cases from primary BMS involves a detailed review of the patient’s medication history, with symptoms typically improving after the problematic drug is altered or discontinued.
True BMS is understood to be a primary neuropathic pain disorder involving dysfunction of the trigeminal nerve, but other distinct nerve pathologies can produce a similar feeling. For instance, atypical presentations of Trigeminal Neuralgia or Post-Herpetic Neuralgia can sometimes include a burning or tingling sensation before the onset of classic sharp, intense pain. Psychological factors like chronic anxiety, depression, and stress are frequently associated with or can worsen the symptoms of oral burning.
The Differential Diagnostic Process
The diagnosis of primary Burning Mouth Syndrome is one of exclusion, meaning all other possible causes must be systematically ruled out. The initial consultation begins with a meticulous review of the patient’s medical history, pain characteristics, and a thorough intraoral examination to check for visible lesions or mechanical irritants. Blood tests are a necessary step in the workup, targeting nutritional deficiencies (like iron and B-vitamins) and screening for systemic conditions such as diabetes and thyroid dysfunction.
If a local allergy is suspected, patch testing may be performed to identify hypersensitivity to dental materials or common food and product additives. Microbiological swabs are also used to rule out active infections, such as oral candidiasis. Only after this comprehensive process of elimination—where local, systemic, medication-related, and other neuropathic causes have been investigated and excluded—can a diagnosis of primary BMS be confidently assigned.