What is burning mouth syndrome?

What is Burning Mouth Syndrome

Burning mouth syndrome (BMS) is a chronic pain disorder characterized by a continuous burning, stinging, or scalding sensation of the oral mucosa—most commonly affecting the tongue tip, lips, palate, and buccal mucosa—in the absence of any visible mucosal lesions or abnormalities on examination. 1, 2

Clinical Characteristics

• BMS predominantly affects peri- and post-menopausal women, with an estimated prevalence of 0.7-4.6% in the general population 2, 3
• The burning sensation is typically bilateral, continuous, and spontaneous, often described as if the mouth or tongue were scalded or on fire 2, 3
• Pain severity ranges from mild to severe and significantly impacts quality of life 1

Associated Symptoms

• Dry mouth (xerostomia) is commonly reported alongside the burning sensation 1, 4
• Abnormal taste (dysgeusia) frequently accompanies BMS 1, 4
• Depression and psychological distress are often present and may contribute to symptom severity 1, 2

Classification: Primary vs. Secondary BMS

Primary (Idiopathic) BMS

• Primary BMS is considered a disorder of peripheral nerve fibers with central nervous system changes, confirmed through neurophysiological testing, biopsies, and functional MRI 2
• Tongue biopsies show significantly lower density of epithelial nerve fibers compared to controls, supporting a neuropathic etiology 2, 5
• This diagnosis is made only after excluding all secondary causes 2, 5

Secondary BMS

Secondary BMS results from identifiable precipitating factors that must be systematically excluded 2, 5:

Local oral factors:

• Oral candidiasis (diagnosed by scraping and KOH preparation) 2
• Mucosal lesions from traumatic ulceration, sharp edges of dental work, thermal burns, or chemical injury 2

Systemic factors:

• Hematological disorders including anemia, vitamin B12 deficiency, and iron deficiency 2
• Autoimmune diseases such as Sjögren's syndrome and sicca syndrome 2
• Thyroid disorders, particularly hyperthyroidism causing tongue erythema 2

Other causes:

• Pharmacological side effects from various medications 2
• Post-traumatic trigeminal neuropathic pain and post-herpetic neuralgia 2
• Nutritional deficiencies and hormonal changes 3, 4

Diagnostic Approach

The diagnosis requires a systematic exclusion process 2, 5:

• Obtain detailed clinical history focusing on onset timing, medication use, systemic diseases, and recent dental procedures 2
• Perform thorough oral examination to identify any mucosal lesions, candidiasis, or traumatic factors 2
• Order complete blood count with differential to identify anemia 2
• Check vitamin B12 levels as deficiency is a well-established cause 2
• Obtain iron studies (ferritin, serum iron, TIBC) as iron deficiency frequently presents with burning tongue 2
• Consider qualitative sensory testing if neuropathic etiology is suspected 2
• Consider biopsy only if mucosal abnormalities are present or diagnosis remains uncertain 2

Important Clinical Considerations

• In more than one-third of patients, multiple concurrent causes may be identified, requiring comprehensive evaluation 3
• The condition is often multifactorial with interactions among local, systemic, and psychogenic factors 5, 6
• Professional delay in diagnosing and appropriately managing BMS patients occurs frequently 3
• The etiopathogenesis remains complex and not fully understood despite emerging evidence for neuropathic mechanisms 5, 6