What is Burning Mouth Syndrome?
Burning mouth syndrome is a chronic pain condition characterized by a burning, stinging, or itchy sensation of the oral mucosa without any visible mucosal abnormalities, predominantly affecting peri- and post-menopausal women, most commonly on the tongue tip, lips, palate, and buccal mucosa. 1
Clinical Characteristics
Primary BMS represents a disorder of peripheral nerve fibers with central nervous system changes, confirmed through neurophysiological testing, biopsies, and functional MRI. 2 The condition manifests as:
- Continuous burning sensation affecting the tongue tip bilaterally, lips, palate, and buccal mucosa, with completely normal-appearing oral mucosa on examination 2, 3
- Pain severity ranging from mild to severe, often worsening during the day, with stress, fatigue, or when eating spicy/hot foods 1, 4
- Associated symptoms including dry mouth (xerostomia), abnormal taste (dysgeusia), depression, and significantly impaired quality of life 1, 2
- Reduced epithelial nerve fiber density in tongue biopsies compared to healthy controls, supporting the neuropathic origin 2
Epidemiology and Demographics
The condition affects approximately 0.7-4.6% of the general population, with about 1.3 million American adults afflicted. 5 It predominantly affects middle-aged and elderly women, particularly those in the peri- and post-menopausal period with hormonal changes. 1, 6
Classification: Primary vs. Secondary BMS
Primary (Idiopathic) BMS
This is the essential form where no organic local or systemic causes can be identified, and a neuropathic pathogenesis is likely. 7 Diagnosis depends on exclusion of all secondary causes. 2, 7
Secondary BMS
This results from identifiable precipitating factors that must be systematically excluded: 2, 3
Local factors:
- Oral candidiasis (fungal infection diagnosed by scraping and KOH preparation) 2
- Mucosal lesions from traumatic ulceration, sharp edges of residual tooth roots/crowns, ill-fitting dentures, thermal burns, or chemical injury 2, 3
Systemic factors:
- Hematological disorders (anemia, iron deficiency, vitamin B12 deficiency) 2, 3
- Autoimmune diseases (Sjögren's syndrome, sicca syndrome) 2
- Thyroid disorders, particularly hyperthyroidism causing tongue erythema 2
- Diabetes mellitus 3
- Nutritional deficiencies (vitamins, zinc) 7
Neurological causes:
- Post-traumatic trigeminal neuropathic pain (developing 3-6 months after dental procedures or facial trauma) 3
- Post-herpetic neuralgia following herpes zoster 2, 3
Pharmacological side effects from various medications 2, 3
Diagnostic Approach
The diagnosis requires a systematic exclusion process: 2, 3
- Detailed clinical history focusing on onset timing, medication use, systemic diseases, and recent dental procedures 2
- Thorough oral examination to identify any mucosal lesions, candidiasis, or traumatic factors 2, 3
- Essential laboratory workup including complete blood count with differential, vitamin B12 levels, iron studies (ferritin, serum iron, TIBC), fasting glucose and HbA1c, vitamin D 25(OH), and thyroid function tests (TSH, free T4) 2, 3
- Oral swabs if fungal or bacterial infection is suspected 1
- Tongue biopsy if mucosal abnormalities are present, diagnosis is uncertain, or there is unilateral pain, ulceration, or non-healing lesions to rule out malignancy 2, 3
Important Clinical Pitfalls
Avoid inadequate reassurance—failing to emphasize that the condition will not worsen is crucial, as this represents a fundamental therapeutic element and helps reduce patient anxiety. 1
Be aware of "complicated BMS" where overlapping oral mucosal pathologies (such as infections) may cause diagnostic difficulties. 6 In more than one-third of patients, multiple concurrent causes may be identified. 5
Treatment failures are common in BMS management, and patients should be informed about the chronic nature of the condition with generally unfavorable prognosis—only a small number achieve complete resolution. 1