Burning Tongue

Burning tongue is a burning or dysaesthetic sensation of the tongue and often other oral sites, present daily for more than 2 hours a day for over 3 months, with a normal appearing mucosa and no clinical lesions to account for it. When no cause is found it is called burning mouth syndrome, a chronic neuropathic pain disorder.

• Primary (idiopathic) burning mouth syndrome: small fibre and central nervous system dysfunction affecting the trigeminal and gustatory nerves, with a component of hormonal change and psychological factors.
• Secondary burning (the cause must be excluded): candidiasis, iron, vitamin B12, folate or zinc deficiency, diabetes mellitus, hypothyroidism, dry mouth and Sjogren syndrome, lichen planus, geographic tongue, allergy or contact reaction (cinnamon, mint, flavourings, dental materials such as mercury, acrylic, nickel), reflux, oral parafunction (tongue thrusting, bruxism), ill fitting dentures, drug effects (angiotensin converting enzyme inhibitors, protease inhibitors, benzodiazepine withdrawal), nutritional deficiency, vitamin deficiency in alcohol misuse, and neuropathy (post-herpetic or trigeminal).
• Affects up to 1 to 4 percent of the general population, predominantly women aged 50 to 70 around and after menopause.
• Coexists with anxiety, depression and sleep disturbance, and can affect quality of life significantly; it is not a sign of cancer.

• Burning, scalding or tingling of the tip and sides of the tongue, anterior hard palate, lips and inner cheeks; usually bilateral and symmetrical.
• Pattern: low or absent on waking, builds through the day to peak in the evening; often relieved by eating or drinking and distraction; may worsen with stress and acidic or spicy foods.
• Associated: dry mouth sensation, altered taste (bitter or metallic), thirst, and taste loss.
• Examination: oral mucosa appears normal in primary disease; look for candidiasis, atrophic glossitis (smooth red tongue in anaemia), fissured tongue, geographic tongue, lichen planus, denture trauma, dry mouth, tongue thrusting, and teeth grinding.
• Red flags: unilateral symptoms with lesion, ulcer, red or white patch, sensory loss or weakness (neurological disease, malignancy), systemic features (weight loss, fever), tongue swelling (angio oedema, amyloid).

• Clinical diagnosis by exclusion; document pain scale, timing, triggers, medicines and psychological state.
• Tests to find secondary causes: FBC, ferritin, vitamin B12, folate, zinc (if indicated), HbA1c, thyroid function, ESR, CRP, antinuclear antibodies and anti-Ro and anti-La (if dry mouth or eyes), coeliac serology.
• Microbiology: oral swab or rinse for candida; consider salivary flow measurement.
• Patch testing for allergies to flavourings, dental materials and metals if clinically suggested.
• Review of denture fit and occlusion; assess reflux.
• Screen mood and anxiety (PHQ-9, GAD-7); MRI brain and trigeminal nerve for neurological signs.
• Differentials: oral candidiasis, nutritional glossitis, geographic tongue, lichen planus, dry mouth, allergic contact stomatitis, trigeminal neuralgia, glossopharyngeal neuralgia, atypical odontalgia, and psychogenic pain.

Treat secondary causes

• Candidiasis: miconazole oral gel 2.5 mL four times daily for 7 days (continue 2 days after resolution), or nystatin suspension 100 000 units/mL 1 mL four times daily for 7 days; treat dentures.
• Replace deficiencies: iron (ferrous sulfate 200 mg daily), B12 (hydroxocobalamin 1 mg intramuscularly alternate days for 2 weeks then every 3 months, or oral cyanocobalamin 1000 micrograms daily), folic acid 5 mg daily for 4 months, and zinc.
• Control diabetes, treat hypothyroidism (levothyroxine), replace or adjust ill fitting dentures, stop or substitute implicated drugs, manage reflux, treat dry mouth, and avoid allergens (cinnamon flavoured and mint products).

General measures for primary burning mouth syndrome

• Reassure and explain that the condition is benign, not cancer, and often improves slowly (some patients improve spontaneously over years, and most improve with treatment).
• Avoid triggers: tobacco, alcohol, acidic and spicy foods and drinks, strong mouthwashes, and tartar control or whitening toothpaste; use a mild fluoride toothpaste without sodium lauryl sulfate.
• Sip water through the day, use ice chips, sugar free gum, saliva substitutes if dry; stress management and sleep hygiene.

Topical therapy (first line)

• Clonazepam 0.5 mg tablet: let it dissolve slowly in the mouth for 3 minutes, keep the saliva in contact with the painful areas, then spit out (do not swallow), three times daily for 14 days; if effective continue at the lowest frequency; limit use to avoid sedation, dependence, and withdrawal.
• Capsaicin 0.025 percent cream or rinse (dilute) applied to the tongue three times daily, starting with a low dose for tolerance (initial burning improves).
• Lidocaine 2 percent viscous solution 5 mL as a rinse, spat out, up to four times daily for short term relief; benzydamine 0.15 percent mouthwash 15 mL, spat out, up to four times daily.
• Alpha lipoic acid 600 mg orally daily for 2 months (evidence modest).

Systemic therapy (when topical measures fail)

• Amitriptyline 10 mg orally at night, increasing by 10 mg every 1 to 2 weeks to 25 to 50 mg (avoid in glaucoma, arrhythmia, urinary retention; worsens dry mouth), or nortriptyline 10 mg at night increasing to 50 mg.
• Duloxetine 30 mg daily increasing to 60 mg after 2 weeks; avoid with uncontrolled hypertension and severe liver disease.
• Gabapentin 100 mg three times daily increasing weekly to 300 to 600 mg three times daily, or pregabalin 75 mg twice daily increasing to 150 mg twice daily (renal dose adjustment).
• Allow 6 to 8 weeks at an adequate dose before judging response.

Psychological therapy

• Cognitive behavioural therapy and mindfulness reduce pain intensity; treat depression and anxiety.

Follow up

• Review every 4 to 6 weeks while treatment is adjusted, then every 3 to 6 months; refer to oral medicine, neurology or pain services for refractory pain or when a lesion or neurological sign appears.