What are the causes of localized burning of the tongue?

Causes of Localized Burning of the Tongue

Localized burning of the tongue is most commonly caused by secondary factors including thermal/chemical injury, oral candidiasis, traumatic lesions from sharp dental edges or ill-fitting dentures, nutritional deficiencies (iron, B12, B2, B6, zinc), post-herpetic neuralgia, post-traumatic trigeminal neuropathy, and medication side effects—all of which must be systematically excluded before diagnosing primary burning mouth syndrome. 1, 2, 3

Local Traumatic and Infectious Causes

Direct tissue injury is a frequent culprit:

• Thermal burns from hot foods or beverages cause localized erosions or ulcers, particularly on the palate or tongue, and may occur more readily in diabetic patients with oral mucosal dysesthesia 4
• Chemical injury from acids or alkalis produces erythema, edema, and pain through inflammatory mediator release 5
• Mechanical trauma from sharp edges of residual tooth roots/crowns or ill-fitting dentures creates focal burning and pain 1, 3

Oral candidiasis presents with burning symptoms and must be diagnosed via scraping with KOH preparation or oral swabs if fungal infection is suspected 1, 3

Nutritional and Hematologic Deficiencies

Essential laboratory workup should include 1, 3:

• Complete blood count with differential to identify anemia, a common cause of oral burning 3
• Iron studies (ferritin, serum iron, TIBC) as iron deficiency frequently presents with burning tongue 3
• Vitamin B12 levels, as deficiency is a well-established cause of secondary burning mouth syndrome 1, 3
• Riboflavin (B2) deficiency manifests with glossitis, cheilosis, and angular stomatitis 3
• Pyridoxine (B6) deficiency causes glossitis and seborrheic dermatitis with cheilosis 3
• Zinc deficiency leads to glossitis and taste alterations 3

Additional screening should include fasting glucose, HbA1c, vitamin D 25(OH), and thyroid function tests (TSH, free T4) 1

Neuropathic Causes

Post-traumatic trigeminal neuropathic pain develops 3-6 months following dental procedures or facial trauma, presenting as continuous burning or tingling within the trigeminal distribution 1

Post-herpetic neuralgia following herpes zoster causes persistent burning, tingling, or itchy sensations at the site of previous infection with accompanying allodynia and hyperalgesia 1

Herpes zoster oticus (Ramsay Hunt syndrome) produces severe otalgia, vesicles on the external ear canal, facial paralysis, and loss of taste on the anterior two-thirds of the tongue 5

Systemic and Autoimmune Conditions

Autoimmune diseases including Sjögren's syndrome and sicca syndrome manifest with oral burning and xerostomia 3

Thyroid disorders, particularly hyperthyroidism, can cause tongue erythema and burning 3

Connective tissue diseases and endocrine disorders require systematic evaluation 6

Medication-Related Causes

Pharmacological side effects from various medications can produce oral burning and must be reviewed in the medication history 1, 3

Allergic Contact Reactions

Allergic contact dermatitis occurs in susceptible individuals exposed to metals (nickel, silver), chemicals (cosmetics, soaps), plastics, or drugs, producing maculopapular and eczematous eruptions 5

Diagnostic Algorithm

1. Thorough oral examination to identify visible mucosal lesions, traumatic factors, or candidiasis 1, 3
2. Document onset timing, duration, character, and location specificity of pain, noting any recent dental procedures or facial trauma within the preceding 3-6 months 1
3. Complete laboratory workup as outlined above to exclude secondary causes 1, 3
4. Consider tongue biopsy if suspicious lesions are present, unilateral pain, ulceration, or non-healing lesions to rule out malignancy 1
5. Qualitative sensory testing if neuropathic etiology is suspected 3

Primary Burning Mouth Syndrome

Only after excluding all secondary causes should primary BMS be diagnosed, which represents a chronic neuropathic pain condition involving peripheral nerve fiber dysfunction with central nervous system alterations 1, 2, 3. Primary BMS typically presents with bilateral involvement of the tongue tip and anterior two-thirds, with normal-appearing oral mucosa on examination 1, 7. This condition predominantly affects peri- and post-menopausal women and follows a chronic course with low likelihood of spontaneous remission 1, 2.

Critical Pitfalls to Avoid

• Failing to perform comprehensive laboratory screening before diagnosing primary BMS leads to missed treatable secondary causes 1, 3
• Not documenting the temporal relationship between dental procedures/trauma and symptom onset may miss post-traumatic neuropathy 1
• Overlooking medication review as a routine step misses drug-induced oral burning 1, 3
• Assuming bilateral symptoms exclude secondary causes—nutritional deficiencies and systemic conditions can present bilaterally 3, 8