What are the possible causes of a burning tongue sensation?

Causes of Burning Tongue Sensation

Burning tongue sensation has multiple potential causes that must be systematically excluded, starting with secondary causes (nutritional deficiencies, oral candidiasis, mucosal lesions, systemic diseases, and medications) before diagnosing primary burning mouth syndrome, which is a neuropathic disorder predominantly affecting peri- and post-menopausal women. 1

Secondary Causes (Must Be Excluded First)

Nutritional and Hematological Deficiencies

• Vitamin deficiencies are common culprits, with vitamin D deficiency found in 15% of patients, vitamin B2 in 15%, vitamin B6 in 5.7%, vitamin B1 in 5.3%, vitamin B12 in 0.8-4.8%, and folic acid in 0.7-2.3% of burning mouth cases 2, 3
• Iron deficiency occurs in approximately 16-19% of patients with burning tongue and commonly presents with anemia 3
• Anemia is present in nearly 20% of burning mouth patients, with normocytic anemia being most common, followed by thalassemia trait, iron deficiency anemia, and pernicious anemia 3
• These deficiencies are easily curable with replacement therapy and should be identified early to prevent irreversible systemic and neurologic damage 4

Infectious Causes

• Oral candidiasis is a fungal infection that causes burning symptoms, diagnosed by scraping and KOH preparation, and responds to topical antifungals 1, 5
• Post-herpetic neuralgia following herpes zoster can cause continuous burning, tingling, or itchy sensations at the site of previous infection 6

Local Traumatic Factors

• Mechanical trauma from sharp edges of residual tooth roots/crowns, ill-fitting dentures, or dental procedures can cause burning sensations 1, 5
• Thermal or chemical injury to the oral mucosa should be identified on examination 1
• Post-traumatic trigeminal neuropathic pain can develop within 3-6 months following dental procedures (root canals, extractions, implants) or facial trauma, presenting as continuous burning or tingling 6

Systemic and Endocrine Disorders

• Diabetes mellitus with elevated fasting glucose (found in 23.7% of burning mouth patients) or HbA1c can cause neuropathic burning 1, 2
• Thyroid disorders, particularly hyperthyroidism, cause tongue erythema and burning, with abnormal TSH found in 3.2-5.2% of patients 5, 2
• Autoimmune diseases including Sjögren's syndrome and sicca syndrome manifest with oral burning and must be excluded 5
• Pernicious anemia with serum gastric parietal cell antibody positivity (12.3% of burning mouth patients) causes burning tongue 3

Medication Side Effects

• Pharmacological side effects from various medications can cause oral burning and must be reviewed in the medication history 6, 5

Primary Burning Mouth Syndrome

When to Diagnose

• Primary BMS should only be diagnosed after excluding all secondary causes through thorough examination and laboratory testing 1
• This is a disorder of peripheral nerve fibers with central nervous system changes, confirmed through neurophysiological testing, biopsies, and functional MRI 5

Clinical Characteristics

• Location: Most commonly affects the tongue tip bilaterally, lips, palate, and buccal mucosa, with normal-appearing oral mucosa on examination 6, 5
• Quality: Continuous burning, stinging, or itchy sensation with severity ranging from mild to severe 6, 7
• Demographics: Predominantly affects peri- and post-menopausal women 6, 5
• Associated symptoms: Dry mouth (48.1%), abnormal taste (16.7%), numbness of oral mucosa (30.7%), depression, and poor quality of life 5, 3

Diagnostic Workup Algorithm

Essential Laboratory Tests

1. Complete blood count with differential to identify anemia 1, 5
2. Iron studies (ferritin, serum iron, TIBC) for iron deficiency 1, 5
3. Vitamin B12 level as deficiency is well-established cause 1, 5
4. Fasting glucose and HbA1c for diabetes screening 1
5. Vitamin D 25(OH) level given 15% deficiency rate 1, 2
6. Thyroid function tests (TSH, free T4) for thyroid disorders 1
7. Folate level to exclude folic acid deficiency 1

Clinical Examination

• Thorough oral examination to identify visible mucosal lesions, candidiasis, or traumatic factors 1, 5
• Document onset timing, medication use, systemic diseases, and dental procedures in the history 5
• Tongue biopsy or referral if suspicious lesions, unilateral pain, ulceration, or non-healing lesions are present 1, 5

Common Pitfalls to Avoid

• Do not diagnose primary BMS without excluding secondary causes, as nutritional deficiencies are easily treatable and failure to identify them can lead to irreversible damage 4
• Do not perform non-indicated substitution therapy for suspected but unproven deficiency states 8
• Recognize that multiple nutritional deficiencies commonly coexist, complicating the clinical picture and requiring comprehensive laboratory screening rather than clinical impression alone 4