What are the non-drug causes of burning tongue and burning mouth syndrome?

Non-Drug Causes of Burning Tongue and Burning Mouth Syndrome

Secondary burning mouth syndrome has multiple non-drug etiologies that must be systematically excluded before diagnosing primary BMS, including oral infections, nutritional deficiencies, autoimmune conditions, hematological disorders, mucosal lesions, and traumatic factors. 1, 2, 3

Local Oral Causes

Infectious Causes

• Oral candidiasis is a fungal infection that causes burning mouth symptoms and must be diagnosed by scraping and KOH preparation 3
• This is one of the most common treatable causes of oral burning that mimics BMS 1

Traumatic and Mechanical Factors

• Sharp edges of residual tooth roots or crowns can cause localized burning and irritation 3, 4
• Ill-fitting dentures may create chronic trauma leading to burning sensations 4
• Thermal burns from hot foods or beverages can produce burning symptoms 3
• Chemical injury from irritating substances or oral care products containing alcohol or strong flavoring agents 2, 3

Mucosal Lesions

• Traumatic ulceration from mechanical injury requires identification and removal of the causative factor 3
• Any visible mucosal abnormality should prompt consideration of biopsy, especially with unilateral pain or non-healing lesions 4

Systemic Causes

Nutritional and Hematological Deficiencies

• Vitamin B12 deficiency is a well-established cause of secondary BMS and should be checked in all patients 3, 4
• Iron deficiency anemia frequently presents with burning tongue and requires iron studies (ferritin, serum iron, TIBC) 3, 4
• Anemia of any cause commonly produces oral burning symptoms, necessitating a complete blood count with differential 3, 4
• Vitamin D deficiency may contribute to oral burning and should be assessed with 25(OH) vitamin D levels 4

Autoimmune and Endocrine Disorders

• Sjögren's syndrome and sicca syndrome can manifest with oral burning and must be excluded before diagnosing primary BMS 3
• Thyroid disorders, particularly hyperthyroidism, can cause tongue erythema and burning sensations 3
• Thyroid function tests (TSH, free T4) are essential in the diagnostic workup 4
• Other autoimmune diseases should be considered as potential contributors 1, 2

Metabolic Conditions

• Diabetes mellitus can cause neuropathic changes leading to oral burning 4, 5
• Fasting glucose and HbA1c should be checked to identify uncontrolled diabetes 4

Neuropathic Causes

Post-Infectious Neuropathy

• Post-herpetic neuralgia following herpes zoster causes continuous burning, tingling, or itchy sensations at the site of previous infection 1, 4
• This presents with allodynia and hyperalgesia in the affected trigeminal distribution 1

Post-Traumatic Neuropathy

• Post-traumatic trigeminal neuropathic pain develops within 3-6 months following dental procedures or facial trauma 1, 4
• Presents as continuous burning or tingling with possible allodynia or other sensory changes 1
• Qualitative sensory testing may help confirm neuropathic etiology 1, 3

Other Systemic Conditions

• Scarlet fever and Kawasaki disease can present with oral burning symptoms, though these are less common in adults 3

Diagnostic Algorithm

Step 1: Thorough oral examination to identify visible mucosal lesions, candidiasis, traumatic factors, or ill-fitting dental appliances 3, 4

Step 2: Detailed clinical history focusing on:

• Onset timing and duration of symptoms 4
• Recent dental procedures or facial trauma 3, 4
• Medication use (covered separately as drug causes) 3
• Systemic diseases 4

Step 3: Essential laboratory workup including:

• Complete blood count with differential 3, 4
• Iron studies (ferritin, serum iron, TIBC) 3, 4
• Vitamin B12 level 3, 4
• Fasting glucose and HbA1c 4
• Thyroid function tests (TSH, free T4) 4
• Vitamin D 25(OH) level 4

Step 4: Consider biopsy if mucosal abnormalities are present, diagnosis is uncertain, or there is unilateral pain with non-healing lesions 3, 4

Critical Pitfalls to Avoid

• Failing to exclude secondary causes before diagnosing primary BMS leads to missed treatable conditions 3, 6, 7
• Professional delay in diagnosis occurs frequently and prolongs patient suffering 5
• Overlooking multiple concurrent causes, as more than one-third of patients have multiple contributing factors 5
• Missing nutritional deficiencies that are easily treatable with supplementation 3, 4
• Not recognizing neuropathic causes such as post-herpetic neuralgia or post-traumatic trigeminal pain that require different management approaches 1, 4

Important Clinical Context

Primary BMS is a diagnosis of exclusion that should only be established after all secondary causes have been ruled out 3, 5, 6, 7. The condition predominantly affects peri- and post-menopausal women, with onset typically occurring within 3-12 years after menopause 8. Primary BMS is now understood to be a disorder of peripheral nerve fibers with central nervous system changes, confirmed by significantly lower density of epithelial nerve fibers in tongue biopsies compared to controls 3, 8.