What are the causes of black tongue?

Causes of Black Tongue

Black tongue is most commonly caused by black hairy tongue (lingua villosa nigra), a benign condition resulting from elongation and hyperkeratosis of filiform papillae that trap bacteria, food debris, and pigments, with predisposing factors including poor oral hygiene, smoking, antibiotics (especially linezolid), immunosuppression, and soft diets. 1

Primary Mechanism: Black Hairy Tongue

• Black hairy tongue occurs when filiform papillae on the tongue dorsum become elongated and hyperkeratotic, creating a hair-like appearance that accumulates fungi, bacteria, and pigments from food or other debris, leading to discoloration ranging from yellow-brown to black 1, 2
• The condition is benign and self-limiting, though it may persist without intervention 1, 2
• Symptoms beyond appearance are uncommon but may include bad breath (halitosis), metallic taste, gagging, or nausea 3, 2

Medication-Induced Black Tongue

Linezolid (Priority Drug Label Evidence)

• Linezolid specifically causes superficial tongue discoloration and tooth discoloration as documented adverse effects, with the tooth discoloration being removable with professional dental cleaning in cases with known outcome 4
• Tongue discoloration has been reported in 1.1% of patients receiving linezolid 400 mg PO q12h and 0.2% of patients receiving 600 mg q12h in controlled trials 4
• This is a benign and reversible condition that resolves after discontinuation of the medication 5

Other Antibiotics and Medications

• Topical or systemic antibiotics are well-established predisposing factors for black hairy tongue 1, 2
• Antipsychotic medications have also been associated with this condition 1

Lifestyle and Hygiene Factors

• Poor oral hygiene is a major contributing factor, allowing accumulation of debris and bacterial overgrowth 3, 1
• Smoking and alcohol use are commonly implicated 1, 2
• Soft diet contributes by reducing mechanical cleaning of the tongue surface 3, 1
• Use of mouthwashes has been associated with black hairy tongue 2

Medical Conditions

Immunosuppression

• Immunocompromised patients are at increased risk for developing black hairy tongue 1
• Patients with medical conditions limiting their ability to practice good oral hygiene are predisposed 1

Autoimmune Disease (Rare Association)

• Rhupus syndrome (overlap of systemic lupus erythematosus and rheumatoid arthritis) has been reported in association with black tongue, though this is an extremely rare presentation 3

Special Population: Infants

• Black hairy tongue is extremely rare in newborns and infants, though cases have been documented in infants as young as 3 months 6
• In one reported case, vitamin C supplementation was identified as a potential contributing factor 6

Critical Diagnostic Pitfall

• Black tongue must be distinguished from other serious oral pathology: Any persistent oral lesion, red/white patch, or non-healing ulcer lasting beyond 2-3 weeks requires immediate biopsy and specialist referral to exclude squamous cell carcinoma 7
• However, black hairy tongue has characteristic elongated papillae that differentiate it from malignant lesions 1, 2

Management Approach

• Treatment consists of gentle brushing or scraping of the tongue with a soft toothbrush 1, 2
• Elimination of predisposing factors (discontinue causative medications when possible, improve oral hygiene, cease smoking) 1, 2
• Prior application of 40% urea solution can enhance mechanical removal 2
• Topical tretinoin has been reported as an effective treatment option 2
• Prognosis is excellent with appropriate intervention, and the condition typically resolves within weeks 1, 6