Drug-Induced Black Hairy Tongue

Dennis F. Thompson, Pharm.D. FASHP, FCCP; Tiffany L. Kessler, Pharm.D.


Pharmacotherapy. 2010;30(6):585-593. 

In This Article

Abstract and Introduction


Black hairy tongue (BHT) is a benign, self-limiting disorder characterized by abnormally hypertrophied and elongated filiform papillae on the surface of the tongue. The prevalence of BHT is quite variable, ranging from 0–53.8% depending on the population. Many predisposing factors to BHT exist, and several drugs and drug classes have been implicated in causing this disorder. A modified Naranjo adverse drug reaction probability nomogram specific for BHT was used to rate causality for the available published case reports of drug-induced BHT. From the available data, antibiotics and drugs capable of inducing xerostomia are the drug classes that have modest evidence of causality and a rational mechanism. The presence of underlying predisposing factors in these cases along with the variable prevalence of BHT make drawing firm conclusions difficult. Treatment for BHT involves eliminating any predisposing issues and practicing scrupulous oral hygiene. Drug therapy and physical removal of the elongated filiform papillae are available for resistant cases. Clinicians should be aware of the prevalence, the predisposing factors and drug classes that may play a role in the development, and the treatment of BHT.


Black hairy tongue (BHT) is a benign, self-limiting disorder characterized by abnormally hypertrophied and elongated filiform papillae on the surface of the tongue (Figure 1).[1–3] Although it is usually asymptomatic, occasionally patients experience a tickling sensation in their mouth and, in more severe cases, a gagging reaction. This disorder is classically described as having a black discoloration; however, brown, yellow, and green discolorations have also been reported. Black hairy tongue is caused by defective desquamation of the dorsal surface of the tongue, usually in the posterior one third. This defective desquamation prevents normal debridement, resulting in excessive growth and thickening of the filiform papillae that then collect debris, bacteria, fungus, or other foreign materials. This accumulated foreign material usually contributes to the discoloration and can result in taste alterations, nausea, halitosis, and pain or burning of the tongue.[2–6]

Figure 1.

Black hairy tongue. (From reference 3 with permission.)

Black hairy tongue has an extensive history in the medical literature. Amatus Lusitanus has been credited with the first description of BHT in 1557.[7] Lusitanus described a patient with hairs on his tongue, which when "pulled out would renew themselves." From its discovery in 1557 until today, there has been a small but steady flow of interest and medical literature dealing with BHT, much of it occurring between 1930 and 1970,[4,7–18] although interest continues to be strong.[1–3,5,6,19–23] There are numerous synonyms for BHT, such as hyperkeratosis of the tongue, lingua villosa nigra, nigrities linguae, keratomycosis lingual, lingua villosa, and melanotrichia lingual.[6,7,18]

The prevalence of BHT in the general population is quite variable (Table 1).[6,24–27] Rates of BHT range from 0% in South African outpatients with diabetes mellitus[6] to 53.8% in Turkish dental patients who are heavy smokers.[25] It is difficult to conclude too much from these prevalence studies; however, these data do reinforce some of the factors that can aggravate, precipitate, and even cause BHT.These factors include the following:[4,6,18,25,27,28]

  • Tobacco (smoking, chewing)

  • Alcohol

  • Chronic dry mouth (xerostomia)

  • Poor oral hygiene

  • Drugs of abuse (particularly smoking drugs such as crack cocaine)

  • Oxidizing mouthwashes (sodium peroxide, hydrogen peroxide)

  • Recent radiation therapy

  • Trigeminal neuralgia

  • Cancer

  • Acquired immunodeficiency syndrome

  • Drugs associated with black hairy tongue (antibiotics and drugs capable of causing xerostomia)

Male subjects seem to exhibit a greater prevalence of BHT than do female subjects, and smoking, in a somewhat dose-dependent fashion, increases the prevalence of BHT.[25–27] Combinations of these factors are also likely to increase the chances of developing this disorder.

The diagnosis of BHT is simple. The cardinal sign is the presence of elongated, hypertrophied filiform papillae, which usually present as black but, as previously stated, can be other colors. This disorder can often be verified by visual observation, but microscopic examination is useful. History is key to identifying the presence of any aggravating factors. It is extremely important to clearly differentiate BHT from a discolored tongue. The presence of a black-stained tongue, by itself, does not fit the criteria for the diagnosis of BHT. A wide variety of drugs and chemicals can stain the tongue without producing the long, thick filiform papillae required for the diagnosis of BHT.[29–39] Minocycline and bismuth subsalicylate are relatively common causes of a black tongue but not necessarily BHT.[38,40–42]

A number of factors have been investigated as etiologic in BHT. Several studies have reported acidic pH readings in the saliva of patients with BHT.[7,18] Saliva pH readings from patients without BHT tend to be neutral to alkaline. Interpreting these facts is difficult because it is not clear if an acidic oral pH contributes to the etiology of BHT or is a consequence of BHT.[4] A number of investigators have studied the relationship between bacteria and fungi and BHT;[43–45] however, no conclusive evidence implicates any specific bacteria or fungi as etiologic in the pathogenesis of BHT. One early study explored nicotinic acid deficiency as a cause of BHT,[13] although no further work has been done in this area.

To provide a comprehensive evaluation of drug-induced BHT, we analyzed information obtained from a thorough search of the literature on this disorder.


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