Black Hairy Tongue

by Dr. Christopher Chang, last modified on 11/23/22.

Black hairy tongue is a relatively rare acquired condition that is considered harmless and self-limited. It is positively correlated with increasing age though there are cases reported in patients as young as 2 weeks old. Although "black" hairy tongue is typically described as a thickened area of black discoloration on the dorsal surface of the tongue with the sides and tip being unaffected, the black color descriptor is not universal. The color can also be white (see picture below), brown, and even blue. Generally, having a black hairy tongue causes no other symptoms and treatment is pursued due to aesthetic reasons. However, in rare cases, additional symptoms are present beyond the appearance itself and may include globus, burning, gagging, bad breath, and/or taste alterations. (Image on right from Wikipedia.)

So what exactly is going on when a black hairy tongue develops?

Anatomically, the tongue mucosa is normally covered by tiny taste buds classified as filiform, fungiform, foliate, and circumvallate papillae (watch video showing microscopic appearance of a normal tongue). The filiform papillae most densely covers the dorsal tongue and is the papillae that is most affected by black hairy tongue. Normally, the filiform papillae are small protrusions of the tongue mucosa, typically rising less than 1mm from the surface. Along with taste, they function to increase friction between the tongue and food in order to move particles around within the oral cavity. However, in black hairy tongue, these normally <1mm tongue protrusions can grow to over 1cm in length and 2mm width. When these elongated protrusions are examined under the microscope, the “hairs” are actually highly elongated cornified spines that result from delayed desquamation of the cells in the central column of filiform papillae and marked retention of secondary papillary cells that express hair-type keratins. To use an analogy, think of a skinny tower of lego blocks. Normally, after making a lego tower about 5 pieces high, each subsequent piece will fall off due to instability. With black hair tongue, this skinny lego tower is growing to 10 or 15 pieces high with subsequent pieces being added not easily falling off like it normally should.

This carpet of abnormally long filiform papillae protrusions then secondarily collect fungi, bacteria, and inorganic particles which leads to the discoloration. To reiterate, micro-organisms found in black hairy tongue is coincidental and not causative. I will further stress that although fungi and bacteria may be present and do contribute to the discoloration, there is no "infection" present per se. These organisms are happily just living on the surface without actually invading the tongue lining. Treatment (if pursued) is really to address the long filiform papillae and not so much what's on it.

Causes

This condition may mysteriously appear and just as mysteriously disappear for no perceivable reason. However, sometimes this condition can occur due to a precipitating trigger which when corrected/avoided will often resolve the discoloration within weeks.

So, what are some of these triggers that might cause a black hairy tongue?

 

Medications (generally encompassing antibiotics and psychotropics) that have been reported to cause black hairy tongue are as follows:

Treatment

Treatment is geared towards FIRST avoiding any precipitating triggers and/or medications listed above as well as manual debridement. In particular, remind patients to avoid chemical mouthwash of any kind like listerine or scope as well as use a bland, SLS-free and fluoride-free toothpaste (ie, Tom's).

Additionally, it is recommended to practice great oral hygiene (a dental visit may be warranted) as well as scraping the tongue (ie, tongue scraper as shown in the image) in order to manually remove not just organisms and debris, but also to "cut" the abnormally long filiform papillae shorter down to a more normal small size. Some patients find using an electric toothbrush with stiff bristles work better.

If there is a heavy growth of thrush present, a course of prescription mycelex troches can help knock this back down, but again, will not correct this problem which is due to an anatomic elongation of the filiform papillae. Antibiotics should be avoided which may actually exacerbate this problem. To reiterate, there is no "infection" present. The organisms are coincidental and not causal.

Second-line treatments are anecdotal with no single treatment proven to reliably cure/reverse black hairy tongue. These include:

• Molecular Iodine Rinses (IoRinse) three times a day
• 1% Gentian Violet application to the tongue using a q-tip daily for 3 days
• Baking soda rinses (1/2 - 1 tsp of baking soda in 1 cup of water)
• 3% hydrogen peroxide rinses (although there are some anecdotal reports that this may trigger black hairy tongue)
• 50% trichloroacetic acid application *
• 40% urea solution application *
• Salicylic acid application *
• Topical and oral retinoids
• Vitamin B complex
• Thymol application *

One would brush the tongue with a toothbrush after above treatments (denoted by *) directly applied to the tongue.

If resolution is not forthcoming in spite of these interventions, a biopsy can be obtained to confirm nothing else is going on before proceeding to more invasive options including manually cutting the filiform papillae shorter with scissors, carbon dioxide laser, or electrodessication.

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