Black spots on the tongue are almost always harmless. The most common causes are a buildup of dead cells on the tongue’s surface, a reaction to something you ate or drank, or natural pigmentation that you’re only now noticing. In rare cases, a dark spot can signal something that needs medical attention, so it’s worth understanding what each cause looks like.
Black Hairy Tongue
The most frequent cause of widespread black discoloration is a condition called black hairy tongue. Despite the alarming name, it’s temporary and not dangerous. Your tongue is covered in tiny projections called papillae, which normally shed as they grow. When they don’t shed properly, they elongate and trap bacteria, yeast, food particles, and dead cells. This buildup darkens over time, and the overgrown papillae can give the tongue a furry or “hairy” appearance.
Black hairy tongue affects roughly 1 to 11 percent of the population, depending on the region studied. Men are about three times more likely to develop it than women, and prevalence climbs with age, reaching nearly 40 percent in people over 60 in some studies. You’re at higher risk if you smoke, drink a lot of black tea or coffee, have poor oral hygiene, or are taking antibiotics. Antibiotics can shift the balance of bacteria in your mouth, letting certain pigment-producing organisms overgrow.
The fix is straightforward: brush your tongue gently twice a day with a soft-bristled toothbrush or a flexible tongue scraper. If you smoke, cutting back will help. If antibiotics triggered the change, it typically resolves on its own once you finish the course. Black hairy tongue rarely needs medical treatment and is generally short-lived.
Pepto-Bismol and Similar Medications
If the black discoloration appeared suddenly and you recently took an antacid containing bismuth (the active ingredient in Pepto-Bismol), that’s likely your answer. Bismuth reacts with small amounts of sulfur naturally present in your saliva to form bismuth sulfide, a harmless black compound. This can coat your tongue, teeth, and even darken your stool.
The discoloration is temporary. It fades on its own within a few days after you stop taking the medication, though brushing your tongue can speed things along.
Natural Pigmentation
Flat, dark spots that have been present for a long time and haven’t changed in size or shape are often just normal pigmentation. People with darker skin tones are more likely to have melanin deposits on the tongue, gums, and inner cheeks. These spots are painless, uniform in color, and stay the same over months and years. They don’t require any treatment.
Hyperpigmentation From Systemic Conditions
Certain medical conditions can cause new dark patches to appear inside the mouth. Addison’s disease, a condition where the adrenal glands don’t produce enough hormones, is the most well-known example. The hormonal imbalance triggers excess melanin production, leading to brown or dark patches on the gums, lips, inner cheeks, and tongue. These oral changes sometimes appear before other symptoms like fatigue, weight loss, and low blood pressure, making them a potentially early clue.
Other conditions that can cause oral hyperpigmentation include Peutz-Jeghers syndrome (which also causes spots on the lips and fingers) and certain vitamin deficiencies. If dark spots appeared recently and you’re also experiencing unexplained fatigue, dizziness, or changes in skin color, it’s worth bringing up with your doctor.
When a Dark Spot Needs Attention
Oral melanoma is rare, but it does occur. The same ABCDE guidelines used for evaluating moles on the skin can help you assess a spot on your tongue: asymmetry, irregular borders, color variation within the spot, a diameter larger than 6 millimeters (about the size of a pencil eraser), and evolution or change over time. A spot that is growing, changing color, bleeding, or developing uneven edges is the kind that warrants prompt evaluation.
A general rule used in clinical practice: any oral lesion that doesn’t resolve within three weeks should be examined by a dentist or specialist. This doesn’t mean every spot that lasts three weeks is dangerous, but it’s a reasonable threshold for getting a professional opinion.
Staining From Food and Drinks
Sometimes the explanation is simpler than any medical condition. Dark berries (blueberries, blackberries), black licorice, red wine, coffee, and certain candies or food dyes can temporarily stain the papillae on your tongue. If you noticed the spots after eating or drinking something deeply colored, try brushing your tongue and waiting a day. If the discoloration clears, that’s all it was.
What to Do Next
Start with the basics. Brush your tongue gently twice a day, stay hydrated, and think about whether anything has changed recently: a new medication, a course of antibiotics, a shift in diet, or an increase in smoking or coffee intake. Most black spots on the tongue resolve within days to weeks once the underlying cause is addressed.
If the spots are flat, painless, and have been there unchanged for years, they’re almost certainly normal pigmentation. If a spot is new, growing, irregularly shaped, or accompanied by other symptoms you can’t explain, have a dentist or doctor take a look.