Hairy tongue can be black in color. But your tongue can also go dark after you take an antacid with an ingredient called bismuth. For some people, it stains the tongue black when it mixes with saliva. It’s harmless and goes away once you stop taking the medicine.
Bright Red Tongue
A strawberry-red tongue could be an early sign of Kawasaki disease, a rare, serious illness that inflames blood vessels all over the body, most often in children. It’s also a symptom of scarlet fever. If your red tongue is also smooth and you have pain in your mouth, it might be a sign that your body doesn’t have enough vitamin B3.
If your tongue feels like you scalded it with hot coffee and tastes metallic or bitter, you may have burning mouth syndrome. It might mean a problem with the nerves in your tongue. Some health problems, like dry mouth, infections, acid reflux, and diabetes may cause it, too. For some people, acidic foods like pineapple as well as toothpaste, mouthwash, candy, or gum also make their mouth burn.