What does this mean?
The papillae on the top of the tongue renew themselves constantly; their tips wear down and shed, and new ones come through underneath. When this cycle slows, the papillae do not shed and they grow longer. As the lengthened structures lean against one another, the surface comes to look hairy, like the pile of a carpet. The colour comes from bacteria settling between the papillae and from staining substances taken in from outside; brown, yellowish, greenish or near-black shades can be seen.
What separates this from an ordinary coating is that what you see is not a layer lying on the surface but the overgrown tissue itself. A coating comes partly away when it is wiped gently and pink surface shows underneath; overgrown papillae are not cleaned off in one go, but shorten slowly over days with regular care. The appearance usually gathers in the middle and towards the back of the tongue, while the tip and the edges stay normal. The change is superficial; movement of the tongue is generally unaffected, though some people report gagging and a change in taste.
This appearance has been reported more often with tobacco use, with strong tea and coffee, with a dry mouth and during periods when mouth care has slipped. It can also be seen after chlorhexidine mouthwashes, stomach medicines containing bismuth and some courses of antibiotics. A soft diet and little chewing can keep the picture going, because they reduce the mechanical wear on the papillae. Once the cause is removed, it is expected to settle in most people.
Darkening of the tongue is usually explained by a slowing of surface renewal and by colour clinging to these overgrown structures. The headings below bring together the causes that most often accompany this change.
Likely causes
What helps at home?
- Clean your tongue gently twice a day, from the back towards the front, with a soft brush or a tongue cleaner; the appearance may take a few days to improve.
- Try cutting back on tobacco, strong tea and coffee; these are the factors reported most often in staining.
- Do not carry on with a chlorhexidine mouthwash for weeks on end unless your dentist has advised it.
- Make room during the day for foods that need chewing; that keeps the natural wear on the surface going.
- If the colour change is spreading to the cheeks, the palate or the inside of the lip.
- If difficulty swallowing, pain or a temperature goes with the appearance.
- If the darkening has gathered at a single spot, has sharp borders and is raised.
- If the appearance has not receded at all despite several weeks of regular cleaning.
- If you are having treatment that suppresses your immune system.
Frequently asked questions
- Will this appearance be permanent?
- In most people it is not permanent. Once the staining factor is reduced and the surface is cleaned regularly, the papillae are expected to shorten; that can take a few weeks. As long as the cause carries on, it is usual for the appearance to come back.
- Is a near-black tongue the sign of a serious illness?
- Alarming though it looks, this change is regarded as superficial and is most of the time not linked to serious illness. Even so, a picture that spreads inside the mouth, is painful, or comes with a temperature or difficulty swallowing should be assessed for other causes.
- It appeared after I took antibiotics; should I stop the medicine?
- Do not stop a prescribed medicine on your own decision. This change has been reported after some courses of medicine; the sensible step is to speak to the doctor who prescribed it, tell them what has happened and leave the decision to them.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.