A black, purple or dark spot on the gums: when is it harmless, and when is a biopsy needed?

Dark-coloured areas inside the mouth fall into two main groups. The first is colours that come from melanin, the body's own dye: natural pigment, colour due to smoking, colour left after inflammation, colour caused by some medicines and hormone disorders, and a mole or melanoma arising from the melanin-producing cells themselves. The second is substances that enter the tissue from outside: the most common example is amalgam filling particles. One review divides the spots into those that stay at a single point and those that spread over a wide area; an amalgam tattoo and a mole are single-point, while natural pigment, smoker's melanosis, medicine-related colour and colour due to systemic diseases are in the widespread group.

Of 761 pigmented lesions inside the mouth examined in the 45-year records of two pathology services in Brazil, 53.6% were amalgam tattoos, 18.3% melanotic macules (a flat, well-defined brown spot), 10.8% natural (ethnic) pigment and 9.9% moles. Melanoma was rare at 2.1%. These rates come from lesions that were biopsied, which means they do not show the distribution of every dark spot you see in the population; because natural pigment and smoker's melanosis are usually recognised without the need for a biopsy, they appear less often in the list than they really are.

Natural pigment is the most common widespread colour. According to one review, it can range from dark brown to black, generally becomes noticeable in the first twenty years of life, can darken with age and sits mostly on the attached gum, while generally leaving the very edge of the gum free. A colour that has been there for years, runs like a band in a similar way on both sides of the gum and causes no raised area is most probably this.

Smoker's melanosis is a widespread, irregular darkening that forms when tobacco stimulates the pigment cells in the gum. The same review writes that it is seen most on the gum in the front region and the mucosa behind the lips, and that the colour gradually lightens when smoking is stopped. If you smoke and your lower or upper front gums have darkened over the years, this is the first thing that comes to mind. A smoking stain is staining on the surface of the tooth; smoker's melanosis, by contrast, is a change in the gum's own colour and does not come off with cleaning.

An amalgam tattoo forms when particles of old silver-coloured fillings become embedded in the tissue while the filling is being placed, polished or removed. According to DermNet, it is seen as a flat blue, black or slate-grey area and appears most often on the gum next to an amalgam filling; it can also be on the palate, cheek or tongue. It is harmless, causes no symptoms and requires no treatment. If it sits near a filling, an examination is generally enough; large particles can be seen on an X-ray, and if the diagnosis cannot be made with certainty, a biopsy is carried out. The spot can remain even if the filling was removed years ago or the tooth has been extracted.

A grey appearance at the edge of a crown is a separate matter. In metal-ceramic crowns the metal substructure extends right to the edge of the crown; if the gum is thin, the metal can show through it as a shadow, and if the gum recedes, the edge is exposed and a thin grey or black line appears at gum level. This is not a disease but a matter of appearance. If it is on a single crown, you can discuss replacing the crown with a metal-free option with your own dentist. If you see a similar shadow over an implant, we have covered this separately on the page where we explain the situations in which implant metal shows.

Medicines can darken the gums too. One review lists chloroquine and hydroxychloroquine, which are used in the treatment of malaria and rheumatic disease, some psychiatric medicines and some cancer medicines. In the case report of a patient taking minocycline for a skin problem, darkening of the colour of the gums, lips and nail beds developed months after the medicine was started and decreased markedly nine months after it was stopped. Do not stop the medicine yourself; consult the doctor who prescribed it.

Adrenal insufficiency (Addison's disease) is a rare cause, but one that must not be missed. MSD Manuals writes that in this disease a bluish-black discolouration can develop on the lips and around the mouth, that the person is weak and tired and gets dizzy on standing up, and that there may be weight loss, loss of appetite, nausea and vomiting. According to the review, widespread brown spots that can affect all surfaces are seen in the mouth. If new darkening on your gums comes with general symptoms of this kind, the assessment is carried out by a GP (family doctor).

Melanoma is rare inside the mouth, but serious. In a systematic review bringing together 2,230 cases, the most common sites were the hard palate and the gums, the mean age at diagnosis was 58.2, most patients had been diagnosed at an advanced stage and 5-year survival was 33.1%. DermNet writes that melanoma inside the mouth can appear as a discolouration in the mouth or as a painless, bleeding lump or ulcer; it also adds that mucosal melanomas can often be unpigmented, that is, they do not always look black. The fact that it causes no pain in the early period and sits in places out of sight contributes to it being noticed late. That is why a single spot on the gums that has newly appeared or is changing is not monitored; it is shown to a dentist.

The features in the first list suggest a harmless picture; those in the second suggest a picture that may require a biopsy or further assessment. The definite distinction is made by a clinician.

A dark spot on the gums is rarely an emergency. The order below shows first the emergency signs, then what you can do at home, then what the dentist does.

1. 1

   Look at your general condition first

   If, in someone who has been diagnosed with Addison's disease or is suspected of having it, the symptoms suddenly get worse and a fast heartbeat, severe dizziness, severe pain in the abdomen or flank, vomiting, extreme drowsiness or confusion, seizures or loss of consciousness are added, the NHS regards this as an adrenal crisis and asks for emergency help to be called; call 112. A spot on the gums is not an emergency on its own.

2. 2

   Take a photograph of the spot

   In good light, pull your lip down or up and photograph the spot and the teeth next to it together. Let a whole tooth be in the photograph to give scale. Note the date and repeat from the same angle once a month. This is the most reliable way to see growth and colour change.

3. 3

   Work out the history of the spot

   How long has the spot been there, does it show in your old photographs, is there an old silver filling or a metal-ceramic crown right next to it, was a tooth extracted there, do you smoke, have you started a new medicine in the past year? The answers to these questions usually narrow the diagnosis down considerably.

4. 4

   Look at the rest of the mouth and the body

   Is there a similar colour on your lips, inside your cheeks, on the palate and on your nails too? Widespread darkening seen in many places at once suggests medicines, smoking and systemic diseases; a spot at a single point, on the other hand, suggests amalgam, a mole or, more rarely, melanoma.

5. 5

   Examination and X-ray at the dentist

   The dentist looks at the border of the spot, its colour, whether it is raised and the filling or crown around it. If an amalgam tattoo is suspected, an X-ray can show the particle. DermNet writes that with a typical amalgam tattoo next to a filling, an examination is usually enough.

6. 6

   Biopsy if needed

   For spots where the diagnosis cannot be made with certainty, or that are new, changing, irregular at the edge or multicoloured, a small tissue sample is taken under local anaesthetic. The reviews emphasise that most pigmented lesions inside the mouth are benign, but that when necessary the definite diagnosis is made by biopsy.

7. 7

   General tests and referral if needed

   If the widespread darkening comes with weakness, weight loss or dizziness, the dentist refers you to a GP (family doctor) or to endocrinology. MSD writes that in Addison's disease cortisol and ACTH levels are measured.

The treatment of a dark spot depends entirely on its cause; usually no treatment at all is needed.

The following are decisions that waste time or money with this complaint.

With dark spots it is not healing that is monitored but whether the spot changes. The sequence below is a practical monitoring plan.

1. Today

   Take the photograph, and note the date and the history of the spot. If it is a single new spot, book an appointment without waiting.

2. Once a month

   Take a new photograph in the same light and from the same angle and compare it with the previous one. Look for changes in size, colour and edge.

3. At every dental check-up

   Show even a spot you have been told is harmless at check-ups; the dentist can enter it in the record and compare.

4. The months and years after stopping smoking

   In smoker's melanosis the colour is expected to lighten gradually. An area that does not lighten, or that darkens at a single point, should be reassessed.

5. After a change of medicine

   In the minocycline case, the colour had decreased markedly nine months after the medicine was stopped. Medicine-related colour changes slowly over months.

Because most dark spots on the gums do not require treatment, the cost is mostly about clarifying the diagnosis and, if wanted, improving the appearance. The items that determine the extent:

Examination and X-ray

Diagnoses such as an amalgam tattoo are usually made by examination and X-ray.

Biopsy and pathology

With a suspicious spot, taking the tissue sample and having it examined in pathology are separate items.

Cosmetic procedure

Lightening the colour by laser or replacing a metal-ceramic crown with a metal-free crown are optional cosmetic items; with laser, repeat sessions may be needed.

The underlying condition

If a hormone-related or medicine-related cause is found, the tests and follow-up proceed outside dentistry, in the relevant department.