A black spot on your gums is almost always harmless. The most common cause is an amalgam tattoo, a tiny deposit of metal left behind from a dental filling, which affects about 3.3% of American adults. But dark spots can also come from natural pigmentation, smoking, minor injuries, medications, or (rarely) something that needs medical attention. Understanding what different spots look like helps you figure out whether yours needs a closer look.
Amalgam Tattoos: The Most Common Cause
If you’ve ever had a silver dental filling, there’s a good chance your dark spot is an amalgam tattoo. During filling placement or removal, tiny particles of the metal amalgam can become embedded in your gum tissue. The result is a flat, blue-gray or blue-black spot that shows up on the gums, inner cheek, or the ridge of bone where teeth sit. These spots range from a few millimeters to larger, more diffuse patches.
Amalgam tattoos don’t hurt, don’t grow, and don’t need treatment. Their borders can be sharp or somewhat blurry, which sometimes makes them tricky to distinguish from other pigmented spots just by looking. Your dentist can often confirm the diagnosis with an X-ray: larger deposits of amalgam show up as bright white spots on the image. If the spot appeared near a tooth that has (or once had) a silver filling, an amalgam tattoo is the most likely explanation.
Natural Pigmentation
People with darker skin tones often develop pigmentation on their gums that has nothing to do with disease. This is called physiologic pigmentation, and it results from melanocytes (the cells that give skin its color) being more active in the gum tissue. The pigmentation typically appears as flat, evenly colored patches ranging from light brown to nearly black. A key feature is that it’s usually symmetrical, showing up on both sides of the mouth, most often on the front-facing gums of the upper and lower jaw.
This type of pigmentation can be present from childhood or develop gradually. It doesn’t change suddenly in shape or color, and it requires no treatment.
Smoking and Tobacco Use
Long-term smoking stimulates melanin production in the gums, a condition sometimes called smoker’s melanosis. Research consistently shows that gum pigmentation is significantly more common in tobacco users than in non-users. The spots tend to appear on the gums facing the lips, particularly in the lower front area, and they’re usually flat, brown to black, and diffuse rather than sharply defined.
Smoker’s melanosis often fades gradually after quitting tobacco, though it can take months or longer. The pigmentation itself isn’t dangerous, but it’s worth noting that smoking independently raises the risk of oral cancers, so regular dental check-ups matter.
Bruises and Minor Trauma
A sudden dark spot that appeared after biting something hard, brushing aggressively, or having dental work done is likely a bruise (hematoma). Blood pools under the thin gum tissue and looks dark purple or black. The key distinction from other spots is timing: bruises appear quickly after an injury, often feel tender, and change color as they heal. Swelling and discomfort from dental procedures typically peak around 48 to 72 hours, and the discoloration fades within one to two weeks. If your dark spot showed up overnight or after trauma and is slowly lightening, it’s resolving on its own.
Medications That Darken Gums
Several types of medication can cause dark patches on the gums as a side effect. The most well-known culprits include:
- Antimalarials like hydroxychloroquine, which directly stimulate the pigment-producing cells in your mouth
- Certain antibiotics, especially minocycline and tetracycline, which can stain underlying bone in a way that’s visible through thin gum tissue
- Antiretroviral drugs used for HIV treatment, which cause gum darkening in roughly 23 to 26% of patients
- Oral contraceptives and hormone replacement therapy, which trigger increased melanin production indirectly through hormonal pathways
- Chlorhexidine mouthwash, a common prescription rinse that can cause surface staining
If you started a new medication in recent months and then noticed a dark spot on your gums, the timing is worth mentioning to your doctor or dentist. In many cases, the pigmentation fades after switching medications, though this depends on the drug and how long you’ve taken it.
Oral Melanotic Macules and Moles
An oral melanotic macule is a small, flat, well-defined brown or black spot caused by a localized increase in melanin. These are typically under 1 centimeter across and most commonly appear on the lower lip, though they can show up on the gums. They’re benign and usually stay the same size and color over time.
Moles can also occur inside the mouth. The most common type found on oral tissue is the intramucosal nevus, a small, stable bump or flat spot made of pigment-producing cells. Blue nevi, another benign type, sit deeper in the tissue and appear blue-black because of how the pigment filters through the overlying layers. Both types are uncommon in the mouth but harmless.
Systemic Health Conditions
In rare cases, dark spots on the gums are an early sign of a broader medical condition. Addison’s disease, a disorder where the adrenal glands don’t produce enough hormones, causes widespread darkening of the skin and mouth. Notably, pigmentation inside the mouth often appears before any skin changes. It typically affects the gums, tongue, inner cheeks, and lips, and it’s accompanied by other symptoms like fatigue, weakness, and salt cravings.
Peutz-Jeghers syndrome, a genetic condition, causes clusters of small dark spots around the lips and inside the mouth, usually appearing in childhood alongside intestinal problems. Both conditions involve pigmentation in multiple areas rather than a single isolated spot.
When a Dark Spot Could Be Serious
Oral melanoma is rare, accounting for roughly 0.2 to 8% of all melanomas, but it is serious. Unlike skin melanoma, which is often caught early, oral melanoma tends to be diagnosed later and has a much lower survival rate, with overall five-year survival around 15%.
The screening criteria used for skin moles (asymmetry, irregular borders, multiple colors, diameter over 6 millimeters, and changes over time) don’t translate perfectly to the mouth. Many benign oral spots share some of these features. That said, certain characteristics should prompt a dental visit sooner rather than later:
- Rapid growth over weeks or months
- Color changes, especially multiple shades of brown, black, and red within the same spot
- Irregular or ragged borders that are expanding
- A raised or lumpy texture in a spot that was previously flat
- Bleeding or ulceration without an obvious cause
Any unexplained pigmented spot in the mouth that you can’t attribute to a filling, medication, smoking, or natural pigmentation is worth having evaluated. A biopsy, where a small tissue sample is examined under a microscope, is the only definitive way to rule out melanoma. The procedure is straightforward and typically done in a dental or oral surgery office. Most biopsied spots turn out to be benign, but early detection makes an enormous difference for the small number that aren’t.