What causes purple spots on the tongue?

• Under the tongue or along its lower sides: most often normal veins. The lining here is thin and see-through, so blood vessels show as blue-purple lines or beads.
• On top of the tongue: more likely a blood blister, a bruise, a stain or, occasionally, small bleeds.
• Spread across the mouth: pinpoint purple dots on the tongue, cheeks and palate together suggest petechiae, which need a blood test.

A simple check a dentist uses: pressing a clear glass slide on a vascular spot makes it blanch (go pale) because the blood is pushed out of the vessel. Bleeding under the surface, like petechiae and bruises, does not blanch.

Sublingual varices

These are dilated veins under the tongue that look like raised blue-purple beads or wiggly lines. A 2025 meta-analysis in PMC puts their prevalence at around 30%, rising with age. They are harmless and usually need no treatment. The same analysis found they are more common in people with high blood pressure, heart disease, a smoking history or dentures, so a dentist may suggest a blood pressure check, but the veins themselves do not cause problems.

Blood blister or bruise

Biting the tongue, a hot food burn or dental work can trap blood under the surface, creating a dark purple bubble or patch. It usually fades within one to two weeks. Do not pop it.

Food and drink stain

Blueberries, blackberries, beetroot, red wine and some candies can tint the tongue purple. A stain is spread across the surface rather than a defined spot and fades within hours or after cleaning the tongue.

Petechiae and purpura

Petechiae are pinpoint red-purple dots from tiny bleeds; purpura are larger purple patches. A review in PMC of the oral signs of low platelet counts describes petechiae, bruising and blood blisters in the mouth, including on the top of the tongue, with spontaneous gum bleeding often an early sign. Low platelets can come from infections, medicines, immune conditions or blood disorders, so these spots need a blood count rather than a wait-and-see approach.

Hemangioma and vascular malformations

These are clusters of blood vessels that form a soft red to bluish-purple swelling. Case reports in PMC note they are relatively uncommon on the tongue, may blanch with pressure, and are investigated with ultrasound or MRI before any treatment.

Kaposi sarcoma

The American Cancer Society describes Kaposi sarcoma lesions as purple, red or brown spots; in the mouth they are usually flat at first. It is far more likely in people with HIV or a weakened immune system, and is confirmed by biopsy.

• If you have just noticed veins under your tongue, look in a mirror at both sides. Symmetrical, long-standing veins are almost always normal anatomy.
• For a blood blister, avoid hot, crunchy and spicy food for a few days and let it resolve on its own.
• Take a dated photo of any unexplained purple spot so you can tell whether it is changing.
• If you take blood thinners, mention any new purple spots or bleeding in your mouth to your prescriber.

Examination, sometimes with the glass-pressure test, sorts most purple spots quickly. If petechiae are suspected, a complete blood count checks platelet numbers. A persistent purple lump may be imaged with ultrasound or MRI and, if needed, biopsied. Harmless varices and healed blisters need no treatment.