Why is my tongue green?

Green is not a color the tongue tissue turns on its own. When a tongue looks green, the color is almost always in a layer on the surface: a coating of dead cells, food debris and bacteria caught between the papillae, or a stain from something you ate or drank.

Cleveland Clinic groups green tongue with yellow tongue: both usually result from bacterial buildup. The difference is mostly which bacteria are growing and what has stained the film. DermNet notes that in hairy tongue, bacteria and yeasts overgrowing on lengthened papillae produce colored compounds (porphyrins), and that, while hairy tongue is usually brown or black, yellow and green forms are reported too.

Food and drink dyes

Green or blue candy, sports drinks, frosting, freezer pops and colored cereals can tint the coating within minutes. MedlinePlus lists dyes in food and medicines among the things that can contribute to hairy tongue. A dye stain is the easiest cause to spot: it appears right after eating, is often brightest at the center of the tongue, and fades over a few hours with eating, drinking and brushing.

Bacterial coating

If the green builds up over days and is accompanied by a stale taste or bad breath, a thick coating is the likely cause. Things that let it build include skipping tongue cleaning, a soft diet, dry mouth, mouth breathing and dehydration.

Green hairy tongue

Papillae that shed too slowly can grow long and look furry. Cleveland Clinic says black hairy tongue can also appear green, tan, yellow or white. The furry texture, usually toward the middle and back of the tongue, separates this from a flat stain.

Smoking and medicines

Tobacco stains the coating and dries the mouth. Antibiotics are a frequent trigger because they change the balance of bacteria and yeast; Cleveland Clinic lists antibiotics and antidepressants among medicines linked to hairy tongue.

After an illness

A fever, a cold or a stomach bug often means less eating, less drinking and more mouth breathing, all of which let a thick coating form. It may look yellow-green until you are eating and drinking normally again.

• Clean the tongue daily. A tongue scraper or soft toothbrush, pulled from back to front with light pressure, removes the coating where the green pigment sits. See how to use a tongue scraper.
• Brush and floss twice a day, and rinse with water after colored drinks.
• Drink more water, and treat a blocked nose if you have been mouth breathing.
• Stop or cut back on tobacco.
• Use a plain, alcohol-free mouthwash rather than peroxide-based rinses, which are linked to hairy tongue.

If you recently finished antibiotics, the coating may take a little longer to settle as normal mouth bacteria recover. Keep cleaning daily.

If home cleaning has not worked after two weeks, a dentist can confirm whether this is hairy tongue, a stubborn coating or something else. Cleveland Clinic notes that persistent hairy tongue may be treated with antibiotics or antifungals for an overgrowth, or a retinoid, and that a medicine causing it may be changed, but only with the prescriber's approval. Patches that leave raw, red areas that may bleed when wiped are more like oral thrush, as the NHS describes it, which needs antifungal treatment rather than more scraping.

See a dentist if a green tongue lasts more than two weeks despite daily cleaning, or straight away if it hurts, bleeds, or comes with white patches that leave sore red areas when wiped. People with a weakened immune system, diabetes, or who use asthma inhalers should get any persistent coating checked sooner, since these raise the risk of oral thrush according to the NHS.