Bad Taste in Your Mouth: What Causes It

By the team at Bollington Dental Practice, under the clinical direction of Dr Ellie Burrows, Principal Dentist. Updated August 2026.

A persistent taste you cannot rinse away is one of those symptoms people put up with for months. It is usually dental, it is usually straightforward to find, and the specific flavour is a genuine clue.

The short answer

Most persistent bad tastes come from somewhere in the mouth: an infected or dying tooth, gum disease, a food trap, or a failing filling. Metallic tastes are the exception and are more often caused by medication, reflux or a mineral imbalance than by teeth. If a taste has lasted more than a couple of weeks and brushing does not shift it, something is producing it and it is worth finding.

A taste that will not shift? A persistent bad taste usually has a findable cause, and an examination (£89 for new patients, including X-rays) is the quickest way to rule infection in or out. If there is pain or swelling too, see our emergency page.

What the taste tends to tell you

• Foul, salty or like pus. This usually means infection. A dental abscess, an infected gum pocket, or a dying nerve in a tooth. It often comes and goes as an abscess partly drains, which is why people wrongly think it is resolving. See our guide to dental abscess.
• Persistently unpleasant with bleeding gums. Gum disease, where inflamed pockets around the teeth harbour the bacteria producing it. Covered fully in bleeding gums and gum disease.
• Metallic. Frequently medication, and a long list of drugs do it, including some antibiotics, blood pressure medicines and metformin. Also iron or zinc supplements, acid reflux, pregnancy, and occasionally a vitamin B12 or zinc deficiency. Rarely, an old amalgam filling touching a different metal restoration.
• Sour or acidic, especially waking up. Acid reflux. Worth taking seriously because stomach acid erodes enamel from the inside of the teeth backwards, and we can often see that pattern before you feel it.
• Stale and worst in the morning only. Normal. Saliva drops overnight. If it clears after brushing, that is nothing.
• Bad taste with something stuck. A food trap between teeth, under a bridge, or in the gum flap over a partly erupted wisdom tooth. Tiny cause, disproportionate smell.
• Bitter, with a recent filling or crown. Sometimes a temporary cement or a high restoration trapping food. Easy to adjust, so mention it rather than waiting.

When to get seen promptly

Ring the same day if a foul taste comes with facial swelling, throbbing pain, a raised temperature, or a bad taste that floods suddenly, which usually means an abscess has discharged. Go to A&E if swelling is spreading towards your eye or down your neck, or if swallowing or breathing is becoming difficult.

Separately, and importantly: an altered taste alongside an ulcer, patch or lump in the mouth that has been there more than three weeks should be checked, which is covered in our guide to mouth cancer signs. That is a small risk, not a likely one, but three weeks is the point at which you stop waiting.

What helps in the meantime

• Clean the back of your tongue daily. It holds more odour-producing bacteria than your teeth do.
• Clean between every tooth once a day, which is where food traps and gum pockets live.
• Drink more water. A dry mouth concentrates everything, and see our guide to dry mouth if that is your main problem.
• Rinse with warm salty water if a gum is sore, but do not rely on it.
• Avoid masking it with strong mouthwash before your appointment, because we would rather assess it as it is.

What it costs to find the cause

A new patient examination is £89 including X-rays, or £60 for existing patients. X-rays matter here, because an abscess or decay under a filling is often invisible from above. Treatment then depends entirely on what we find: a filling from £125, root canal treatment from £305, a hygiene appointment from £60, or an extraction from £126. Everything is on our fees page.

In pain right now? Our two-minute urgency checker tells you honestly whether this is a call-us-today problem or one that can wait, with practical advice in the meantime.

Frequently asked questions

Why does my mouth taste metallic?

Medication is the most common cause by a distance, so check the leaflet for anything you have started recently. Supplements, reflux, pregnancy and occasionally a nutritional deficiency account for most of the rest. It is much less often a dental problem than the other tastes on this page.

Can a bad taste come from one tooth?

Very much so, and it is one of the commonest scenarios. A single dying nerve, a cracked filling holding stagnant food, or one deep gum pocket can produce a taste you notice constantly. Which is also why it usually disappears completely once treated.

Will mouthwash get rid of it?

Only briefly, and an alcohol-based one can make things worse by drying your mouth. If the cause is infection or a food trap, no rinse will reach it.

It comes and goes. Does that mean it is not serious?

No, and this is the trap. A chronic abscess discharges intermittently, so the taste floods and then eases while the infection carries on underneath. Intermittent is not the same as improving.

If a taste has outstayed a fortnight, let us find out why. Call us on 01625 574609.

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