Why do I have a sour taste in my mouth?

Sour taste receptors on the tongue respond to acid. That is why stomach acid reaching the back of the throat produces such a distinct sour taste, and why the NHS lists "an unpleasant sour taste in your mouth, caused by stomach acid" as one of the two main symptoms of acid reflux, alongside heartburn. When there is no acid present, a sour taste can still come from a dry mouth, bacteria or a change in how taste signals are processed.

1. Acid reflux or GERD. The muscle between the esophagus and stomach does not close fully, so acid rises. The NHS notes symptoms are often worse after eating, when lying down and when bending over.
2. Dehydration. A dry mouth alters taste.
3. Smoking. Dulls taste and often leaves a sour aftertaste.
4. Poor oral hygiene. Plaque and bacteria on teeth and tongue produce unpleasant tastes.
5. Infections. Colds and sinus infections change taste, and oral thrush, a yeast infection, can cause a sour or unpleasant taste with white patches.
6. Medicines. Cleveland Clinic names antibiotics, antipsychotics, chemotherapy and over-the-counter antihistamines.
7. Mouth breathing and aging. Both dry the mouth and reduce taste sensitivity.
8. Other conditions. Occasionally diabetes, liver disease, kidney disease, anxiety, zinc deficiency, or hormone changes in pregnancy and menopause.

Reflux is likely if the sour taste comes with any of these: a burning feeling in the middle of the chest, sour liquid rising into the throat, a cough or hiccups that keep returning, a hoarse voice, bad breath, bloating or nausea. A sour taste that is worst in the morning, after big meals or when you bend down also fits. Reflux is common in pregnancy, and a pharmacist can advise which remedies are suitable.

If none of those fit, and especially if your tongue has a white coating that does not scrape off or your mouth is sore, thrush or another oral cause is more likely.

• For reflux, the NHS recommends smaller, more frequent meals, not eating within 3 or 4 hours of bed, raising the head of the bed by 10 to 20 cm, avoiding tight clothing around the waist, cutting back on alcohol and identifying trigger foods.
• Drink enough water; Cleveland Clinic suggests aiming for around eight glasses a day unless you have been told to limit fluids.
• Brush twice and floss once a day, and clean your tongue. Check it for white patches that could be thrush.
• Stop smoking, which helps taste, breath and gums at the same time.
• Do not stop a prescription because of taste; ask the prescriber about alternatives or ways to cope.

Cleveland Clinic advises getting checked if heartburn or reflux happens at least twice a week over several weeks, since this may be GERD, and if a sour taste lasts for weeks, especially with weight loss, fatigue or just feeling off. The NHS adds food getting stuck in your throat, frequent vomiting and unintended weight loss as reasons to see a GP. A doctor may prescribe acid-reducing medicine and, if symptoms persist, refer you for tests.