Sour Taste in Mouth: Causes, Sudden Onset and What Helps

The valve between the food pipe and the stomach sometimes lets acid and partly digested food come back up. You may feel heartburn, or you may only notice a sour or acidic taste at the back of the tongue, a sore throat or a morning cough. Acid at the back of the throat also bothers the teeth, so reflux is something dentists see.

Reflux is more likely after heavy, spicy or fried meals, with large portions, when lying down soon after eating, with obesity and in pregnancy. Tea, coffee, smoking and tobacco can make it worse. Our page on bad breath and our guide on bad breath from the stomach explain how reflux can add to a smell as well as a taste.

A taste that appears suddenly is often tied to something specific: a large or late meal, a spell of acidity, a new medicine or supplement, or a cold or sinus infection. Often it passes within hours or days.

A sudden sour taste that keeps recurring, or that comes with chest pain, trouble swallowing, vomiting or black stools, needs a doctor rather than home care. Chest pain, especially with sweating or breathlessness, needs emergency care and is not something to put down to acidity.

A coated tongue, plaque along the gum line, gum disease and a decayed tooth all produce sour or stale tastes as bacteria ferment food debris. Dry mouth makes the taste more noticeable, because there is less saliva to wash it away. Our page on dry mouth explains why saliva matters and what reduces it.

Frequent acid in the mouth, from reflux or from sour drinks and sweets, can also wear the enamel. If you have a sour taste and teeth that are becoming sensitive or thin at the edges, mention the reflux to your dentist.

Eat smaller meals, leave a gap of a few hours between dinner and lying down, raise the head of the bed, and cut back on spicy, fried and very acidic food. Avoid tobacco in any form. Rinse with plain water after a reflux episode and wait before brushing, because acid-softened enamel brushes away more easily.

Keep up the basics: brush twice a day, clean between the teeth, clean the tongue and sip water through the day. If the taste is more bitter than sour, our guide on bitter taste in the mouth covers the overlap.

See a doctor if the sour taste happens most weeks, wakes you at night, or comes with trouble swallowing, vomiting, weight loss or a cough that will not clear. See a dentist if the mouth is sore, the gums bleed or a tooth hurts.