Why does my breath smell like vinegar?

Vinegar is acetic acid, and people use "vinegar" for any sharp, sour, acidic smell. The evidence on this exact description is thin: the references we checked describe breath as sour, fruity, fishy or sulfurous, but not specifically vinegary. So it makes sense to look at the causes of sour breath and a sour taste, which are well described.

A sour taste often comes with it. If that is your main symptom, see our page on sour taste in the mouth.

• Acid reflux. The NHS lists an unpleasant sour taste caused by stomach acid as one of the two main symptoms of reflux, with bad breath, hoarseness, a recurring cough and bloating as other possible signs. Symptoms are often worse after eating, lying down or bending over.
• Acidic or fermented food and drink. Vinegar dressings, pickles, kombucha, wine and cider leave a smell for a few hours.
• Dry mouth. With less saliva, mouth bacteria multiply and the mouth is less able to neutralize acids. The NHS lists dehydration, medicines, nighttime mouth breathing and anxiety as common causes.
• Ketones. Fasting, very low-carb diets and diabetic ketoacidosis produce acetone, usually described as fruity or like nail polish remover rather than vinegar. Some people describe it as sharp or acidic, so if you have diabetes and feel unwell, check your ketones.

The NHS suggests eating smaller, more frequent meals, avoiding food within 3 or 4 hours of bed, raising the head of the bed by about 10 to 20 cm so your chest is above your waist, avoiding tight waistbands, stopping smoking, limiting alcohol and identifying trigger foods. A pharmacist can advise on antacids for short-term relief.

Cleveland Clinic's advice for a sour or bitter taste adds chewing sugar-free gum to increase saliva and rinsing with water. Cleaning your teeth and tongue removes the bacterial part of the smell, though it will not stop reflux itself.

Cleveland Clinic lists smoking, poor oral hygiene, infections such as colds, sinusitis and oral thrush, and medicines including some antibiotics, antihistamines, antipsychotics and chemotherapy among the causes of a sour taste, and anything that changes taste tends to change how your breath seems to smell as well. Smoking also dries the mouth and raises the risk of gum disease. If a sour smell started soon after a new medicine, ask the prescriber whether it is a known side effect rather than stopping it yourself. A sour taste that comes with weight loss, tiredness or feeling generally unwell deserves a check-up, because Cleveland Clinic notes it can occasionally be linked to diabetes, liver disease or kidney disease.

The NHS advises seeing a GP if heartburn happens most days, if lifestyle changes and pharmacy medicines do not help, or if you also have food sticking in your throat, frequent vomiting or weight loss without trying. Cleveland Clinic considers reflux at least twice a week over several weeks a reason for assessment, since it may be gastroesophageal reflux disease (GERD) and treatment can prevent damage to the esophagus.