Why do you get bad breath after drinking alcohol?

• Dry mouth. Cleveland Clinic notes that alcohol can dry out your mouth, and NIDCR advises people with dry mouth to avoid alcohol for that reason. Less saliva means bacteria on the tongue thrive.
• Dehydration. NIAAA explains that alcohol suppresses vasopressin, a hormone that signals the kidneys to keep water, so you urinate more and lose fluid. That adds to the dry mouth the next morning.
• The drink itself. Beer, wine and spirits all leave their own aroma, and sugary mixers feed mouth bacteria.
• Snoring and mouth breathing. The NHS advises not drinking too much alcohol if you snore, and snoring often goes with sleeping with your mouth open, which dries it out.
• Late-night food and skipped brushing, which leave food and plaque in place for hours.

Some alcohol breath comes from the mouth, but some comes from alcohol circulating in your blood and passing into the air in your lungs, which is the basis of the breath-alcohol tests police use. Mints, gum and mouthwash can freshen the mouth for a while, but they cannot change what you are breathing out from your lungs. That part fades as your body clears the alcohol. If you need to know whether alcohol is still in your system, smell is not a reliable guide; time is.

Skip alcohol-based mouthwash the morning after. It can dry the mouth further. Our guide to mouthwash for bad breath explains alternatives.

MedlinePlus lists alcohol use disorder among the causes of breath odor. Heavy, long-term drinking keeps the mouth dry and often goes together with smoking, both of which make bad breath and gum problems more likely. If bad breath is a daily issue and you drink most days, cutting back is likely to help your breath as well as your health. The NHS bad breath advice simply says: do not drink too much alcohol.

Very heavy drinking over years can also damage the liver, and advanced liver disease can change breath odor; a breath study of liver patients linked this smell mainly to a sulfur compound called dimethyl sulfide. That is a medical problem, not a hygiene one.

If bad breath continues on days when you have not been drinking, look for other causes such as tongue coating, gum disease or tonsil stones. See a doctor if you notice yellowing skin or eyes, swelling in your belly, confusion, or a sweet, musty breath odor, which can point to liver problems, or if you are worried about how much you drink.