Can dehydration cause bad breath?

Dehydration means your body is losing more fluid than it takes in. One of the first places you notice it is your mouth: MedlinePlus lists a dry or sticky mouth among the signs of mild to moderate dehydration, and Cleveland Clinic lists dehydration as a cause of dry mouth.

Saliva is what normally keeps odor in check by rinsing your tongue and teeth. With less of it, bacteria on the back of the tongue have an easier time, and the sulfur gases they produce linger. Dehydration breath is essentially short-term dry mouth: it comes on with fluid loss and usually clears once you drink enough.

• Exercise and heat. Sweating heavily without replacing fluids, especially if you also breathe through your mouth while training.
• Illness. Fever, vomiting and diarrhea all drain fluids. The NHS lists these among dehydration causes.
• Alcohol. NIAAA explains that alcohol suppresses vasopressin, a hormone that tells the kidneys to hold on to water, so you urinate more. See alcohol and bad breath.
• Not drinking enough during a busy day, or long flights in dry cabin air.
• Diuretic medicines that make you urinate more.
• Fasting, when you also go without fluids for many hours. See fasting and bad breath.

Babies, young children and older adults are more at risk of dehydration, according to the NHS.

If your mouth stays dry even when you drink plenty, read dry mouth and bad breath instead.

1. Drink enough that your pee is pale. That is the NHS's simple guide. Water is the best choice; diluted sugar-free squash also counts.
2. Drink more when you are losing more, such as when exercising, in hot weather or when you have a fever, vomiting or diarrhea.
3. Sip steadily rather than drinking a lot at once, especially if you feel sick.
4. Clean your tongue once you are rehydrated. Coating that built up while your mouth was dry will not rinse away on its own.
5. Chew sugar-free gum to get saliva flowing again.
6. Go easy on alcohol and caffeine, which NIDCR notes can dry the mouth.

Mints and mouthwash can make your mouth feel fresher, but alcohol-based rinses may dry it further.

Mild dehydration is easy to fix at home. The NHS advises getting medical help if you are still peeing little or very dark urine despite drinking, feel dizzy when you stand that does not go away, are unusually tired or confused, or cannot keep fluids down. MedlinePlus lists signs of severe dehydration including no urination, very dark urine, rapid heartbeat, rapid breathing, sunken eyes, and irritability or confusion. Babies and older adults need help sooner.