Since your body gets dehydrated overnight, it's not uncommon to wake up thirsty. But whether or not you should sip from the glass you left on the nightstand (was it last night? The night before?) is up for debate.
What can get in the open glass?
You probably know that drinking water left in an open glass is not super sanitary. Dust, debris, and even the odd passing mosquito can drop into the glass overnight, leaving an unhealthy surface scum. Even a closed container like a bottle or pitcher introduces problems, mainly because our skin is coated with sweat, dust, skin cells, and even nasal discharge, so once we put the bottle in our mouth, these can all "backwash" into the remaining water, causing contamination. Our saliva also carries bacteria, which does the same. "If it's allowed to incubate for hours, that could potentially contaminate the water, and make you ill by reintroducing that bacteria," says Marc Leavey, MD, primary care specialist at Mercy Medical Center in Massachusetts. "Once you have put your lips to the bottle, you should consume that bottle in one sitting and then discard it."
Could you get sick from drinking a glass of water that has been sitting overnight? ...