Is it safe?
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 bedside table (was it last night – or 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. 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 Dr Marc Leavey, a primary care specialist. “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?
But let’s get real: Since it’s your own bacteria, it’s unlikely that you’ll actually get sick. Though no one brags about it, many people sip from used drinking glasses, mugs and bottles without any ill effects. But it’s certainly not advisable to share your bottle with someone else. Neither should someone with a reduced immune system, such as transplant patients, those undergoing chemotherapy, or people living with HIV/AIDS, be exposed to contaminated water.
And it makes no difference whether it’s bottled or tap water. It’s a common myth that bottled water is cleaner than tap. Both have to meet exacting hygiene standards.