How dirty can water be?

Experts say reusable bottles get grubby no matter what liquid they're filled with, and it's important to clean regularly.

Water bottles pick up germs from our mouths when we take a sip, and from our hands when we touch the straw or lid. They're covered in tough-to-reach nooks and crannies which can become a breeding ground for bacteria if left un-scrubbed.

Unclean water bottles can cause stomach aches and itchy throats and also exacerbate allergies and asthma. Sharing with a friend can get them sick too — especially during cold and flu season.

Experts disagree on how often you should wash and how, but they're all in agreement on one thing: give your water bottle a tender loving clean, because something is better than nothing at all.

"Any water bottle, plastic or metal or reusable. If you're gonna use it again, I think of it like a dish, right? Like you're not gonna use a fork again and again and again without washing it or a spoon," said Dr. Mike Ren, a family medicine physician at Baylor College of Medicine.

Washing with soap and water, in the dishwasher and using denture tablets are all good ways to clean a water bottle.

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