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Could Your Water Bottle Make You Sick?

May 08, 2024May 08, 2024

Here's how to keep it sparkling clean—yes, even the lid.

Washing your reusable water bottle can be an easy chore to overlook—until you pop off the lid to give it a refill and notice a ring of scum. Those smaller bits—like the lid and/or straw—make water bottles tricky to clean (almost on the same level as cleaning a Keurig, although nowhere near as tricky as a complicated appliance like a dishwasher). It begs the question: Can your S'well, Stanley, Owala, or other preferred water bottle make you sick if you forget to wash it? And how do reusable water bottles get dirty if they're just filled with H20?

To answer that last question: Hi, it's you. You're the problem, it's you. More specifically, your mouth bacteria. Those slimy rings that you may notice on the lip or spout of your water bottle are biofilms, and they're there because bacteria from your mouth produces "a sticky residue called exopolysaccharide," says microbiologist Jason Tetro, author of The Germ Code and The Germ Files and host of the Super Awesome Science Show podcast. He explains that this residue "allows bacteria to stick and grow in that spot."

But biofilms aren't inevitable facts of life you have to accept; just regularly clean your bottle. If you're using your bottle daily (high five for hitting those hydration goals and reducing single-use plastics!) you should rinse it out and fill it with super hot water every day, says Tetro.

Then, at least once a week, use dish soap to get your bottle clean and employ a bottle brush to wash the straw and sipping components of your bottle, he recommends. This will help prevent the formation of those biofilms.

Of course, any time you notice a funky smell or off taste from your bottle, it's a sign you should give it a good wash, Tetro says. As far as germs in your water bottles go, they're probably not going to make you sick. "If you're using your water bottle, then, for the most part, they are your germs," he explains. "There's very little likelihood you can get sick from them."

But if you share your water bottle with friends or family, and they're showing signs of a respiratory illness like a cough, runny nose or sneezing fits, that's a different scenario.

"The most likely route of infection transfer is bodily fluids and saliva is a very good one," Tetro says. (Researchers, for example, say shared water bottles could have been at play in a Strep outbreak that affected 14 college students on a judo team a decade ago).

When it comes to washing your water bottle like a pro, cleaning expert Muffetta Kruger, the founder of Muffetta's Domestic Assistants, recommends avoiding any harsh chemicals or abrasive scrubs because they could damage the bottle, and any cracks could become mold hideouts. Check your water bottle's instructions to see if it's dishwasher-safe. If it is, place it on the top rack of the dishwasher, Kruger suggests, but still remove the more intricate parts to hand wash.

When hand-washing, follow these three steps, says Kruger:

Wash with hot, soapy water. Start by rinsing the bottle with hot water, then wash it thoroughly with a mild dish soap. Pay extra attention to the mouthpiece, cap, and any hard-to-reach areas. Use a bottle brush to scrub the inside and the straw.

Rinse and sanitize. After washing, rinse the bottle thoroughly to remove any soap residue. You can then go the extra mile and sanitize the bottle by soaking it in a solution of water and white vinegar (1 part vinegar to 3 parts water) for about 5 minutes. Rinse again with hot water.

Air-dry the bottle completely. Dampness can trigger the growth of bacteria and mold, so allow the water bottle to air-dry completely before screwing on the cap or storing it.

Complete the three-step process once a week for a deep clean, and you can hydrate happily and safely.

Brittany Anas is a former newspaper reporter (The Denver Post, Boulder Daily Camera) turned freelance writer. Before she struck out on her own, she covered just about every beat—from higher education to crime. Now she writes about food, cocktails, travel, and lifestyle topics for Men’s Journal, House Beautiful, Forbes, Simplemost, Shondaland, Livability, Hearst newspapers, TripSavvy and more. In her free time, she coaches basketball, crashes pools, and loves hanging out with her rude-but-adorable Boston Terrier that never got the memo the breed is nicknamed "America’s gentleman."

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Wash with hot, soapy water. Rinse and sanitize.Air-dry the bottle completely.