How to Keep Your Water Bottle Clean and Safe

Reusable water bottles are an eco-friendly way to stay hydrated, but using your water bottle over and over again without ever washing it isn’t an ideal choice for your health.

“If you don’t clean your water bottle, mold and bacteria will start to grow,” says Amy Edwards, MD, a pediatric infectious disease specialist and Associate Medical Director of Pediatric Infection Control at University Hospitals Rainbow Babies & Children’s. How risky that may be for your health depends on several factors.

How Dirty Water Bottles Can Affect Health

Dr. Edwards says that not washing your water bottle for a day or so after using it probably isn’t going to be a big deal, if you:

• Are generally in good health and your immunity isn’t compromised.
• Don’t share your bottle with anyone else.
• Only put water in the bottle (and ice, but nothing else).
• Empty it and let it dry completely between uses.

“Most immune systems can handle skipping a day or two,” says Dr. Edwards. “The biggest risk is that the bottle will start to smell bad.” Eventually, bacteria from your mouth will cause mold to grow in the bottle. This can not only make the bottle develop a bad taste, it can also produce spores that trigger asthma or allergy symptoms, she says.

If you don’t wash it for a long time, worse things can happen. “If it gets really nasty, your own bacteria can make you sick,” she says. You might experience nausea or an upset stomach.

Habits That Increase Health Risks

There are other factors that can increase or speed up contamination of your water bottle and make it a bigger risk to your health. These include:

• Putting juice or other sweetened beverages in your water bottle. “This can speed up the production of bacteria and mold because they have the sugar to feed on,” says Dr. Edwards.
• Using your water bottle for coffee or tea with milk or sugar. “Similarly, these drinks contain fat, protein and sugars that bacteria and mold can grow off of,” she says.
• Sharing your water bottle. “Bacteria from other people is more likely to make you sick.”
• Touching your water bottle. If you touch your water bottle without washing your hands first, you can transfer bacteria to your water bottle, including E. coli, which can cause diarrhea and other stomach problems.
• Exposing your bottle to environmental bacteria. Two types of bacteria, Serratia marcascens and Pseudomonas aeruginosa, can be transferred to your bottle when you touch contaminated surfaces or if they’re present on dust, dirt or water that gets in your bottle.

If you have an autoimmune condition or are receiving any kind of treatment that can reduce your immunity (like cancer treatment), it’s important to wash and keep your water bottle as clean as possible and let it fully dry between uses. “If your immunity is compromised, mold and bacteria can become a problem quicker,” says Dr. Edwards.

Does Material Make a Difference?

Research suggests that plastic water bottles (made from polyethylene terephthalate) collect much higher amounts of bacteria and mold than stainless steel ones.

“There are certain surfaces that are easier for bacteria and mold to stick to – and harder to get them out of,” says Dr. Edwards. “But washing your water bottle regularly is more important than the material it’s made of.”

She recommends going with a simple stainless steel bottle, ideally one with a screw-on lid and an opening that closes with a seal, so the lid is the main thing that gets dirty. “The simpler the bottle, the easier it is to clean and the more likely you are to wash it regularly,” she says.

Dr. Edwards suggests avoiding:

• Reusable straws and nozzles, which require a bottle brush to clean.
• Bottles that have multiple crevices or parts that you need to take apart to clean.

7 Tips to Keep Your Water Bottle Clean and Safe

Choosing a reusable water bottle over single-use bottles is still a much better choice, even if keeping it clean takes a little effort, says Dr. Edwards. Here are seven easy ways to care for your reusable water bottle – and prevent it from becoming a breeding ground for mold and bacteria.

1. Try to wash your water bottle between uses, or at least after every other use at the minimum, says Dr. Edwards. (If your immunity is compromised, it’s essential to wash your water bottle after every use.)
2. Don’t just rinse it. While rinsing may help a little, it’s not going to clear mold or bacteria from your bottle. “If it's a dishwasher-safe water bottle, pop it in the dishwasher,” she says. “Otherwise, a clean bottle brush, warm soapy water and a good scrub should be sufficient.” Using bleach or heavier duty cleaners is unnecessary.
3. Let it dry completely between uses. “Bacteria in the mouth prefer moist environments, so letting your water bottle dry all the way can kill most oral bacteria,” says Dr. Edwards.
4. Only use fresh water in your water bottle. If you’re adding electrolyte packets or putting energy drinks or other beverages that contain sugar, dairy or proteins in your water bottle, you really should wash it afterward, she says.
5. Avoid sharing your water bottle with others. Everyone carries bacteria in their mouths, and sharing water bottles means sharing bacteria and other germs that can contaminate your water bottle and be more harmful to you. (Yours can be more harmful to others too.)
6. Keep your bottle top closed. Only open your bottle to sip from it, and then close it again to reduce the risk of environmental bacteria getting inside it, especially if you’re taking it to work, to the gym or out in public. “You don't want the bottle just sitting around open, letting everything fall into it,” says Dr. Edwards. “That absolutely can make you sick.”
7. Take care of your teeth and gums. Brushing your teeth, flossing, using mouthwash and practicing good oral hygiene helps keep your mouth clean, supports overall health and it helps prevent “bad” oral bacteria from getting into your water bottle. “Just think, if you're struggling with a gum infection like gingivitis, that bacteria is going to get in your water bottle,” she says. If you don’t wash the bottle, more bacteria is going to go back into your mouth too, which may worsen your gum health.

“I don't want people to worry so much about germs that they think they have to switch to disposable water bottles,” says Dr. Edwards. “Not washing your bottle after every use isn’t going to kill you, but you should try to remember to do it as often as possible.”

Dr. Edwards admits that she doesn’t always get around to washing her water bottle every day. “I'm an infectious disease doctor, and even mine usually only gets washed three or four times a week,” she says. “But I'm not immune-compromised, I only put water in my bottle and I don’t share it with anyone else.”

Related Links

University Hospitals infectious disease specialists provide expert care for patients to help them stay healthy and safe.