Yes, your water bottle should be washed: doctors have explained why and how often

According to experts, germs accumulate on the walls and cap over time, and therefore the bottle should be cleaned regularly, Medicalxpress reports.

As experts explain, bacteria get inside from the surface of the hands and through the mouth with every sip. The inner walls, cap and tubes have tiny hard-to-reach crevices where mould and bacterial plaque can easily form, especially if the bottle is not cleaned for a long time.

"It seems like a small thing, but it's actually extremely important," notes University of Pittsburgh nurse Michelle Knepper. She says a dirty bottle can cause stomach aches, a sore throat, and even aggravate allergies or asthma.

Medical professionals argue about the frequency of cleaning, but all agree on one thing: It' s better to wash at least a little than not at all.

"It's not a huge problem, but it's also not hard to just rinse the bottle with soap and water," adds family physician Mike Wren of Baylor College of Medicine.

How to properly wash a bottle

The type of material doesn't matter - plastic, glass or metal become home to germs over time. And plastic containers are especially vulnerable, with micro-cracks inside them where bacteria can easily breed.

The easiest way to clean them is with warm water and soap and a brush. Wash inside and out, then rinse thoroughly and allow the bottle to dry. For tubes or narrow necks, a bottle brush or fine cleaner will do.

For deeper cleaning, you can put the bottle in the dishwasher if it's safe for the material, or fill it overnight with dissolved denture cleaning tablets. Vinegar or baking soda diluted in warm water will also work.

Most experts advise washing the bottle with soap and water every day, and once a week a more thorough cleaning. If time is short, it is enough to do it at least once every few days, not forgetting to rinse the cap and neck with each filling.

Daily washing is especially important if you fill the bottle not only with water, but also with sweet or protein drinks: residual sugar creates a breeding ground for bacteria.

Is it okay to leave water out overnight?

The opinions of experts are divided. Some advise pouring out leftover water after each use, others advise every few hours. According to Dr Wren, you can leave some water overnight, but the old liquid should be poured out every couple of days.

If you can see plaque on the walls or get an unpleasant odour, you should not drink from the bottle. Disposable plastic bottles should also not be reused - they crack more easily and release chemicals.

University of Georgia hospitality researcher Ivy Sun, who studies reusable bottle contamination, washes her own and her children's containers every day.

"It's a small habit that can have a serious impact on our health," she emphasises.