A dad has warned parents over a 'hidden danger' lurking inside kids' water bottles after he made a disturbing discovery.

In a recentTikTokvideo, father Jason Sullivon told how he regularly rotates the reusable bottles his daughter uses each day, but found that he wasn't able to get them fully clean due to their lack of removable parts.

He says he then spoke to the manufacturer, Yeti, about the issue, who advised him to boil the bottles in hot water for five to ten minutes.

• Nationwide payments warning issued to millions of members


• Girl, 13, tragically dies after taking part in dangerous social media trend

After doing this, he was startled to discover a build-up of blackmould around the rubber seal.

He warned: "I contacted Yeti to ask how to clean them properly, since they are not designed to be taken apart. After doing that, this is what they looked like when they came out.

"If you’re using these types of bottles, especially for children, make sure to check them regularly. There could be hidden buildup or contamination you might not notice."

The video has since attracted over 130,000 likes on TikTok, with many users taking to the comments to share their own stories of tackling mould in their water bottles.

One aggrieved bottle owner penned: "So many drinking bottles are like this. It’s hard to find one that isn’t." While a different user commented: "It drives me crazy that all water bottles have so many extra parts to them making it impossible to properly clean."

But others said this was not an issue for them, as one mum wrote: "Pulled apart my sons 4yr old yeti [bottle]. Can confirm the amount of mould in this is so minimal, especially after 4 years of use. This is washed in a dishwasher 2-3 times per week and straws cleaned daily." Another comment read: "Thank you! Just checked ours and they were disgusting."

According to UK consumer watchdog Which?, parents can help prevent mould build up in children's water bottles by positioning them carefully in the dishwasher. If they have many difficult-to-reach parts, you can try washing them in the sink using very hot water and washing-up gloves, disassembling as many parts as possible for a deep clean.

Other options include using a bottle cleaning kit with pipe cleaners or a sterilising solution. You should always check the washing instructions issued by the manufacturer for your make of bottle.