Horrified parents are prising open their kid's sippy cups with disgusting results.

It’s been the story that many of us simply don’t want to read because well, it’s simply disgusting.

But it’s been hard to ignore hasn’t it? All those graphic images of revolting surprises lurking inside our kid’s drink bottles and sippy cups coming up in our news feeds.

After all, who breaks open the seals of their children’s sippy cups to actually look for mould?

Well, I for one will be doing it now!

It first cropped up a few weeks ago when a British man posted a rather stomach churning image of his daughter’s daughter’s ‘Sistema’ drink bottle.

Craig Beresford from the UK said that despite “cleaning the bottle and cap every day,” he couldn’t work out what was giving his seven-year-old daughter an upset stomach.

“I figured it might be the Sistema bottle. It’s the only constant item she has had contact with the whole time.”

Craig said he was “OCD about keeping things clean,” prized open the bottle’s cap with a knife.

The cap, which Craig insists was rinsed and sterilised every day, isn’t designed to break in two and took a fair amount of force to dissemble.

And when he did, well, look for yourself.

“The internal components had been hoarding bacteria,” Craig explained. “We were horrified and heartbroken that our little girl had been using the bottle in this state.”

The grime had, according to Craig, accumulated in between the two parts of the cap, which twist together to form the suction part of the bottle.

Then this week a father in Montreal, also wondering why his son was sick and decided to open the "leak-proof" top of his sippy cup.

The results? Well pretty similar.

Marie-Pier S. L'Hostie shared a photo of her friend’s child’s mouldy cup on Facebook with a warning to other parents.

“It doesn’t wash and can’t be seen unless it is broken open,” she explained in the post.

“He called the company, and the lady on the phone laughed out loud. Several mums on other groups have also discovered mould …

“Those who have these cups, please pay attention! Being washed by hand or in the dishwasher, the mould will stay there!”

The discovery has prompted parents right around the world getting out their tools and prising open their kid’s sippy cups and bottles – many with similar horrifying results.

“This is so crazy, we just had the same problem (but we caught it sooner)! When my son refused his Tommee Tippee cup I decided to try it. And I immediately had to run to the sink and and spit out the milk!! Old milk (more like cheese) was trapped in the mouth piece. I could tell it was going to be near impossible to clean (poor design). So I threw it out. Glad it didn't get to THIS point. Great company. Love their baby bottles. But bad product” wrote one mum.

“I noticed this with Aaron's sippy cups a while ago! I couldn't believe that these valves were not washable on the inside. I threw the valves out after the second wash noticing that the inside couldn't be cleaned. Totally a waste of money.” Wrote another.

The dangers of mould inside these children's products are wide ranging, from triggering asthma attacks to being linked to skin and respiratory infections, yeast infections, headaches, aching joints, asthma, fatigue, depression and anxiety.

Sistema, the manufacturer of the original bottle that was posted about responded to customer’s complaints.

General Manager, John Prest, said on their website “A number of our customers have recently advised us that they are having difficulty cleaning our Twist 'n' Sip drink bottle caps.

“We take this feedback very seriously and have posted on the home page of our website an announcement regarding this issue.

“We manufacture our caps to meet international child safety standards and it is for this reason they can be difficult to disassemble.

“Sistema is committed to producing products that fulfil all our customer’s needs and our team is currently working on a number of design improvements to ensure our caps meet this criteria. Our Customer Service teams are happy to help anyone who has any further enquiries.”

Tommee Tippee, the second manufacturer whose sippy cups worried the father in Montreal, told Buzzfeed News in a statement it “always welcome parents’ feedback, comments and ideas”.

“We continually develop our products and look for ways to improve them, so feedback from parents is vital to us. Positive feedback tells us we’re doing the right thing, but just as importantly, like all companies, we learn even more when negative experiences are brought to our attention,” it said.

“We’ve sold millions of Sippee cups and have had some very positive feedback. However, we know from visitor posts that a few people have not had a good experience with the valve part of the cup. For this we sincerely apologise and we are actively following up on any concerns raised.”

Have you had similar concerns about your child's sippy cups?