Two moms from Canada, Marie-Pier L’Hostie and Penny Powell, shared some viral Facebook posts last week. It was about mold that might build up in an anti-spill sippy cup for children. The major problem: the mold is only noticeable if you crack open the cup's anti-spill guard top.

This is the post:

It reads:

My friend Simon O’kanada wondered why his son was always sick. He broke the anti-spill top of his “Tommee Tippee” bottle and discovered mold inside the mouthpiece.

It doesn’t wash and can’t be seen unless it is broken open. He called the company, and the lady on the phone laughed out out loud. Several moms on other groups have also discovered mold after my post in another Facebook group, so I’m sharing you. If you please, those who have these cups, pay attention! Being washed by hand or in the dishwasher, the mold will stay there.

The story first came from a Facebook group for mothers. They shared the story from a dad named Simon O'kanada who wondered why his child kept getting sick.

It reads:

My friend wondered why his son was still sick so he broke open the anti-spill guard of his Tommee Tippee glass and discovered mold inside the anti-spill top that does not wash that you can’t see except if you break it open. He called the company and the lady on the other end laughed in his face.

Several moms on the other group also found mold after my post about it in another group so I’m sharing with you. Those of you with these cups pay special attention, he has washed it with his hands and in the dishwasher, etc., and the mildew has stayed anyway! Share it!

After having received several messages from parents who have opened their children’s anti-spill cup, it is important to do something, so for parents who discover that they have the same problem with the anti-spill top, please, I invite you to complain to consumer protection and also the customer service of the company described — thank you! Share in large numbers.

It's definitely one of the most shocking things you'll ever read. But that's not the worst part yet. You can't tell if there's mold.

Until you crack open the mouthpiece.

It's FULL OF IT.

The sippy cup was made by Tommee Tippee, a very popular brand among parents.

If you don't crack open the top, you won't be able to get rid of the mold, even if you wash it by hand.

Obviously, parents are horrified, and so is Tommee Tippee, we're guessing. They decided to respond on social media:

Does this happen to all sippy cups? Will Tommee Tippee be able to survive this?