NEW YORK (CBSNewYork)– Get ready to cringe. Parents may want to check their kid’s sippy cups after finding out what some people have found in the lids.

A popular brand of sippy cups has a nasty surprise lurking, but you wouldn’t know it unless you slice open the mouthpiece.

“Just disgust, I mean I probably wouldn’t have bought them, clearly, if I knew they had this problem,” one father told CBS2’s Alice Gainer.

The problem: mold. And in some cases, not just a little bit.

“And I was like, oh my gosh I can’t believe it’s just been sitting in there and we were shocked that it would even be that much,” Sarah Wright, a concerned mother, told CBS2.

Parents from all over have been taking to social media to post pictures of their moldy sippy cup valves.

The company that makes them, “Tommee Tippee,” is now taking action, saying it’s launching a new sippy cup in the next few months. The new cup will have a two piece valve that can be used with different types of liquid, and is easier to clean.

In the meantime, they’re making transparent valves immediately available to parents. But some parents are already concerned about their children’s health.

“My kids have been kinda having colds lately, well maybe that’s why or are they going to get sick from this? Because we’ve only had them for four months,” Wright said.

“My first thought is the mold is disgusting to look at,” Dr. Laura Popper, a pediatrician, told CBS2.

Popper said parents shouldn’t be too worried.

“We eat cheese and all kinds of things that are, in fact, made of mold,” she said. “The mold in homes that is usually a problem is that which is inhaled. We have mold all over the place, but drinking this will probably have little effect.”

The mold grew despite parents washing the cups. Tommee Tippee has a video on their website explaining how to properly clean the valve, noting it should be hand-washed only. The company also advises using only milk, water, and juices without pulp.