Yes, it's allowed. We're supposed to take them out and show them but that was nice of them to ask you. Next time, just pull it out and say it's for the baby.

Foreign airports may not be so flexible so be aware.

There are also issues with the age of the child but don't worry about that until they walk. All of a sudden, it seemed, my kids were too old for the water.

Oh well. Being out 79 cents is less the issue than having enough time to buy more (overpriced) after security so keep this in mind.