You know your child is sick when...

You have stopped at the convenience store after school for the purpose of buying him a treat. You are standing with him in the candy aisle, asking him what he wants, and he says,

"I want to get a treat mom, but my tummy hurts."
"Do you want to pick one out now and we'll save it for later, when your tummy feels better?" you say,
"No, lets just wait." he says.

And so you walk out of the candy aisle and the store, empty handed.