Daniel had a headache. Mom gave him Advil. The headache went away.

So he asked the obvious question. How did the Advil know to go to his head?

It didn't.

When you swallow ibuprofen, it dissolves in your stomach, gets absorbed into your bloodstream, and your bloodstream carries it all around your body. Your feet get Advil. Your elbows get Advil. Your fingernails get Advil. Your body doesn't know where the medicine is needed. It just lets the bloodstream deliver it everywhere.

The headache went away because that is where the problem was.

Here is what was actually happening. When your body is injured or inflamed, it often releases chemicals called prostaglandins. They help create inflammation, make nerves more sensitive to pain, and can contribute to fever. They are your body's alarm system -- useful signals that someth ...