You Asked
How does aspirin work? — Annie, Orchard Park, N.Y.

Marshall Answered
The basic idea behind aspirin is to block a chemical message that normally signals pain inside your body.

Normally, a damaged cell in your body will release chemicals called prostaglandins. Prostaglandins are made by COX-2 enzymes. The prostaglandins cause the pain nerves near the damaged cells to register pain and send the signal to your brain.

Aspirin blocks the action of COX-2. So less prostaglandins are made, and pain signals are diminished.

Like all drugs, aspirin has side effects. For example, aspirin also happens to block the action of COX-1, which helps maintain the lining of your stomach. This is why aspirin causes stomach problems for some people.

See how aspirin works for details.