How does ice help a sprained ankle?

Ice: In the first 6 to 12 hours of a an injury ice can act as an anti-inflammatory.

To ice or not.: After tissue damage, the body engages defensive mechanism known as the inflammatory response. To control blood loss, initially, there is severe constrictions of the blood vessels injured in the area. This is where ice helps with the injury. It aids the body in minimizing fluid loss to keep swelling to a minimum. The problem is, if too much cold is applied too long, the healing can be slowed.