Fun with Vibrators, Ice, and Pain by Amy Baxter

Scientists have postulated since 1965 that vibration or cold can gate out sharp pain. Humans have known this since the first time someone rubbed a bumped elbow or shook a hand after hitting a thumb with a hammer. For the first time, a device taking advantage of the body's natural defenses against pain has been created, and is helping kids and needle-fearing folk worldwide.