Ask the doctor: How does hot pepper cream work to relieve pain?

Q. I have pain from osteoarthritis in both knees. I'm curious about the cream made from a substance in hot peppers. How does it relieve pain?

A. You're referring to capsaicin, the substance in chili peppers that gives them their hot taste. Capsaicin is an ingredient in many over-the-counter topical pain-relief preparations, which include creams, gels, lotions, patches, and sticks. When first applied, topical capsaicin causes a burning sensation. This sensation lessens within a few minutes, and also over time with repeated applications. There are few, if any, systemic side effects.