Capsaicin is a substance found in hot chili peppers. When applied to the skin over the affected area, medicines containing capsaicin may be used as pain relievers for rheumatoid arthritis, post-herpetic neuralgia, and other conditions.

When applied to the skin, capsaicin affects the skin's nerve impulses, blocking the pain without blocking other sensations. Its use should be directed by a doctor. It may take several weeks to feel the effects of capsaicin.

Some people cannot tolerate capsaicin, which may cause burning, stinging, or redness of the skin. Capsaicin can cause extreme pain if applied to an open rash or if it gets in the eyes.