Capsaicin

Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is an alkene of biological importance and active component of chili peppers.  It's what makes chili peppers hot!   Capsaicin is most often used as a topical analgesic and exists in many formulations of cream, liquid, and patch preparations of various strengths; however, it may also be found in some dietary supplements.