Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the active ingredient found in chilli peppers and it is this that gives them their heat.
The Capsaicin has a wide range of benefits to offer, including analgesic properties that act as a form of pain relief that includes acetaminophen, which can be found in Paracetamol! Because of this, it has been used for hundreds of years to control muscle and joint pain as it inhibits the release and movement of Substance P, a chemical form of pain impulses that travel along the central nervous system. For example, when substance P enters joint tissue, it causes inflammation and contributes to rheumatoid arthritis.
Capsaicin can help to relieve the pain by preventing a buildup of substance P in pain receptors, so when it fails to build up in the nerve endings, the pain is not transmitted to the brain!