Papaya contains a natural enzyme called Papain. Papain is known to be a good a good natural pain reliever and is a matter of fact, now being sold in supplement forms in the market. Papain is also known to be effective in treating sore throat and shingles and other inflammation. However, more research needs to be done to prove its efficacy as a pain killer.
Read more information here: http://altmedicine.about.com/b/2013/06/12/easing-pain-with-papain.htm