Papaya whitening: Is it safe and effective?

Visit a supermarket and you are sure to find a TON of whitening products. Among the most common here in the Philippines is the use of papaya soap. Papaya is claimed to help whiten the skin and is a common ingredient in lotions and soaps, which can be cheaply bought off supermarket shelves.

According to papaya whitening advocates, papaya contains papain which is the effective "whitening" ingredients. So what is papain and how does it "whiten" the skin?



(Note: Most people here in the Philippines are obsessed with white-ness which is associated with people's socio-economic status. White = rich. Yes, that applies to all Americans and Europeans and other light skinned peoples regardless of socio-economic status. Filipino logic. /rant)  

According to the US FDA, papain is a "a protein-cleaving enzyme derived from papaya fruit (Carica papaya) and certain other plants." Cleaving? So it destroys protein? Apparently, yes. Papain is commonly used as a meat tenderizer for tough meat fibers. Also according to this Wikipedia article, it is used as a home remedy for bee stings and such as it is believed to break down the toxins which are made of protein.

Meat cleaver facial? No thanks. (from whatsontianjin.com)

So how does it whiten the skin? To be honest, I cannot find any published study on the mechanism of whitening with the use of papain. However, I did find some forum posts and this article from wisegeek.com which say that papain acts as an exfoliant. In short, papain only serves to remove the old skin cells and expose the lighter cells but it does not inhibit the production of melanin which gives us our basic skin tone. 

How safe is it as an exfoliant then? Again, I could not find any study indicating the safety of papain when used in skin care products. What I found instread is an FAQ by the US FDA on ordering the cease production of topical drug products with papain. These papain-containing ointments used to remove dead tissue in wounds are not approved by the US FDA and consumers are warned against the effects allergy due to papain. But removal of dead tissue sounds a bit like exfoliation for me. I'd test patch first should I plan to use papaya products (unlikely). I also came across this article (link) advising pregnant women to avoid papaya (which is used in some countries as a herbal medicine for abortion), although I cannot find supporting evidences for the said warning. 

Summary:
Efficacy: possible, as an exfoliant. 
Safety: may cause severe allergic reactions, possibly unsafe. I'd do a test patch first and I better be sure I'm not pregnant (safety first).