Editing Sunscreen (section)

==== Persistent pigment darkening ====
The persistent pigment darkening (PPD) method is a method of measuring UVA protection, similar to the SPF method of measuring sunburn protection. Originally developed in Japan, it is the preferred method used by manufacturers such as [[L'Oréal]].

Instead of measuring [[erythema]], the PPD method uses UVA radiation to cause a persistent darkening or tanning of the skin. Theoretically, a sunscreen with a PPD rating of 10 should allow a person 10 times as much UVA exposure as would be without protection. The PPD method is an ''[[in vivo]]'' test like SPF. In addition, the European Cosmetic and Perfumery Association (''Colipa'') has introduced a method that, it is claimed, can measure this ''[[in vitro]]'' and provide parity with the PPD method.<ref>{{cite web|url=http://www.colipa.com/site/index.cfm?SID=15588&OBJ=28546&back=1 |title=Method for the in vitro determination of uva protection provided by sunscreen products, 2007a |website=www.colipa.com |date=June 9, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080609221030/http://www.colipa.com/site/index.cfm?SID=15588&OBJ=28546&back=1 |archive-date=June 9, 2008 }}</ref>