Editing Sunscreen (section)

=== UVA protection ===

==== 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>

==== SPF equivalence ====
[[File:UVA logo.svg|thumb | upright=0.5 | The UVA seal used in the [[European Union|EU]] ]]
[[File:SPF15SunBlock.JPG|thumb|upright| A tube of SPF 15 sun lotion]]
As part of revised guidelines for sunscreens in the EU, there is a requirement to provide the consumer with a minimum level of UVA protection in relation to the SPF. This should be a UVA protection factor of at least 1/3 of the SPF to carry the UVA seal.<ref>{{cite web|url=https://www.cosmeticseurope.eu/using-cosmetics-colipa-the-european-cosmetic-cosmetics-association/sun-products/the-european-commission-recommendation-on-the-efficacy-of-sunscreen-products.html|title=www.cosmeticseurope.eu|url-status=dead|archive-url=https://web.archive.org/web/20140826114843/https://www.cosmeticseurope.eu/using-cosmetics-colipa-the-european-cosmetic-cosmetics-association/sun-products/the-european-commission-recommendation-on-the-efficacy-of-sunscreen-products.html|archive-date=August 26, 2014|df=mdy-all}}</ref> The 1/3 threshold derives from the European Commission recommendation 2006/647/EC.<ref>{{Cite web |last=Cosmetics Europe |date=February 2009 |title=N° 23 IMPORTANT USAGE AND LABELLING INSTRUCTIONS FOR SUN PROTECTION PRODUCTS |url=https://www.cosmeticseurope.eu/files/9814/6408/4022/CR-23-Sunscreens_Labelling.pdf |archive-url=https://web.archive.org/web/20220305123301/https://www.cosmeticseurope.eu/files/9814/6408/4022/CR-23-Sunscreens_Labelling.pdf |archive-date=2022-03-05 |access-date=2022-06-27}}</ref> This Commission recommendation specifies that the UVA protection factor should be measured using the PPD method as modified by the French health agency [[Agence nationale de sécurité du médicament et des produits de santé|AFSSAPS (now ANSM)]] "or an equivalent degree of protection obtained with any in vitro method".<ref>{{Cite web |date=2006-09-26 |title=Commission Recommendation of 22 September 2006 on the efficacy of sunscreen products and the claims made relating thereto (notified under document number C(2006) 4089) (Text with EEA relevance) |url=http://data.europa.eu/eli/reco/2006/647/oj/eng |language=en}}</ref>

A set of final US FDA rules effective from summer 2012 defines the phrase "broad spectrum" as providing UVA protection proportional to the UVB protection, using a standardized testing method.<ref name="fda2011" />

==== Star rating system ====
In the UK and Ireland, the [[Boots (chemist)|Boots]] star rating system is a proprietary ''[[in vitro]]'' method used to describe the ratio of UVA to UVB protection offered by sunscreen creams and sprays. Based on original work by Brian Diffey at [[Newcastle University]], the Boots Company in Nottingham, UK, developed a method that has been widely adopted by companies marketing these products in the UK.

One-star products provide the lowest ratio of UVA protection, five-star products the highest. The method was revised in light of the Colipa UVA PF test and the revised EU recommendations regarding UVA PF. The method still uses a [[spectrophotometer]] to measure absorption of UVA versus UVB; the difference stems from a requirement to pre-irradiate samples (where this was not previously required) to give a better indication of UVA protection and photostability when the product is used. With the current methodology, the lowest rating is three stars, the highest being five stars.

In August 2007, the FDA put out for consultation the proposal that a version of this protocol be used to inform users of American product of the protection that it gives against UVA;<ref name="qa2007"/> but this was not adopted, for fear it would be too confusing.<ref name="onpoint" />

==== PA system ====
Asian brands, particularly Japanese ones, tend to use The Protection Grade of UVA (PA) system to measure the UVA protection that a sunscreen provides. The PA system is based on the PPD reaction and is now widely adopted on the labels of sunscreens. According to the Japan Cosmetic Industry Association, PA+ corresponds to a UVA protection factor between two and four, PA++ between four and eight, and PA+++ more than eight. This system was revised in 2013 to include PA++++ which corresponds to a PPD rating of sixteen or above.

==== Expiration date ====
Some sunscreens include an [[expiration date]]—a date indicating when they may become less effective.<ref>{{cite news | vauthors = Gibson L |title=Is sunscreen from last year still good? When does sunscreen expire? |work=Mayo Clinic |url=https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/sunscreen-expire/faq-20057957 |url-status=live |access-date=June 22, 2018 |archive-url=https://web.archive.org/web/20201129195820/https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/sunscreen-expire/faq-20057957 |archive-date=November 29, 2020}}</ref>