I thought it might be worth summarising some of the material I have found while researching UVA and UVB protection. The SPF rating you see on sunscreen is measured by reviewing the UVB protection offered by sunscreen, largely due to skin reddening (technically known as erythema). SPF ratings tell you how much longer you can stay in the sun to prevent sunburn.
UVA on the other hand causes DNA damage and is related to higher rates of melanoma, albeit this relationship is not full understood yet. To find a suncreen that offers UVA protection you need to look for broad spectrum suncreen ingredients. Often it’s written as PA+ or PA++. (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.)
L’Oreal (and many brands in the L’Oreal family) use Ecamsule, which has been sold in Canada and Europe for a long period but only had approval in the last 5-6 years for use in the US. It is a highly photostable UVA filter, and EWG calls it low risk which gets a huge tick from me.
Avobenzene is also commonly used in broad spectrum sunscreen, but this can be an issue as it’s protective abilities degrade over the time spent in the light as well as combining with iron to sometimes stain clothes … which isn’t excellent from things like sitting in old pool chairs 😦 Clinique, Aveeno and Neutrogena are combining avobezene and oxybenzone for a more stabilised UVA sunprotection. Some of the ‘off brands’ I checked in my local chemist that said they offered broad spectrum sunscreen only had avobenzone or zinc oxide. Oyybenzone can be a little irritating and triggers skin irritations in some of my family.
Anyway, when you see that a sunscreen offers broad spectrum sunscreen it’s a good idea to check what the active ingredients are and see whether it is a photostable sunscreen (doesn’t degrade in light). The other thing to remember is the SPF relies on you using a certain amount of sunscreen (about 1/3 teaspoon on your face), so if you use you makeup more sparingly than that amount you will need to combine your makeup with a sunscreen to get adequate sun protection.