I've recently gotten big into SPF(thank goodness!), but sometimes it makes my full coverage foundation oily and it changes color by the end of the work day. I was wondering: does a full coverage foundation count as SPF, or should I suck it up and put sunsreen on anyway?
For the second part of your question- no, a full-coverage foundation (without SPF) will not adequately protect you from the sun. If it does contain the SPF though, it will help, but most makeup only protects you from UVB. Make sure you are using a sunscreen that protects you from both UVA and UVB rays- the sunscreen will say it has SPF and PA+++ (anywhere from 1-3 +, 3 is the best protection) or it will be labeled as broad spectrum.
Does your foundation oxidize (change color) if you don't wear sunscreen underneath?
I'm glad you addressed the UVA issue -- I don't think many people are aware of this. Personally, I see SPF in makeup as an added bonus, but that is all; I would never rely solely on a foundation / powder's SPF, as it isn't meant be applied heavily enough (or even distributed evenly) to attain that protection level.
I suggest you wear a higher SPF- based moisturizer under your makeup, or even try an SPF powder you can dust on top of makeup! Those also double as a pretty good setting powder Better to be safe than sorry- I always feel like just wearing SPF on my makeup isn't enough so another layer can't help.
Algenist Ultra Lightweight UV Defense Fluid SPF 50
Peter Thomas Roth Instant Mineral Powder SPF 45