Does a sunscreen in face creams and makeup actually work throughout the day?

It's a common knowledge that you have to reapply your sunscreen every 2-3 hours for it to work. But if you apply a face cream with a spf only once under your makeup in the morning, how is it supposed to work whole day long? The same with the spf in makeup?Does a sunscreen in face creams and makeup actually work throughout the day?
I'm no scientist, but I can't imagine it working as effectively as real sunblock, of course. The SPF in make-up is usually 10-15, whereas conventional sunblocks are 45-50.. so right there you are losing a ton of effectiveness. You wouldn't really want to lay out on a beach all day in 10 SPF makeup and expect not to get burnt. If anything, I think it's more of a ';something's better than nothing'; thing. If you really are worried about it, try mixing a higher SPF sunblock in with the cream.





I also have to imagine that make-up in itself is blocking out at least some of the sun's damaging rays, I mean.. it's covering your face up, so that might actually help somewhat.





I think mostly what makes sunblock lose it's effectiveness throughout the day is splashing around in water, being exposed to the sun for prolonged amounts of time and laying out in a hot sun and sweating it off, however.. So in all reality, yes, I think a low SPF make-up foundation should last you throughout the day.. as long as your normal day-to-day activities don't include sweating or swimming..





These are really only speculations, but, figured I'd give your question a shot anyway. (: