@gymrat Is the vitamin c serum something you should work up to using every day? I've applied it 3 days in a row so far, but now I'm noticing that my skin looks darker, despite my zinc oxide sunscreen that leaves a white cast! Could this be due to irritation? I also read something about skin turning an orange-ish color if the serum doesn't fully absorb. I guess it can oxidize on the surface of the skin, which causes the orange color. Have you ever heard of this happening?