How dangerous are Zinc Oxide nano-particles to the skin??? I'm sorry ahead of time if this is the wrong place to put this. I'm just curious if anyone here knows if nano-particles of zinc oxide sunscreen actually harms the skin??? Would it speed up photoaging (considering that it is effective in blocking UVA rays, which cause photoaging)?? I've seen conflicting reports, so I wanted to know what people here thought. Thank you so much.