Today I got a question about sun block and which is the most natural and most effective one to use. Here's what I said:
I like zinc oxide the best because zinc oxide is known as "non-chemical" because it acts as a physical blocker to protect against UV radiation. The zinc oxide molecule is too large to pass through the skin's pores and so the zinc oxide remains on the surface of the skin. Zinc oxide would probably be the perfect sunscreen ingredient if the resulting product wasn't thick, white and pasty, it's the stuff seen mostly on lifeguards, surfers, and others who need serious sun protection. You will soon be seeing a new type of sunscreen on the shelves if you haven't already. You will find nanotechnology being incorporated into your sunscreens. When zinc oxide sunscreens are made with nanoparticles they actually turn clear (rather than white) - which makes them more user-friendly. Nanotechnology involves drastically shrinking and fundamentally changing the structure of chemical compounds. But the problem is, skin products made with nanomaterials raise a largely unanswered safety question - such as whether the particles that make them effective are small enough to be absorbed into the bloodstream and become toxic to living cells.
Titanium dioxide is also considered a "non-chemical" blocker but titanium dioxide is photoactive – it can react with sunlight to create chemicals known as free radicals. The structure of these atoms or molecules renders them highly chemically reactive, meaning they can attack the sunscreen itself, breaking it down and rendering it less effective. They could also damage the body's cells if they manage to pass through the skin barrier.
Long story short...I'd stick with the pasty, white zinc oxide.