A:
The term SPF refers to the ability of a sunscreen to block ultraviolet B (UVB) rays, which cause sunburns, but not UVA rays, which are more closely linked to deeper skin damage. Both UVA and UVB contribute to the risk of skin cancer.
An SPF 15 product blocks about 94% of UVB rays, an SPF 30 product blocks 97% of UVB rays, and an SPF 45 product blocks about 98% of rays.
Finding a sunscreen that adequately protects against UVA rays is much trickier, but every bit as important. UVA radiation reaches deeper into the skin and contributes to wrinkles and skin cancer risk. Nearly all (95%) of the UV radiation that we are exposed to is UVA radiation.
Sunblock vs. Sunscreen
The major difference between sunblocks and sunscreens is that sunblocks are mineral based (always) and sit on the surface of the skin. The active ingredients are zinc oxide and titanium dioxide. Sunscreens are generally chemical based and must be absorbed into the skin to be effective via a chemical reaction with the UV rays. Ingredients vary widely, as does their safety.
Zinc Oxide is sometimes referred to as the only safe sun protection available in a tube. It protects from the full spectrum of UVA and UVB rays, incredibly effectively, all by itself, making it truly the best natural sunscreen ingredient available. It is a sun block, and sits on the surface of your skin forming a barrier between you and the rays of the sun.
Historically, zinc oxide sunblocks are notoriously difficult to rub in. Your skin ends up looking a little ghostly white from the sunblock. It's a different look and can be a tricky transition if you've been used to spray sunscreen or lotion that's super easy to rub in until it disappears. However, science and technology have come a long way and there are a number of physical sunblocks on the market that do not leave a white chalky film on the skin.
So my recommendation is: wear an SPF 15 or 30 that contains zinc or titanium oxide on your face EVERY DAY. If you are going to be out in the sun wear an SPF 30 (zinc or titanium oxide) and re-apply throughout the day. Always remember to bring your sunscreen down our neck and onto your chest. Also, remember to apply sunscreen to your hands.
