First, look at the active ingredients to determine whether it’s a chemical or mineral sunscreen.
Never make assumptions from the packaging alone. The Alba Botanica Fragrance Free Sunscreen Lotion SPF 40 above looks like it should be mineral, based on the name (“botanica” implies “natural”) and the fact that the brand does sell other non-chemical sunscreens. But this one is not—it actually contains more chemical filters than most (homosalate, octinoxate, octocrylene, octisalate and avobenzone). So you always have to inspect the ingredients
The next thing to do is check whether you see zinc oxide on the label.
Titanium Dioxide Only
Don’t buy any sunscreen that only contains titanium dioxide!
That’s because titanium dioxide alone gives you just partial protection against UVA rays, so it’s not truly broad-spectrum. It can protect you from a sunburn, but won’t do enough against the longer UVA wavelengths that cause premature aging.
Zinc Oxide Only
or Zinc Oxide + Titanium Dioxide/Encapsulated Octinoxate
As far as I’m concerned, zinc oxide is essential. Until we get the European filters Tinosorb M and Tinosorb S approved in North America, zinc oxide is the best filter we have and the ONLY one that offers complete UVA and UVB protection.
Look for zinc oxide alone, or in combination with titanium dioxide or encapsulated octinoxate. (Cyberderm’s Every Morning Sun Whip SPF 25 is the only product I know of using the encapsulation technology, which makes it as safe as a mineral.)
Your next step is to check what percentage of zinc oxide is in the formula.
Less Than 15 Percent Zinc Oxide
I would avoid any sunscreens that are less than 15 percent zinc oxide. At that low of a concentration, the UVA protection is likely to be insufficient.
Here’s how it works. Every one percent of zinc oxide gives you 1.6 SPF units. That means a 15 percent zinc oxide formula is only about SPF 24, which would be the bare minimum—ideally, we want to aim for SPF 30!
Even lower is the new Biologique Recherche Protection U.V. SPF 25 above. With only 3.8 percent zinc oxide and 2.5 percent titanium dioxide, it works out to about SPF 12, with seriously inadequate UVA protection! Shocking from such a revered skincare brand.
15 to 20 Percent Zinc Oxide
If you see a figure between 15 and 20 percent zinc oxide, it should ALSO contain another sunscreen filter—either titanium dioxide or the encapsulated octinoxate—in at least a 7.5 percent concentration. This will get you to a true SPF 30, with sufficient UVA protection.
20 Percent or More Zinc Oxide
Any sunscreens with 20 percent or more zinc oxide will give you complete UVA and UVB protection. Hooray!
The higher the zinc oxide level, the higher the SPF. So if we go back to that 1.6 SPF units calculation, 20 percent zinc works out to SPF 32.