SPF Ingredients Explained: Mineral vs Chemical
Understanding UV Filters
Sunscreen filters fall into two categories: mineral (physical) and chemical (organic). Both work by absorbing UV radiation and converting it to heat. The idea that mineral sunscreens only reflect UV is a myth.
Mineral Filters
Zinc Oxide
The broadest-spectrum filter available. Protects against UVA1, UVA2, and UVB. Non-irritating, safe for sensitive skin and babies. Downside: can leave a white cast, especially on deeper skin tones.
Titanium Dioxide
Strong UVB protection, moderate UVA2. Often combined with zinc oxide for complete coverage. Less white cast than zinc but less UVA protection.
Chemical Filters
Avobenzone (UVA)
The primary UVA filter in the US. Unstable alone, requires stabilization with octocrylene or Tinosorb. Photodegrades 50-90% in 1 hour without stabilizers.
Octinoxate (UVB)
Effective UVB filter, lightweight feel. Concerns about reef impact (banned in Hawaii). Also can degrade avobenzone if not properly formulated.
Octocrylene (UVB + UVA2)
Primarily a stabilizer for avobenzone. Mild UVB protection on its own. Low irritation profile.
Newer Filters (Approved in EU/Asia, Not US)
- Tinosorb S/M: Photostable, broad-spectrum, minimal skin absorption
- Uvinul A Plus: Excellent UVA protection, photostable
- Mexoryl XL: Patented formula, very stable
The Verdict
For sensitive skin: mineral (zinc oxide). For daily cosmetic elegance: newer chemical filters (if available). The best sunscreen is the one you will actually wear every day.
