What Makes a Filter 'Broad-Spectrum'?
The label term that matters more than the SPF number.
Because SPF measures only UVB, the US requires a critical-wavelength test (370 nm or higher) before a sunscreen can be labeled 'broad-spectrum.'
Dermatologists emphasize that broad-spectrum is the more important label than the SPF number, because SPF alone says nothing about the UVA that drives aging — and newer broad-spectrum filters such as bemotrizinol retain roughly 98% of their activity even after intense UV exposure.
Questions we get a lot
What does broad-spectrum protection actually mean?
'Broad-spectrum' means a sunscreen protects against both UVA and UVB. In the US a product must pass an FDA critical-wavelength test to make the claim. Because SPF only measures UVB protection, broad-spectrum labeling is how you know you're also covered against deeper, aging UVA rays.
Why are some UV filters more photostable?
A photostable filter keeps absorbing UV without breaking down in sunlight. Older filters like avobenzone can lose protection within an hour unless paired with stabilizers such as octocrylene. Next-generation broad-spectrum filters are engineered to stay chemically stable, so protection lasts longer — though reapplication is still advised.
What is bemotrizinol (Parsol Shield)?
Bemotrizinol (trade name Parsol Shield; also known as Tinosorb S) is a broad-spectrum UVA+UVB filter that is highly photostable. On June 9, 2026 the FDA approved it — the first new sunscreen active added to the US monograph since the 1990s — for adults and children 6 months and older at up to 6%.
r/AsianBeauty: 'What does broad-spectrum actually mean, and how do I check for it?'