How Sunscreen Actually Works (Absorb vs Reflect)
The chemical vs mineral mechanism, minus the fearmongering.
Studies show mineral filters such as zinc oxide and titanium dioxide actually absorb most of the UV they block, scattering only a small fraction — not simply 'reflecting' it as often claimed.
Cosmetic chemists emphasize that both chemical and mineral sunscreens primarily work by absorbing UV; the old 'absorb vs reflect' split oversimplifies how mineral filters behave.
Questions we get a lot
How does sunscreen actually work?
Sunscreens use UV filters in two groups. Organic ('chemical') filters such as avobenzone absorb UV and release it as a small amount of heat. Mineral ('physical') filters — zinc oxide and titanium dioxide — mainly absorb UV and also scatter some. Both cut how much UV reaches living skin cells.
Do mineral sunscreens really just reflect UV?
Mostly no. While mineral filters do scatter some UV and visible light, research shows zinc oxide and titanium dioxide absorb the majority of the UV they block — much like chemical filters. The popular image of a mirror-like shield 'bouncing' rays off the skin is largely a marketing simplification.
Is chemical or mineral sunscreen more effective?
Both are effective when applied properly. The FDA recognizes broad-spectrum chemical and mineral sunscreens, and dermatologists say the best one is the broad-spectrum SPF 30+ you'll actually apply generously and reapply. Mechanism matters less than amount, coverage and reapplication.
r/SkincareAddiction: 'Do chemical sunscreens really 'soak in' while mineral ones just sit on top?'