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How does sunscreen work?

Medicine & HealthLesson on requestFree to read

Quick answer

Sunscreen works by blocking or absorbing the sun's ultraviolet (UV) rays before they damage your skin. Mineral sunscreens reflect UV away, while chemical sunscreens soak it up and release it as harmless heat. UV radiation from the sun damages skin cells and DNA, causing burns, aging, and cancer risk.

Step by step

  1. UV radiation from the sun damages skin cells and DNA, causing burns, aging, and cancer risk.
  2. Mineral (physical) sunscreens use zinc oxide or titanium dioxide to scatter and reflect UV.
  3. Chemical sunscreens absorb UV and convert it into a small amount of heat.
  4. SPF measures protection against UVB (burning) rays; 'broad spectrum' adds UVA protection.
  5. It wears off, so reapplying every couple of hours — and after swimming — matters.

People also ask

What does SPF mean?
Sun Protection Factor — roughly how much longer protected skin resists UVB burning versus bare skin. SPF 30 blocks about 97% of UVB; higher numbers add only a little more.
What's the difference between mineral and chemical sunscreen?
Mineral sunscreens sit on the skin and reflect UV; chemical ones absorb UV and release it as heat. Both work well when applied generously and reapplied.
Why do I need to reapply sunscreen?
It breaks down in sunlight and rubs or washes off, so protection fades. Reapply roughly every two hours and after swimming or sweating.