Sunscreen

UV filters

What's in sunscreen, and how does it work?

Active UV filters reduce how much UV reaches skin cells. Mineral and organic filters work differently but share the goal.

Active vs inactive

Actives are the UV filters. Inactives make it spreadable, stable and pleasant to use.

Mineral filters

Zinc oxide and titanium dioxide — mostly absorb UV, and scatter some.

Organic filters

Avobenzone, oxybenzone, octocrylene and others absorb UV and release it as small amounts of heat.

Application basics

The AAD recommends broad-spectrum, SPF 30 or higher, water-resistant sunscreen; about 1 ounce to cover an adult body; reapply every 2 hours or after swimming or sweating.

Absorption ≠ harm

Some filters are detectable in blood after use. The FDA states this does not mean they are unsafe and continues to recommend sunscreen use.

Evidence & sources

• Use broad-spectrum SPF 30+ sunscreen, about 1 oz for the body, reapplied every 2 hours. Evidence: strong. Known: Professional guidance consistent with clinical evidence that sunscreen reduces sunburn and some skin cancers. Unknown: How closely people apply the tested amount in real life. Source: American Academy of Dermatology, How to select a sunscreen / How to apply sunscreen (Current revision).

Connected topics

• Zinc Oxide
• Titanium Dioxide
• Avobenzone
• Oxybenzone
• UV Radiation
• Skin
• Hazard ≠ Risk

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General education only, not medical advice. Drafted Oct 2026 · pending qualified expert review.