Zinc Oxide.

What it does

Beyond sun protection it doubles as a soothing skin protectant, which is why it shows up in everything from sunscreens to diaper and barrier creams.

Benefits

• Broad-spectrum UVA and UVB protection in a single, photostable filter
• Gentle, non-irritating, and non-comedogenic, great for sensitive skin
• Soothes and protects irritated skin (used in calamine and barrier creams)
• Works on contact and does not break down in sunlight

Side effects

• Can leave a white cast, especially non-nano grades on deeper skin tones
• May feel heavier or harder to blend than chemical sunscreen filters

Who it's for

All skin types, especially sensitive, reactive, or acne-prone skin wanting sun protection

Who should be careful

Avoid loose-powder or aerosol-spray forms where fine particles could be inhaled; topical creams and lotions on intact skin are considered safe