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What is SPF?

SPF stands for Sun Protection Factor. It measures how long you’re protected from UVB rays, which cause sunburn.​

  • Example: If your skin burns in 10 minutes without sunscreen, SPF 30 theoretically gives you 30 × 10 = 300 minutes of protection (but reapplication is still necessary).

  • Higher SPF offers slightly more protection, but no sunscreen blocks 100% of UV rays — for example, SPF 30 blocks about 97% of UVB rays, while SPF 50 blocks around 98%.

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Chemical vs. Mineral Sunscreen

Chemical Sunscreen:

  • Absorbs UV rays and converts them into heat to be released from the skin.

  • Contains ingredients like avobenzone, oxybenzone, or octinoxate.

  • Usually feels lighter and blends easily into the skin.

  • Requires 20 minutes to activate after applying.

Mineral Sunscreen:

  • Sits on top of the skin and physically blocks UV rays.

  • Uses natural minerals like zinc oxide or titanium dioxide.

  • Ideal for sensitive skin, babies, and acne-prone skin.

  • Works immediately after application but may leave a slight white cast.

Broad Spectrum vs. Water-Resistant

  • Broad-spectrum means the sunscreen protects against both:

    • UVA rays (cause skin aging and some cancers)

    • UVB rays (cause burning and most cancers)

  • Water-resistant doesn’t mean waterproof. It lasts 40 or 80 minutes when sweating or swimming, then must be reapplied.

How Much & How Often Should I Apply?

  • Use the “One Ounce Rule” – about 1 oz of sunscreen for your full body.​

    • Also, use the "Three Finger Rule" – about 3 fingers of sunscreen for your face and neck.

  • Don’t forget ears, neck, top of feet, and scalp.

  • Reapply every 2 hours or after sweating/swimming.

  • Use daily—even on cloudy days or in winter.

    • Many people think you don’t need to wear sunscreen indoors, but you do because UVA rays can penetrate through windows and still damage your skin over time.

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