Understanding daily sun protection.
A practical guide to SPF, UVA/UVB, application and reapplication — written for daily use, not just beach days.
What SPF means
SPF measures how much a sunscreen extends the time before UVB rays cause visible redness, versus unprotected skin, under lab test conditions. It's primarily a UVB measure.
UVA vs UVB
UVB is more associated with surface-level burning and varies by season and time of day. UVA penetrates deeper, stays fairly consistent year-round, and passes through window glass.
Understanding PA++++
PA ratings indicate a sunscreen's UVA protection level in many regions, with more plus signs indicating a higher rating. Pairing an SPF rating with a PA rating signals broad-spectrum coverage.
Why daily sunscreen matters
Incidental daily UV exposure — commuting, sitting near windows — adds up over time. Dermatological guidance generally favors a daily habit over occasional, high-exposure-day use.
How much sunscreen to apply
SPF is tested using a specific, generous application amount. Under-applying is one of the most common reasons real-world protection falls short of the label. [INSERT VERIFIED APPLICATION QUANTITY GUIDANCE]
When to reapply
General guidance suggests reapplying roughly every two hours during continued exposure, and after swimming, sweating or toweling off.
Sunscreen and makeup
Sunscreen is generally applied as the last step before makeup. Reapplying over makeup can be done with touch-up formats designed for that purpose. [INSERT VERIFIED PRODUCT-SPECIFIC GUIDANCE]
Sunscreen for oily skin
Texture matters — a lighter, lower-shine gel format is often easier to wear consistently on oily or acne-prone skin than a heavier formula.
Sunscreen for daily urban life
Urban environments bring a mix of UV exposure and other environmental stressors, which is part of why antioxidant-paired sunscreens have become a common daytime category.
Visible light education
Beyond UVA and UVB, visible light and infrared exposure are areas of ongoing skincare research. [INSERT VERIFIED RESEARCH SUMMARY WITH CITATIONS]
Antioxidants and photoprotection
Antioxidant ingredients are typically formulated to complement, not replace, sunscreen's UV-filtering role.