Habit Hack: The Science of SPF – What You Need to Know for Optimal Sun Care
Understanding SPF Calculation
Sun Protection Factor (SPF) measures protection against UVB rays:
- SPF 15: Blocks 93% of UVB rays.
- SPF 30: Blocks about 97%.
- SPF 50: Blocks 98%.
- SPF 100: Provides up to 99% protection.
How Long Does SPF Allow You To Stay in the Sun
The duration of protection from your sunscreen depends on the SPF rating and other factors like your location, the time of day, and surrounding conditions.
An hour of morning sunlight might be less intense than 15 minutes of noon sunlight, and both are typically less harsh than just a few minutes near reflective surfaces at high altitudes.
Choosing the Right SPF for Your Skin
Selecting the appropriate SPF involves assessing several factors:
- Skin Reaction Time: Know how quickly your skin starts to change colour without protection.
- Expected Exposure: Consider whether you’ll be indoors, outdoors, or in intense midday sun.
- Environmental Factors: Reflect on the day’s UV intensity which can be higher in places closer to the equator or at higher altitudes.
For everyday use, SPF 30 to 50 is typically sufficient. For extended outdoor activities, especially in harsh sun conditions, opt for SPF 50+.
