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Sun Protection Factor

Description

Sun Protection Factor (SPF) is a crucial measure in sunscreen formulations, indicating the level of protection against ultraviolet B (UVB) rays. It quantifies how much longer skin covered with sunscreen can be exposed to sunlight before burning, compared to unprotected skin. SPF works by incorporating active ingredients that either absorb or reflect UV radiation. Common chemical filters include avobenzone, octinoxate, and oxybenzone, while physical blockers typically use zinc oxide or titanium dioxide.

Higher SPF numbers offer greater protection, but the relationship is not linear. SPF 30 blocks about 97% of UVB rays, while SPF 50 blocks approximately 98%. It's important to note that SPF primarily addresses UVB protection and doesn't necessarily indicate UVA coverage. Broad-spectrum sunscreens are formulated to protect against both UVA and UVB rays.

Effective use of SPF products requires proper application and reapplication. Generally, 1 ounce (30 ml) is needed to cover the entire body, and reapplication should occur every two hours or after swimming or excessive sweating. While higher SPF products offer marginally better protection, consistent and correct use of any SPF product is more critical for skin health.