Sandbox:Sara

Measurement of UV protection afforded by sunscreens and clothing

Measurement system	SPF (Sun protection factor)	UVA‐PF (UVA‐protection factor)	UPF (Ultraviolet protection factor)
Definition	Minimal erythema dose (MED) of UVB radiation causing erythema after applying 2 mg/cm2 of sunscreen to skin divided by the dose producing 1 MED on unprotected skin	The dose of UVA causing observable pigment darkening (minimal pigment dose [MPD]) after applying 2 mg/cm2 of sunscreen to skin divided by the dose producing 1 MPD on unprotected skin	The ability of fabrics to prevent UV radiation transmission via absorption and/or reflection and highly dependent on fabric type, color, porosity, thickness, weight, and other factors
Developed for	Sunscreens	Sunscreens	Clothing
Global acceptance	International	United States only	International
UV wavelengths protected	UVB	UVA	UVA, UVB
Examples	SPF 2 protects against 50% of UVB SPF 8 protects against 88% of UVB SPF 15 protects against 93% of UVB SPF 30 protects against 97% of UVB SPF 50 protects against 98% of UVB	UVA‐PF1 protects against 20–39% of UVA UVA‐PF2 protects against 40–69% of UVA UVA‐PF3 protects against 70–95% of UVA UVA‐PF4 protects against >95% of UVA	UPF cotton 5–10 UPF denim 1700

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Mohsin, M.D.[2]