NMA: Nonprescription Medicines Academy

SPF: How High Is High Enough?

July 9th, 2009

With the advent of sunscreen products carrying sun protection factor (SPF) values of 70, 85, and even 100+, does higher equal better?

Not necessarily, according to a May 14, 2009, article in the New York Times (“Confused by SPF? Take a Number”). The article underscores some key points to keep in mind when advising patients about sunscreen.

No SPF—not even SPF 100+—offers 100% protection. And SPF indicates protection against UVB radiation only. Dermatologists recommend using a water-resistant sunscreen with an SPF of at least 15 that provides broad-spectrum protection from both UVA and UVB rays.
The difference in UVB protection between SPF 50 and SPF 100 is marginal—98% of UVB rays blocked vs 99%, respectively. SPF 30 blocks 96.7% of UVB rays.

Proper application is more important than an ultra-high SPF value. All sunscreens should be applied generously to all exposed skin and reapplied every 2 hours, even on cloudy days, as well as after swimming or sweating. “Generously” means that an adult wearing a swimsuit should use 1 oz of sunscreen—enough to fill a shot glass. At least one half teaspoon (an amount the size of a quarter) should be used on just the face and neck.

Author: Cynthia Knapp Dlugosz, BPharm
Date: June, 2009