The Myth About SPF Ratings
The sun protection factor (SPF) rating given to sunscreens tells us how well that product protects us against those wavelengths of the sun’s ultraviolet radiation that cause our skin to become red. There is a widespread misconception that sunscreens with SPFs over 30 provide a minimal increase in sun protection and are therefore not worth using since they are often thicker, more expensive, and less cosmetically pleasing than sunscreens with a lower SPF.
Although this is admittedly a controversial subject, there are now two studies showing that sunscreens with higher SPFs are more protective than sunscreens with lower SPFs, even when comparing sunscreens with SPFs ranging from 50-100. Until recently, only one study by Russell et al showed that sunscreen with an SPF of 85 was more effective in preventing sunburn than a sunscreen with an SPF of 50 in patients who were high altitude skiing.
The latest attempt to address this issue is a study performed on 199 male and female skiers and snowboarders in Vail Colorado. Study participants applied Neutrogena Ultra Sheer Dry-Touch Sunscreen broad spectrum SPF 100+ to half of their faces and necks, and applied Banana Boat Sport performance broad spectrum SPF 50+ to the other half of their faces and necks while skiing or snowboarding during the course of one day. They were instructed to apply sunscreen as they normally would while skiing and were then evaluated for facial redness the following day. Over 55% of participants were more sunburned on the SPF 50+ protected side as compared to 5% being more sunburned on the SPF 100+ protected side. There was no difference in sunburn severity in about 40% of people. This led to the conclusion that under actual use conditions, SPF 100+ sunscreen was significantly better than SPF 50+ sunscreen at protecting against sunburn.
Can Sunscreen Decrease Skin Cancer?
We know that sun exposure is responsible for photoaging, the formation of pre-cancerous growths and skin cancers, and for causing or exacerbating skin diseases induced by the sun. Sunburn is a physical sign of significant ultraviolet light damage to the skin. It is estimated that proper long-term use of sunscreen decreases the chances of having skin cancer by 50% to 75%.
We now have another study showing there is a clear benefit to using sunscreens with a higher SPF. Even when comparing high SPF sunscreens ranging from 50 to 100, higher SPF rated sunscreens were better at preventing sunburn and presumably the other negative effects of sun exposure. This is particularly relevant since studies show that in general, people apply only 1/3 to 1/2 the amount of sunscreen required by the FDA during testing done to assign an SPF rating to a particular sunscreen. This means that in real life situations, the most protection you can hope for is about half of the SPF listed on the label of the sunscreen you are using.
Therefore, when you are in the sun, I recommend wearing sun protective clothing and hats, using the highest SPF rated sunscreen you can, and reapplying that sunscreen every two hours to help maintain its effects.
Williams JD1, Maitra P1, Atillasoy E1, Wu MM1, Farberg AS2, Rigel DS3. SPF 100+ sunscreen is more protective against sunburn than SPF 50+ in actual use: Results of a randomized, double-blind, split-face, natural sunlight exposure clinical trial. J Am Acad Dermatol. 2018;78(5):902-910.e2.
Linden KG. Commentary: Sunscreen sun protection factor (SPF): Is higher better? J Am Acad Dermatol. 2018;78(5):911-912.. Epub 2018 Mar 13.
Russak JE, Chen T, Appa Y, Rigel DS. A comparison of sunburn protection of high-sun protection factor (SPF) sunscreens: SPF 85 sunscreen is significantly more protective than SPF50. J Am Acad Dermatol. 2010;62(2):348-349.