Does a higher SPF sunscreen provide better protection?
A lot has been written lately about sunscreens in the medical literature and the press. One comment you will read frequently is that there is very little benefit to an SPF (Sun protection factor) higher than SPF30. The basis behind this advice is scientifically sound.
Approximate UVB ray blockade:
SPF15 sunscreens block 93%
SPF30 sunscreens block 97%
SPF50 sunscreens block 98%
Looking at these figures, it would certainly seem reasonable to conclude, increasing SPF above 30 provides very little additional benefit.
However, standard SPF laboratory testing that dictates a sunscreens SPF rating is very different from how sunscreens are used in real life. Multiple studies have confirmed the fact that we do not apply our sunscreen anywhere near as thick as in the standardised SPF testing protocol (2 mg/cm2). When we apply our sunscreen at the beach, we are likely to be getting considerably less protection than the product provided in the laboratory setting. Therefore, using a higher SPF rated product will help cover the difference between testing and real-life usage.
This has now been proven in a December 2017 study published in the Journal of the American Academy of Dermatology. Nearly 200 people were randomised to apply a SPF50 sunscreen to one side of their face, and a SPF100 sunscreen to the opposite side of their face without knowing which was which. No advice was given as to the amount, or how to apply the sunscreen, so the experiment was closer to representing real-life usage. Independent and the subjects' own assessment of sunburn scores following sun exposure both showed significantly higher sunburn on the SPF50 side of the face compared to the SPF100 side.
There is also a second reason why a higher SPF sunscreen is likely to be more desirable. Broad-spectrum sunscreens (which are universally recommended as the best) can only be labelled 'broad-spectrum' when their UVA protection is at least 30% of the UVB protection (the SPF rating is based on UVB testing alone). UVA is a longer wavelength radiation present in the sun which has been implicated in both skin cancer and sun-damage to the skin. A higher SPF sunscreen therefore offers a higher UVA protection and therefore better broad-spectrum protection.
Sunscreens are only filters and do not block all of the sun's harmful radiation. They should be used in conjunction with other sun-protection behaviours such as seeking shade, using clothing and sunglasses, and keeping out of the sun in the middle of the day when the UV levels are at their highest. However, it seems higher SPF rated sunscreens do indeed offer increased protection when used in real life.