We all know that applying sunscreen before going outside is important for preventing skin damage — but how much sunscreen should you use? It turns out most people aren't putting on enough, and it's leaving them vulnerable, according to a new study.
In a 2018 study published in the journal Acta Dermato-Venereology, researchers from King's College London looked at whether changing the amount of sunscreen applied affected levels of skin damage. They divided 16 fair-skinned participants into two groups: One team was exposed to ultraviolet radiation (UVR) a single time, while the other group was exposed to UVR for five consecutive days to recreate conditions you might find while on a tropical vacation. The researchers treated areas of the participants' skin with high-SPF sunscreen in differing thicknesses.
The results found that participants who were exposed to UVR on consecutive days showed "considerable" skin damage on the areas that weren't protected from the sun — even though the UVR levels were low. When participants who were in the repeated-UVR-exposure group wore sunscreen at a thickness of 2 mg/cm2, they showed significantly less skin damage than the participants in the single-exposure group who were unprotected for just one day. Basically, that means participants who wore a thick enough layer of sunscreen for five days and were exposed to UVR showed less skin damage than participants who didn't wear sunscreen for just one day. Is that enough proof that not wearing sunscreen — even for one day — is dangerous?
So what's the takeaway here? Use sunscreen liberally! The researchers found that if participants applied sunscreen as they normally would, the amont of lotion they put on would provide only 40 percent of the protection they expected. Adults need to use at least an ounce of sunscreen to adequately protect their bodies, according to the American Academy of Dermatology. For reference, that's a full shot glass!
Another useful tidbit is to always go for a higher SPF. "In theory, an SPF of 15 should be sufficient, but we know that in real-world situations, we need the additional protection offered by a higher SPF," said Nina Goad, head of communications for the British Association of Dermatologists. "It also shows why we shouldn't rely on sunscreen alone for sun protection, but we should also use clothing and shade. An extra consideration is that when we apply sunscreen, we are prone to missing patches of skin, as well as applying it too thinly."
So the next time you're about to head out for a day at the beach or a family dip in the pool, make sure you put on plenty of sunscreen — and don't forget all those hidden spots, like behind the ears!