Does a high SPF really protect better than SPF 30?
SPF 100+ protects better than SPF 50+ in genuinely sunny conditions, but always check the UVA label on the packaging as well, because the SPF number does not cover that protection.
SPF 100+ demonstrably protects better than SPF 50+ during beach use. In a randomised, double-blind study of 55 people, 56% of participants developed more sunburn on the side treated with SPF 50+, compared with only 7% on the SPF 100+ side. Furthermore, the first redness appeared on the SPF 50+ side after just one day, whereas on the SPF 100+ side this did not occur until three days later.
The SPF number says nothing, however, about protection against UVA radiation. SPF measures almost exclusively how well a product blocks UVB. UVA contributes to skin ageing, possibly to immune suppression, and perhaps to skin cancer as well, but it is tested separately and in a less standardised way. If you also want UVA protection, you need to look specifically for a broad-spectrum product carrying a separate UVA certification.
There is also a practical problem: the number on the packaging is less reliable than it appears. Research into 44 commercial sunscreen products showed that the same product could be classified as SPF 30, SPF 50 or SPF 50+ in different laboratories, with coefficients of variation exceeding 50%. The actual protection value of two products carrying the same number can therefore differ considerably.
Using broad-spectrum sunscreen regularly reduces the risk of actinic keratosis and a specific type of skin cancer (squamous cell carcinoma), and slows skin ageing. For melanoma and basal cell carcinoma, that benefit has not yet been demonstrated in the available studies. Finally, at the recommended quantity of 2 mg per cm² of skin, sunscreen inhibits vitamin D production. Because most people apply a thinner layer, this effect is smaller in practice than in laboratory tests.
Claims based on a randomised split-face study (n=55, PMID 31542406), an analytical study of 44 products (PMID 27079525), and multiple review studies on UVA protection, skin cancer prevention and safety (PMID 11705089, 25207381, 16113595).
Is an expensive face cream better than a cheap one?
A higher price does not make a face cream more effective or safer. It is better to pay attention to the ingredient list than to the price tag or marketing claims on the packaging.
Does sunscreen also protect against skin ageing?
Sunscreen demonstrably protects against sun-related skin ageing, including wrinkles, age spots and loss of skin texture. Daily use of a broad-spectrum sunscreen is the best-supported choice for this purpose.
How much sun is safe, and does the tanning bed really cause skin cancer?
Tanning beds genuinely cause skin cancer: the evidence is causal and strong. Short, regular sun exposure is beneficial for vitamin D, but burning must be avoided at all times.
Does omega-3 protect your skin from sunburn?
Omega-3 may offer some protection against sunburn reactions, but the evidence from good studies is too limited and no proven protective dose is known. Simply continue using sunscreen and regard omega-3 at most as a possible supplement.
Does resveratrol really help protect cells against ageing?
Resveratrol protects cells impressively in the lab, but whether that holds true in your body is uncertain: the body breaks the substance down quickly and large studies in people are largely absent.
Can you repair sun damage to your skin?
Sun damage can be partially repaired: prescription tretinoin cream has the strongest evidence base, but consistent sunscreen use is the prerequisite for any repair programme.