Sunscreen, finally worth wearing

For years the case against wearing sunscreen every day was not really about risk. It was about texture: the chalk, the sting, the grey cast on deeper skin, the way it rolled off under foundation by eleven. Chemistry has dealt with most of that. What is left is a regulatory divide between markets and one honest weakness in daily use.

Sunscreen is the only topical intervention sold on a beauty counter with an evidence base that would satisfy a cardiologist. The Nambour trial in Queensland randomised more than sixteen hundred adults to daily sunscreen or to discretionary use and followed them for years afterwards. Squamous cell carcinoma fell. Melanoma fell in the long term follow up. In a separate arm, skin ageing measured by surface microtopography was significantly lower in the daily group. That is a randomised controlled trial with hard endpoints, which is not a sentence anyone can write about a peptide. The filter question is where geography matters. European and Asian formulators have had access to modern organic filters, bemotrizinol, bisoctrizole and the Mexoryl family, for roughly two decades. They deliver broad ultraviolet A cover at low concentrations, which is why a Korean or French formula can feel like a light moisturiser while an American one at the same stated factor feels like paint. The United States regulates sunscreen as an over the counter drug, and no new filter has completed that route since the 1990s. Repeated legislative attempts to unblock it have not yet produced an approval. The number on the front is measured at two milligrams per square centimetre, an application thickness almost nobody achieves. Field studies put real world application somewhere between a quarter and a half of that, and protection falls faster than proportionally as the layer thins. This is the practical argument for buying a high factor and applying it generously, rather than treating factor thirty as sufficient because a table says so. Ultraviolet A cover is the part the front label tends to hide: look for a PA rating, the circled UVA mark, or a stated critical wavelength.

Which leaves the failure point, and it is not the product. Almost every serious problem with daily use now happens after the first application of the morning, in the eight hours when nobody reapplies anything and the label quietly assumes they have.

Reapplication is the weak point and the industry has no good answer to it. The guidance says every two hours of exposure, which is straightforward on a beach and close to unworkable over a made up face at a desk. Powders carrying a stated factor are tested at an application weight nobody reaches with a brush. Sprays are worse, both for dose delivered and for what gets inhaled. Sticks are the most honest of the reapplication formats, dense enough to put down a real quantity, though they need more passes than most people give them. The sensible position is to be strict about the morning dose and honest about the rest. Two fingers' length for face and neck, applied as the last step before makeup, is the closest most people will come to the tested thickness. Reapply properly at midday if the day involves being outdoors. If it does not, accept that the morning application, with shade and a hat when they matter, is doing most of the work. Ordinary window glass blocks ultraviolet B and transmits a portion of ultraviolet A, which is worth knowing without becoming a source of anxiety for anyone sitting two metres from a north facing window. Texture is now a solved problem, which removes the last excuse. Japanese and Korean chemical formulas sit under foundation without pilling. European ones tend to be more emollient and suit dry skin through winter. Mineral filters have improved to the point that a tinted zinc formula can be worn on deeper skin without a grey cast, though untinted ones still cannot. Price correlates with texture, not with protection: a supermarket factor fifty tested to the same standard protects as well as one at four times the money. Buy on how it feels, because the one that feels acceptable is the one that gets used every morning, and that is the entire mechanism.