Roughly ninety percent of visible skin aging — fine lines, uneven tone, loss of elasticity, sunspots — is caused by ultraviolet exposure. That's not a marketing claim; it's the conclusion of decades of dermatology research. Daily sunscreen is the single most effective anti-aging product you can use, and most patients aren't using enough of it.

What to look for

• Mineral filters (zinc oxide, titanium dioxide). Sit on top of the skin, reflect UV, and tend to be better tolerated by sensitive or post-treatment skin.
• SPF 30 or higher. SPF 50 is fine; the difference between 30 and 50 is real but smaller than most people think.
• Broad spectrum. Protects against both UVA (aging) and UVB (burning).
• A texture you'll actually wear. The best sunscreen is the one you reapply.

How much, how often

A quarter-teaspoon for the face and another for the neck and chest. Reapply every two hours when you're outdoors, and after sweating or swimming. A morning application alone, sitting at a desk near a window, is meaningfully better than nothing — but not equivalent to a sun-protection plan if you're outside.

What it pairs with

Vitamin C in the morning before SPF amplifies your protection against environmental damage. A nightly retinoid undoes some of what the sun has already done. Together with daily SPF, those three steps outperform almost any boutique skincare line.