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Photostability doesn’t get the attention it deserves in sunscreen development, and that’s a problem, because it quietly determines whether a product actually does what its label promises after an hour in the sun. In plain terms, photostability is a UV filter’s ability to hold its chemical structure and keep absorbing UV radiation once it’s been …

Photostability in Mineral Sunscreen Formulation: Challenges and Solutions Read More »

In Vitro vs In Vivo SPF Testing: What Formulators Actually Need to Know  I’ve been watching the ALT-SPF conversation play out since the consortium published its 2025 results in the International Journal of Cosmetic Science, and I keep seeing the same misunderstanding repeated across formulation forums, conference panels, and brand briefs: the idea that in …

In Vitro vs. In Vivo SPF Testing: Methods, Tradeoffs, and What’s Changing Read More »

There’s a conversation I’ve had more times than I can count, usually somewhere between the stability chamber and a looming launch deadline. A brand comes in with a W/O emulsion they’re proud of — nice skin feel, elegant finish, high zinc loading — and they want to label it “waterproof.” Sometimes they’ve already printed the boxes. That conversation never gets easier. Water resistance is …

Sunscreen Water Resistance Testing: ISO 16217, FDA Protocol, and What Formulators Need to Know Read More »