A study published online October 12, 2026, in the Journal of the American Academy of Dermatology argues that the long-standing 0.5 ng/mL plasma threshold — the line regulators use to decide whether a sunscreen ingredient warrants further safety testing — deserves a second look in the era of bemotrizinol.

The paper, titled "Beyond the 0.5 ng/mL Threshold: Reframing Maximal Usage Trials After Bemotrizinol," comes from Mackenzie K. Joe, Ananya Sampathkumar, Anita Prabhu, Cathryn Bigham, Alexander J. Jafari, and Carina A. Wasko.

The 0.5 ng/mL benchmark has framed sunscreen-safety debate since the FDA applied it in its 2019–2020 maximal usage trials (MUsT). Under that framework, any active ingredient whose plasma concentration exceeds 0.5 ng/mL after maximal application triggers additional toxicology work — including carcinogenicity and developmental studies — before the agency considers it generally recognized as safe and effective (GRASE).

Six organic filters tested under that program — avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate — all cleared the threshold in the blood, some within hours of a single application. None has since gained GRASE status. Only zinc oxide and titanium dioxide carry that designation today.

Why bemotrizinol changes the conversation

Bemotrizinol, a broad-spectrum UV filter already approved in Europe and other markets under names such as Tinosorb S, has become the leading candidate to fill the US filter gap. It absorbs across both UVA and UVB wavelengths and shows strong photostability.

The new JAAD paper's central argument, as its title signals, is that the binary logic of the 0.5 ng/mL line may not fit what maximal usage trials actually measure. The authors propose reframing how these trials are designed and interpreted after bemotrizinol's data — an argument that speaks directly to whether the US sunscreen market can finally absorb modern filter chemistry.

That's a live regulatory question. The FDA has not approved a new UV filter since 1999, even as consumers in the EU and Asia access formulations with newer, more photostable ingredients.

What does this change for dermatologists?

For clinicians, the stakes are practical. If maximal usage trial interpretation shifts, the pathway to US availability for bemotrizinol — and the reformulation of daily-use sunscreens that dermatologists recommend for skin-cancer prevention and photodamage — could widen considerably.

The paper arrives at a moment when sunscreen access and safety messaging are under active policy discussion, and its authors — spanning contributors with clinical and regulatory-relevant affiliations — position it as a data-first intervention in that debate.

Whether regulators move on the framework, and how quickly bemotrizinol's US file advances under any revised interpretation, will shape the next chapter of American photoprotection.