We all know products with SPF helps prevent sunburn, but does it truly protect against ageing UVA rays? A groundbreaking 8-lab international study tested 36 sunscreens to find out – here’s what matters for your skin: The Science Behind UVA Protection
A special lab test (using 1.2 J/cm² of UVA) reliably predicts real skin protection
Results matched human skin tests perfectly
This method is now the gold standard for measuring UVA defense
Why This Matters for You
THE COLIPA IN VITRO UVA METHOD: A STANDARD AND REPRODUCIBLE MEASURE OF SUNSCREEN UVA PROTECTION
P.J. Matts, V. Alard, M.W. Brown, L. Ferrero, H. Gers-Barlag, N. Issachar, D. Moyal, R. Wolber
BACKGROUND
While sunlight provides genuine benefits, there is no doubt that wavelengths in the ultraviolet radiation (UVR) waveband of the solar spectrum, comprising both ultraviolet B (UVB; 290–320 nm) and ultraviolet A (UVA; 320–400 nm) radiation, represent a significant risk in the aetiology of carcinogenesis and photoageing. UVA wavelengths also play a significant role in the damaging effects of UVR exposure, both acutely and chronically, as recent research suggests. OBJECTIVE To select a suitable unit dose of UVA (D0) for the SSR step, to take into account the important aspect of sunscreen photo-stability and, thus, achieve the closest possible agreement between in vitro UVAPF and in vivo UVAPF values (as determined by the PPD method). METHOD
Eight separate testing laboratories were involved and was divided into two ring studies.
The first study involved testing 24 commercially available sunscreen products, measuring their in vitro UV transmission.
The second study involved testing 12 commercially available sunscreen products using a standardised sunscreen film application on roughened PMMA plates and transmission measurement with a UV spectrophotometer.
RESULTS
A strong correlation between in vitro UVAPF values and in vivo UVAPF values was found.
A unit dose of 1.2 J cm-2 of UVA, when multiplied by a sunscreen’s pre-irradiation UVAPF0, gave the most accurate prediction of in vivo UVAPF (measured by the PPD method).
The study demonstrated that the in vitro method is a reliable and reproducible measure of sunscreen UVA protection.
CONCLUSION
This new in vitro method is a reliable, reproducible, and accurate way to measure UVA protection in sunscreen products.
The study confirms that the in vitro method provides a good prediction of in vivo UVAPF values as determined by the PPD method, which is important for consumer safety and product efficacy.
This information can help consumers make informed decisions about the sunscreen products they choose to use.
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