For being an in vitro methodology, it does not implicate in exposing human beings to ultraviolet radiation, being a more ethical method and with a lower cost. The evaluation is carried by spectrophotometric methods and it comprises the product exposure to an ultraviolet radiation dose, being also possible to evaluate its stability.
ISO 24443 only predicts the UVA-PF calculation, but it also enables the use of absorbance data obtained through this method for the calculation of other photoprotection parameters, such as critical wavelength.
The critical wavelength represents the wavelength (nm) corresponding to 90% of the absorption spectrum integral between the wavelengths 290 and 400nm. The higher the critical wavelength, the wider the protection range provided the product is, meaning that it protects against radiations with longer wavelengths, within the ultraviolet spectrum. For sunscreen products, it is required a critical wavelength superior or equal 370nm.
The FDA methodology (2011) is currently the only one accepted in the U.S. and it comprises the evaluation of the protection against UVA radiation only by the determination of the critical wavelength, which also should be superior to 370nm. If the requirement is met, this methodology enables to score the protection provided by the product as being “broad-spectrum protection”.
Allergisa is accredited by the Cgcre (CRL 0669) to conduct the UVA-PF determination test and critical wavelength test according to ISO 24443 and also joins proficiency tests (interlaboratorial) for this method, assuring consistent results with international labs.
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