New FDA regulations on sun protection
In the past, many people would put forward sunscreen instructions for American brands, such as why there is no PA instruction on the product, or why the product originally contains UV-protective sunscreen ingredients, but the package does not have UV-protective sunscreen instructions.
First of all, because the PA label is a Japanese standard, and the United States does not require it to be used, it is normal to not indicate the PA value on the product. As for the second point, the United States previously suggested that the UVA protection label can be labeled “Broad spectrum”) Protection) The detailed definition is as follows: The UVR absorption spectrum of the preparation is measured, and the critical wavelength is calculated using the Diffey method.
According to Diffey, the critical wavelength is the wavelength at which the absorbance curve is below 90%, while the critical wavelength of 370 nm or greater defines a “broad spectrum” sunscreen.
(Critical wavelength standards are difficult to understand.
The higher the critical wavelength of a sunscreen, the better its UVA performance relative to its UVB performance.
The critical wavelength is the upper limit of the spectral range starting at 290 nm, in which it covers 90% of the area under the extinction curve of the entire UV range between 290 nm and 400 nm.
The critical wavelength method requires mathematical integration of the in vitro product absorption spectrum from 290 to 400 nm to determine the wavelength at which the cumulative area of the 90% absorption curve is located.
) In short, the critical wavelength is above 370nm before it can be called broad-spectrum. However, this definition is really difficult for consumers to understand, and it is not very easy to calculate. Therefore, the FDA has always wanted to set a new standard in the UVA detection labeling part.
The plan began in 1999 and was finalized in 2007. In the end, it did not directly adopt the Japanese PA value or the European PPD value. It also abandoned the practice of simply indicating a broad spectrum and adopted the “star rating system” (a total of 1-4 stars).Such a new regulation can be described as a major breakthrough by the FDA in addressing sun protection directives. From the point of view of a dermatologist, it is really optimistic. Its comprehensive view has two main implications. (1) FDA’s protection against UVA (2) FDA’s UVA protection test considers both in vitro and in vivo tests (PA and PPD values are in vivo tests; critical wavelengths are in vitro tests)