SPF (Sun Protection Factor), which is the protection factor of sunscreen cosmetics, shows to which extent the natural skin protection mechanism is increased. For example, if the natural protection duration of your skin is 15 minutes, with a product with protection factor (SPF) of 3 this duration will be 3 times longer and become 45 minutes.
The sun protection factors act as a shield against UV rays on the skin through their chemical structures: the UVA filters put a wall against UVA rays that accelerate the skin aging process; the UVB filters stop UVB rays that cause sunburn.
The sunscreen product used needs to provide protection against both UVB and UVA. The SPF statement written on the sunscreens only provides information about UVB protection.
However, when UNDESIRABLEe effects, which are caused by UVA, are considered, it is very important to protect from UVA as well. Since 2006, Colipa (The European Cosmetic, Toiletry and Perfumery Association) has been recommending that the UVA value should be written on the packaging as well. In an effective sunscreen, the protection factor determined by the PPD (persistent pigment darkening) method should be more than 1/3 of the protection factor determined by the SPF test method.
Minimum Effectiveness Parameters
The minimum requirement needed for sunscreen products to have this characteristic is providing minimum level of protection against UVB and UVA rays. The degree of protection should be measured by standardized, repeatable test methods and photo-degradation must be considered. In vitro test methods should be given priority. The minimum level of protection provided by sunscreen products should be as follows:
• The sun protection factor (SPF) value obtained through the International Sun Protection Factor Test Method 2006 or any in vitro method should be 6 for protection against UVB.
• UVA having the 1/3 of the sun protection factor mentioned on the label should be achieved through the “permanent pigment darkening method” or with an equivalent level of protection in any in vitro method. • The critical wavelength of 370 nm obtained by implementing the critical wavelength measurement method.
Simple and Meaningful Effectiveness Claims
Claims indicating the effectiveness of sunscreen products should be simple, clear and meaningful and should be based on standardized and reproducible criteria. Claims indicating the UVB and UVA protection can only be written, if the value of the protection is equal to or above the values given under Article 6. The effectiveness of sunscreen products should be included on the label by referring to categories as “low”, “medium”, “high” or “very high”. Each category should correspond to the standardized protection degree against UVB and UVA rays. The diversity of numbers showing the sun protection factor on the labels will be simplified in a way to make it easier for the consumer to compare between different products and should be limited in a way not to diminish the consumer’s preference. Oral, figurative, or other markings used in sunscreen products cannot be used to imply characteristics which do not belong to the products. The range of sun protection factors and recommendations on labeling for each category are set out in Table 2.
SPF Measurement Method in-vitro
A special spectrophotometer, which is capable of measuring at intervals of 1 nm between 290-400 nm wavelengths, is used.
A special substrate with a rough surface called PMMA (polymethylmethacrylate) is used. The surface area should not be less than 16 cm2. (50x50x2.5 square is preferred).
Glycerine is used as a blank solution.
The product is applied on the substrate in a way to be 0.75 μg/cm2. Saturated gloves are used during application. Application is performed by pressing lightly for 30 seconds and then pressing firmly for the next 30 seconds.
UV transmission is measured before being exposed to any UV ray. The in-vitro SPF value is reached by using a specific coefficient.
If the incomplete UVAPF value calculated with the obtained transmission value is greater than 1/3 of the SPF value, the test continues. The substrate is exposed to UV rays. Then it is measured again. The in-vitro UVAPF is calculated by using the transmission value found.
UV-2000S Ultraviolet Permeability Analyser
Measurement parameters: İn vitro SPF, UVA/UVB oranı, kritik dalgaboyu
Lamb: Xenon flash lambası
Measurement Range: 250-450 nm dalgaboyu
Plate: PMMA HD-2
Surface area: 50×50 mm
Permeability: 0-100 %