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Outline
The Basics of Sun Protection Factor
How to Calculate the SPF?
Answers to SPF Value Misunderstandings
Testing Methods of SPF
Impact of Sunscreen Ingredients on SPF Value
Sunscreen Product Supervision in Various Countries
UVB, which is medium-wavelength ultraviolet light (280-320 nm), can cause sunburn and erythema on the skin. Sun Protection Factor (SPF) is a measure of a sunscreen's ability to prevent sunburn caused by ultraviolet (UV) B radiation. It tells you how much longer the skin with a sunscreen will be protected from sunburn than the skin without sunscreen. For example, an SPF 30 sunscreen theoretically provides 30 times more protection than no sunscreen.
The SPF value is determined by applying 0.4 ounces or 2 mg/cm2 of sunscreen to the skin, then shining artificial UVB light on the skin, measuring the time to minimum erythema on the protected and unprotected skin, and determining the SPF value.
Common sunscreen products on the market usually have three values: SPF 15, SPF 30 and SPF 50.
SPF 15: This is the fact that this sunscreen has a limit on erythema for 15 × 15 = 225 minutes. In other words, if used correctly, SPF15 sunscreen can prevent 1/15 of UVB rays from reaching the skin, which means it can block (1 - 1/15) × 100% = 93.3% of UVB.
SPF 30: This means that this sunscreen product can prevent the appearance of erythema for 15 × 30 = 450 minutes, and can block (1 - 1/30) × 100% = 96.6% of UVB.
SPF 50: Similarly, it can prevent the appearance of erythema for 15 × 50 = 750 minutes, and can block 98% of UVB.
No!
In terms of the SPF rating, as we saw above, SPF 50 gives only 1.3% more UVB protection than SPF 30, not 1.7 times! So too with the extra UVB protection offered by SPF values above 50, and SPF 100 offers not even double the UVB protection of SPF 50, but just about 1% more.
On the other hand, products with high SPF values generally have more sunscreen ingredient per unit amount which can leave your product greasier and heavier as well as irritate the skin to cause acne and blackheads. As a professional cosmetic formulator, you should take this into consideration.
No. Because the SPF value only measures the protection against UVB rays, that is, it is only the sunburn protection index, and cannot measure the degree of suntan protection. It is the UVA rays that tan the skin.
Alfa Chemistry's cosmetic testing laboratory has the ability to test and develop sunscreen formulas. Welcome to contact us to discuss your sunscreen product testing or R&D project.
The ingredient in sunscreen, how much you use it, and the formulation of the product can affect a product's SPF. Alfa Chemistry has listed out a few typical ingredients and how they may affect SPF for you.
Since there is an ever-growing worldwide sunscreen market, people are becoming much more concerned about the quality, safety and effectiveness of sunscreens. Countries have imposed their own testing procedures and standards to keep sunscreens safe and effective.
The United States, China, Japan, the European Union and other countries and regions all use human testing methods to determine the SPF value of sunscreen products. Although these methods are roughly similar, there are slight differences in subject selection, irradiation dose, and evaluation criteria. For example, the European Union uses the ISO 24443 standard, while Japan uses the method of the Cosmetic Industry Association (JCIA).
Moreover, there are ingredient testing and safety testing to ensure that it does not have toxic substances and follows all the regulations and standards. For instance, sunscreen ingredients testing in China mostly uses GB/T 35916-2018 to quantitatively define approved sunscreen agents and other UV-blocking substances in cosmetics. Tests for safety on sunscreens - toxicology, microbiology, etc. test the products to make sure that the product is free of toxic materials.
If you have any questions, please contact us. You will get a satisfactory answer.
