How many UVB rays does SPF100 allow through?

SPF15 lets about 7% of UVB rays, SPF30 lets around 3% through, and SPF50 about 2%. As for SPF100, this high sun protection factor allows around just 1% of UVB rays through. Now, although SPF100 sounds impressive, it is actually impossible to obtain technically – this is why the US forbids it to be advertised, says Dr Tina Meder, a dermatologist, cardiologist, and founder of Meder Beauty Science.

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