I have talked about the difference between SPF and PA systems for the sunscreen but yet star rating system. Today, let's go deeper into the star rating system and see what it means.

As SPF is for UVB rays, and PA for UVA rays, then, what is the boots star rating system for? The boots star rating system is for measuring how much UVA is blocked. So, is the PA system the same as the boots star rating system? The answer is NO. Though the boots star rating system indicates the protection level of the sunscreen that offers in the UVA spectrum, it's not a direct rating to classify the strength of protection toward the UVA rays. So, how does it work? The difference between SPF and PA

The Star rating system measures the sun protection level by testing whether the sunscreen evenly protects the skin throughout the UV light spectrum. To put it simply, if the protection level of the sunscreen toward UVA and UVB is almost equal, the star rating would get a 5. If the sunscreen is less capable to block UVA than UVB, the star rating would be lower.

For 3 stars, it means that the UVA/UVB ratio is between 0.6 to 0.79.

For 4 stars, the UVA/UVB ratio is between 0.8-0.89.

As for 5 stars, the UVA/UVB ratio is between 0.9 and even higher.

Now you know, it is not enough to judge the protection level of sunscreen only by star rating. What if the UVA protection level and UVB protection level of a sunscreen are evenly low? In this case, it can still get a 5-star rating. So, in general, the sunscreen product out there would mark both SPF number and star rating. Contact us!