How do I know which sunscreen to use?

Let's start with what are UVA and UVB:

UVA is rays of light that penetrate deeper into the skin and can cause longer term damage which can lead to wrinkles, age spots, and an increased risk of skin cancer.

UVB rays penetrate the skin more shallowly which can cause sunburns and can contribute to an increased risk of skin cancer.

How do we block UVA and UVB damage and what is the difference between SPF and the PA system of sunscreens?

First off SPF stands for Sun Protection Factor and it protects against UVB rays. This system is common in the United States and is graded with numbers 1-100.  SPF 30 is commonly recommended for protection against sunburns as it protects you up to 97%.  SPF 50 is the preference of many estheticians as it protects against sunburns at a rate of 98%.

The PA system rates the Protection Grade of UVA and is most common in Europe and Asia. This system uses a “+” as an indicator of UVA protection levels. PA+ = some, PA++ = moderate, PA+++ = high, and PA++++ = very high levels of UVA protection. PA+++ and PA++++ are the preferred levels of protection by estheticians to prevent and slow related skin damage.

“Broad Spectrum” sunscreens should provide some protection against both UVA and UVB damage, but without both the SPF and PA listings it is not entirely clear how much damage for either type of radiation is being protected against, so be sure when looking at sunscreens that your bottle shows both systems for optimal protection.  In the United States the PA system is not generally used and many of our filters do not have much protection against UVA.  The two best US filters for UVA are zinc oxide and/or avobenzone, so when looking at a broad spectrum sunscreen in the US, if it doesn’t have a PA marking, look for high levels of these two filters.