Question: What's the difference between PPD and PA?
PPD and PA both measure how well a sunscreen protects against UVA rays. Because there is no international standard for this measurement, some countries use PPD (ex. PPD 20) and other countries use PA (ex. PA++). Most European sunscreens are measured in PPD and most Asian sunscreens are measured in PA.
The higher the number or the more plus signs there are, the better UVA protection you get from the sunscreen. Below are some approximations for the PPD equivalent of PA:
- PA+ = PPD 2-4
- PA++ = PPD 4-8
- PA+++ = PPD 8 and up
A sunscreen with a PPD of 8 and higher or a PA with three plus signs is great for everyday use. However, how protective it will be will still depend on the sunscreen's photostability, UV filters, and proper application.
To calculate the PPD of your sunscreen, check out this helpful website. You have to register, but it’s free.
To understand the difference between PPD and SPF, check here.
Last updated: September 25, 2012
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