First it’s important to understand how UV-rays affect the skin. UV-A penetrates the dermic layer of the skin causing it to darken and age prematurely, and UV-B rapidly affects the skin resulting in inflammation and redness. UV-ray protection products have been developed to combat these particular UV-rays.
SPF is short for “Sun Protection Factor”. It’s a measure of how well a product protects the skin from sunburn (reddening from sun exposure) caused by UV-B. The greater the factor, the greater the sunburn protection.
PA is short for “Protection Grade of UVA”, and is an index that is primarily used in Japan. It indicates how well a product protects the skin from UV-A, which causes the darkening of the skin (Persistent Pigment Darkening), and the more “+” it has, the greater its UV-A protection.
PA+ Effective
PA++ Quite effective
PA+++ Very effective
PA++++ Extremely effective
It’s important to choose products that provide the appropriate SPF and PA protection based on your level of exposure to UV-rays.