LEVEL 2
UV and Photoaging Science
When choosing sunscreen, you see labels like "SPF50" and "PA++++." But do you truly understand what these numbers and plus signs mean?
SPF (Sun Protection Factor) is a measure of protection against UVB (short-wave UV: 280-315nm). UVB primarily affects the epidermis and causes sunburn (redness/erythema).
SPF 30 means that the time it takes for UVB-induced sunburn to occur is extended 30 times compared to not wearing sunscreen. SPF 30 blocks approximately 97% of UVB, while SPF 50 blocks approximately 98%.
PA (Protection Grade of UVA) is a grading system for protection against UVA (long-wave UV: 315-400nm). UVA penetrates to the dermis and destroys collagen and elastin, causing wrinkles and sagging (photoaging).
There are four levels from PA+ to PA++++, with more plus signs indicating greater UVA protection. PA+++ or higher is recommended for daily use.
SPF50+/PA++++ isn't necessarily the best choice. Higher values tend to increase the burden on skin. For daily life, SPF 30-35/PA+++ is sufficient. Choose SPF50+/PA++++ for outdoor sports and leisure activities.
The most important thing is "applying the right amount correctly and reapplying frequently". No matter how high the SPF value, effectiveness drops significantly if the amount applied is insufficient. The recommended amount for the entire face is approximately 1g (about two pearl-sized drops).
KAIAN develops skincare products based on photoaging research.
Please feel free to contact us with any questions.
