K-Beauty Glossary
What is UVA vs UVB?
Two distinct UV wavelengths
UVA (320–400nm) penetrates deep into the dermis — causes aging, wrinkles, and contributes to skin cancer. UVA passes through glass and is roughly constant throughout daylight hours. UVB (280–320nm) is shorter wavelength, burns the skin surface, causes most sunburns, and peaks around noon. Modern SPF values primarily measure UVB; PA+++ ratings (Japanese/Asian) or PPD/UVA seals (EU) measure UVA. A sunscreen that says 'SPF 50' with no UVA indicator protects against burning but may not protect against aging.