Photostable UVA/UVB Filtration
SPF values measure only UVB protection — the fraction of the UV spectrum responsible for sunburn, direct DNA strand breaks, and squamous cell proliferation. UVA radiation, comprising approximately 95% of UV reaching the Earth's surface at ground level, penetrates deep into the dermal layer, generating reactive oxygen species, degrading collagen cross-links, activating matrix metalloproteinases, and driving persistent pigmentation cascades. A sunscreen that is not independently tested for UVA protection via critical wavelength (≥370 nm) or persistent pigment darkening (PPD) ratio is providing structurally incomplete photoprotection — regardless of how prominently its SPF number is advertised. This distinction is the first filter to apply when evaluating any sunblock price in Pakistan.
