UVA protection and the PA system: the rating that matters as much as SPF but appears on far fewer products

UV spectrum overview: what UVA and UVB do differently to skin

The UV spectrum relevant to skincare spans two ranges. UVB (wavelength 290–320 nanometres) is the short-wavelength, high-energy UV that is primarily responsible for sunburn, direct DNA damage in keratinocytes (the cyclobutane pyrimidine dimers that are the primary UV mutation) and the skin reddening (erythema) that the SPF rating measures. UVA (wavelength 320–400 nanometres) is the longer-wavelength, lower-energy UV that penetrates more deeply into the skin (reaching the dermis rather than primarily the epidermis), drives the photo-oxidative aging (reactive oxygen species generation, MMP activation, collagen fragmentation) that is the primary mechanism of visible photoaging, stimulates immediate tanning (through melanin redistribution), and contributes to skin cancer through indirect DNA damage mechanisms. UVB is the burning radiation; UVA is the aging radiation. The SPF rating on a product measures only UVB protection — leaving UVA exposure completely uncommunicated to the consumer by the SPF number alone.

How the PA system works and what the plus signs mean

The PA rating system (PA+, PA++, PA+++, PA++++) was developed in Japan and is widely adopted in Korea, China, Taiwan and other Asian markets. It measures UVA protection through the persistent pigment darkening (PPD) test — exposing a section of skin treated with the sunscreen and an untreated section to UVA and measuring the minimum dose required to produce persistent skin darkening (as opposed to the immediate darkening reaction, which measures a different cellular mechanism). The PPD ratio (treated skin dose divided by untreated skin dose) translates to the PA+ rating: PPD 2–4 = PA+, PPD 4–8 = PA++, PPD 8–16 = PA+++, PPD 16 or above = PA++++. PA++++ provides sixteen or more times the UVA protection of unprotected skin — the highest consumer-grade UVA protection rating available. A product labelled SPF50+ PA++++ covers the full UV spectrum at the highest protection level communicated by the Japanese-Korean PA system, which is the most rigorous consumer UVA rating system globally.

PDRN UV protection cream: why SPF50+ and PA++++ in the same formula matters

A PDRN UV protection cream with SPF50+ PA++++ provides the complete UV protection profile — high UVB blocking (SPF50+ absorbs approximately ninety-eight percent of UVB) and maximum UVA protection (PA++++ at PPD 16 or above) in a single formula. The PDRN component adds cellular repair signalling (adenosine A2A activation) that operates during and after UV exposure, addressing the UV-driven DNA damage and reactive oxygen species that the sunscreen filters reduce but do not eliminate (no sunscreen absorbs one hundred percent of UV). The combination of UV filtration (reducing UV that reaches the skin) and PDRN repair activation (repairing the effects of the UV that still reaches the skin despite filtration) provides more complete photoprotection than either UV filtration or repair activation alone.

Comparing Asian SPF to Western SPF: why the labelling differences matter for consumers

A significant labelling difference exists between Western and Asian sunscreen communication that affects how consumers assess their protection. In Western markets (EU, US), "broad spectrum" indicates that UVA protection meets a minimum threshold relative to the SPF value, but the specific UVA protection level is not communicated numerically. In Asian markets using the PA system, the exact UVA protection category is printed on the label, allowing direct comparison between products. A Western "SPF50 broad spectrum" product may have very low UVA protection (meeting only the minimum threshold) or very high UVA protection (equivalent to PA++++) with no way to distinguish from the label. An Asian market product with SPF50+ PA++++ communicates both UV dimension ratings explicitly. For consumers choosing between sunscreen products, the explicit PA rating on Korean and Japanese products provides more complete protection information than the same information available from Western "broad spectrum" labelling.

Building PDRN UV protection into a routine alongside rice cream hydration

The morning routine sequence that integrates PDRN UV protection cream and rice cream most effectively: apply the rice cream as the penultimate step (providing ceramide support, niacinamide and rice antioxidants, finishing with a comfortable emollient layer), then apply the PDRN UV protection cream as the final step (SPF and PA filtration last, as applied over all other products to maintain an uninterrupted UV filter layer on the skin surface without another product applied over it that could disrupt the filter distribution). The "sunscreen last" rule applies to all filter formulations: applying anything over a sunscreen can physically disrupt the even distribution of the UV filter matrix, reducing the effective SPF and PA protection below the label values. Rice cream under PDRN UV protection cream provides the hydration and barrier support base with the UV protection layer on top, maintaining the label-value protection level throughout the morning.