PA value overview and content structure

PA value (Protection Grade of UVA) is an index that measures the protection ability of sunscreen products against long-wave ultraviolet rays (UVA). It is commonly seen on the labels of Japanese sunscreen products. Together with SPF value (protection against UVB), it forms a dual sunscreen system.This article will start from four parts: the definition of PA value, grading standards, practical applications and product recommendations. It will focus on analyzing its scientific principles and purchasing guides. Secondly, it will supplement the comparison of common products in the market to help readers fully understand sunscreen efficacy.

Definition and classification standards of PA value

The PA value is derived from the evaluation system developed by the Japan Cosmetic Industry Association (JCIA). The number of "+" symbols indicates the strength of protection: PA+ (effective protection), PA++ (quite effective), PA+++ (very effective), and some products are upgraded to PA++++ (ultra-high protection).The test is based on the delay time of persistent skin darkening (PPD) after UVA irradiation. For example, PA+++ represents a PPD value ≥8.It should be noted that European and American brands often use "Broad Spectrum" or "PPD" to replace the PA logo, but the protection principles are the same.

The relationship between PA value and daily sun protection

UVA has strong penetrating power and can directly reach the dermis layer, accelerating photoaging and wrinkle formation. Therefore, the PA value is particularly important for long-term anti-aging.It is recommended to choose PA++ or above for daily commuting, and PA+++ or above for outdoor activities, and reapply every 2 hours.Experimental data shows that PA+++ products can block about 90% of UVA, but the actual effect is affected by factors such as the amount of application and sweating, so you need to use a sufficient amount (about the size of a 1 yuan coin).

Comparison of mainstream PA sunscreen products in the market

Summary and scientific sun protection suggestions

PA value is the core parameter of sunscreen products against photoaging, and it needs to be selected comprehensively in combination with SPF value and usage scenarios.Authoritative dermatologist Dr. Zoe Draelos pointed out: "Sun protection requires both UVB and UVA. PA+++ and above can significantly reduce collagen damage." Consumers should avoid blindly pursuing high values ​​and pay attention to the ingredient ratio (such as zinc oxide, titanium dioxide and other physical sunscreen agents) and the compatibility with personal skin type.

Citing sources

1. Japan Cosmetic Industry Association (JCIA) "UVA Protection Test Standard for Sunscreen Products"
2. Research published by dermatologist Dr. Zoe Draelos in "Journal of the American Academy of Dermatology"
3. Source of market product data: Shiseido, Kao, and L’Oreal 2023 official product manuals