Verification Methods for "Full-Spectrum Protection": How to Prove Comprehensive UVA/UVB/HEV Coverage?

"Full-Spectrum Sun Protection" — A Claim Being Overused

Open any sunscreen product page in 2026, and claims like "full-spectrum protection," "blocks 99% of UV rays," or "blue light defense" are everywhere. But where do these numbers come from? What methods were used to measure them? Are the testing standards behind them consistent?

These questions rarely receive answers on most brands' promotional pages.

In February 2026, the Cosmetic Evaluation Center of China's National Medical Products Administration updated the Guiding Principles for Efficacy Claim Evaluation of Sunscreen Cosmetics, while the China Fragrance, Flavor & Cosmetic Industry Association concurrently released the group standard Guidelines for Sensory Evaluation of Sunscreen Products. This marks China's sunscreen industry officially entering an era of "strict regulation where efficacy claims must be evidence-based." Understanding the testing logic behind "full-spectrum protection" is a lesson both consumers and brands need to learn.

I. The Wavelength Landscape of Full Spectrum: UV Is Not the Whole Story

In technical contexts, "full-spectrum protection" must cover at least the following wavelength ranges:

Band	Wavelength Range	Primary Damage	% of Surface-Reaching Light
UVB	280–315 nm	Sunburn, erythema, direct trigger for skin cancer	~5%
UVA II	315–340 nm	Tanning, photoaging, synergistic factor for skin cancer	—
UVA I	340–400 nm	Deep dermal damage, core band for photoaging	~95%
HEV (High-Energy Visible Light / Blue Light)	400–500 nm	Accelerated pigmentation, oxidative stress	Part of visible light

UVA combined accounts for approximately 95% of total UV radiation reaching Earth's surface

II. UVB Protection Verification: SPF Measurement Methods and Limitations

ISO 24444: The International Gold Standard for In Vivo SPF Determination

ISO 24444 is the most widely adopted in vivo SPF testing standard globally, with China's GB/T 39502-2020 highly aligned with it.

Testing Procedure: Select ≥10 healthy adult subjects (Fitzpatrick skin types II–III), apply 2 mg/cm² of the test product to the back, expose to different doses of UV radiation using a solar simulator, and read the Minimal Erythema Dose (MED) after 24 hours.

SPF = MED of protected skin ÷ MED of unprotected skin.

Core Limitations:

• The standard test application amount is 2 mg/cm², but actual consumer usage is typically only 1/4 to 1/2 of this amount, resulting in actual protection being only 20%–50% of the labeled SPF value. In other words: a product labeled SPF 50 may provide protection equivalent to only SPF 10–25 under real-world usage conditions.

ISO 23675:2024 (Dual-Plate Method) & ISO 23698:2024 (HDRS Hybrid Method): A New Era of In Vitro Testing

Traditional in vivo methods (ISO 24444) require UV exposure on human subjects, posing ethical risks, high costs, and long cycles. In 2024, two new in vitro testing standards were officially released:

1.ISO 23675:2024 (Fully In Vitro Dual-Plate Method): Apply sunscreen samples to PMMA (polymethyl methacrylate) artificial roughened plates, measure spectral transmittance using a spectrophotometer, and calculate SPF and critical wavelength. Requires no human subjects, shows good correlation with in vivo results, and is the most recognized in vitro alternative under European regulations.

2.ISO 23698:2024 (HDRS Hybrid Diffuse Reflectance Spectroscopy Method): Combines in vivo + in vitro approaches—the UVA portion is measured via non-invasive spectral scanning on human skin using a Diffuse Reflectance Spectrometer (DRS, without damaging UV exposure), while the UVB portion uses in vitro PMMA plate measurement. A single test simultaneously yields three data points: SPF, UVA-PF, and critical wavelength. This is currently regarded as the most comprehensive and efficient sunscreen testing method; SGS officially announced the commercial launch of testing services under this standard in October 2025.

III. UVA Protection Verification: PA Values, UVA-PF, and Critical Wavelength

Two Mainstream Verification Pathways

In Vivo Method (ISO 24442): Similar human testing to ISO 24444, but the endpoint is the Minimal Persistent Pigment Darkening Dose (MPPD) rather than erythema—i.e., the critical dose at which slight visible tanning is observed 3–6 hours after UVA exposure.

In Vitro Method (ISO 24443): Measures transmittance in the UVA wavelength range using a spectrophotometer, using "Critical Wavelength (λc)" to assess UVA protection breadth—a critical wavelength ≥370 nm is required to claim broad-spectrum UVA protection.

Conversion Between PA Values and UVA-PF

EU regulations require: UVA-PF must be at least 1/3 of the SPF value to claim UVA protection and use the UVA protection symbol. Japan's JCIA adopts the PA rating system (PA+ to PA++++), corresponding to UVAPF ranges: PA+ = UVAPF 2–4; PA++ = 4–8; PA+++ = 8–16; PA++++ = ≥16.

The United States is the only major market that does not require UVAPF determination, only requiring calculation of "critical wavelength"; a critical wavelength ≥370 nm allows labeling as "Broad Spectrum".

IV. HEV Blue Light Protection: Most Claims, Most Chaotic Verification

Blue Light Protection Is a Genuine Need

High-Energy Visible Light (HEV, 400–500 nm), while not UV radiation, has been confirmed by recent research to: penetrate skin to the dermal layer (deeper than UVA), induce Reactive Oxygen Species (ROS) generation, accelerate melanin deposition (especially in darker skin tones), and potentially accelerate photoaging processes.

The Reality Dilemma of Blue Light Protection Verification

The lack of a universally recognized international standard is the biggest problem for blue light protection claims. As of 2026:

• There is no international testing standard for HEV protection equivalent to ISO 24444

• Brands typically use spectrophotometers to measure product spectral absorption in the 400–500 nm range, but testing methods, sample preparation, and data processing vary widely—"92.5% blue light protection rate" and "99% blue light protection" may come from entirely incomparable testing protocols

• China's current Cosmetic Efficacy Claim Evaluation Regulations do not yet specify standardized in vitro testing method requirements for HEV protection

How consumers can assess the credibility of blue light protection claims:

1. Does the product disclose the testing institution name and report number (e.g., SGS, CTI, China Cosmetic Testing, etc.)?

2. Does it specify the exact test wavelength range (full 400–500 nm or only a single peak wavelength)?

3. Does the test sample application amount comply with the standard 2 mg/cm² dosage?

2026 Real-World Case: One sunscreen product passed authoritative SGS testing, demonstrating 92.5% blue light protection rate and 99.2% effective full-spectrum sun protection (Special Cosmetics Registration No.: G20211625)—this is currently one of the more transparent cases for blue light protection claims on the market, providing both certification number and testing institution.

V. Compliance Baseline for Full-Spectrum Protection Claims

Current Chinese Requirements

China's Cosmetic Efficacy Claim Evaluation Regulations (implemented May 2021) stipulate:

• SPF value claims: Must be verified through human efficacy testing or equivalent alternative testing

• PA value claims: Must provide UVA-PF testing evidence

• "Broad-spectrum protection" claims: Must provide test data showing critical wavelength ≥370 nm

• Specific numerical claims (e.g., "blocks 99% of UV rays"): Must be verified by third-party CNAS/CMA-certified institutions, with efficacy evaluation reports submitted in filing materials

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Identifying Common Non-Compliant Claims

Consumers should be alert to the following types of claims:

• "Full-spectrum protection" claims without testing institution names or report numbers

• Products claiming blue light protection but not specifying testing methods or institutions

• "Protection lasting over X hours" claims without supporting data on sustained protection decay testing

• Significant discrepancies between UVA-PF values and SPF values (e.g., SPF 50+ but only PA++), which do not meet the scientific rationale of the EU requirement "UVA-PF ≥ SPF/3"

Summary

"Full-spectrum protection" is an efficacy claim that requires item-by-item verification across wavelength bands:

• UVB protection relies on SPF (ISO 24444)

• UVA protection relies on UVA-PF/PA values (ISO 24442/24443) and critical wavelength

• HEV blue light protection currently has no unified international standard and represents the dimension with the most claims and least transparent verification

The ISO 23698 HDRS hybrid method released in 2024 integrates the measurement of three core indicators into a single test for the first time and was commercially launched by SGS in October 2025—this represents the most significant methodological breakthrough in the field of sunscreen efficacy verification in the past decade and is gradually reshaping industry testing and claim standards.