For this reason, European sunscreen guidance places particular importance on balanced protection against both UVB and UVA radiation. Manufacturers developing sunscreens or cosmetic products with sun protection claims should therefore evaluate UVA protection using appropriate and scientifically recognized testing methods.
What Is UVA Radiation?
Ultraviolet radiation from the sun is commonly divided into UVA and UVB radiation.
UVB radiation is strongly associated with sunburn and is the main type of radiation measured when determining the Sun Protection Factor, or SPF.
UVA radiation penetrates more deeply into the skin and contributes to premature skin ageing and long-term skin damage. It is also involved in processes associated with the development of skin cancer.
Unlike UVB radiation, UVA exposure does not always produce an immediate visible reaction such as sunburn. Consumers may therefore be exposed to significant UVA radiation without immediately noticing its effects.
This is why effective sunscreen products should provide protection across a broad range of the ultraviolet spectrum.
Why Is UVA Testing Necessary?
The SPF value alone cannot demonstrate the level of UVA protection provided by a sunscreen.
Two formulations with the same SPF may provide very different levels of UVA protection. The type of UV filters used, their concentrations, photostability, distribution within the formulation, and the film created on the skin can all influence UVA performance.
UVA testing provides measurable evidence of the protection delivered by the finished product.
Under Commission Regulation (EU) No. 655/2013, cosmetic claims should be supported by adequate and verifiable evidence. Therefore, manufacturers making UVA or broad-spectrum protection claims should hold appropriate testing data to substantiate those claims.
European Requirements for UVA Protection
The European Commission’s Recommendation 2006/647/EC establishes an important principle for balanced sunscreen protection.
The UVA protection factor should be at least one-third of the claimed SPF.
For example, a sunscreen labeled SPF 30 should provide a UVA protection factor of at least 10. A product labeled SPF 50 should provide a UVA protection factor of at least approximately 16.7.
The Recommendation also specifies that the critical wavelength should be at least 370 nanometres.
These criteria are intended to ensure that sunscreen products provide sufficiently broad protection across the UVA and UVB spectrum rather than concentrating protection primarily in the UVB range.
ISO 24443: In Vitro UVA Testing
One of the principal international standards used to evaluate UVA protection is ISO 24443:2021, Cosmetics — Determination of sunscreen UVA photoprotection in vitro.
This standard specifies an in vitro procedure for characterizing the UVA protection of sunscreen products. It is designed to generate a UV spectral absorbance curve from which relevant UVA protection parameters can be calculated.
During the test, a controlled quantity of sunscreen is applied to specially prepared test plates. The product is carefully distributed to create a representative film.
The transmission of ultraviolet radiation through the product layer is then measured using specialized laboratory equipment. The samples are also exposed to a defined UV dose to evaluate the product after irradiation.
The resulting spectral data is used to determine the in vitro UVA protection factor and assess the product’s UVA performance.
Because application technique, plate characteristics, irradiation conditions, and instrumental measurements can influence the result, the procedure should be performed according to the standardized methodology by an experienced laboratory. ISO 24443:2021 specifically establishes an in vitro procedure intended to characterize UVA protection and determine spectral absorbance characteristics reproducibly.
ISO 24442: In Vivo UVA Testing
UVA protection can also be evaluated using an in vivo method described in ISO 24442.
This method determines UVA protection on human participants by evaluating persistent pigment darkening caused by controlled UVA exposure.
The sunscreen is applied to defined areas of the skin. These areas are then exposed to carefully controlled UVA radiation, and the skin response is evaluated according to the standardized procedure.
The results are used to calculate the UVA protection factor of the tested product.
In vivo UVA testing requires carefully controlled study conditions, appropriate participant selection, and qualified personnel. For this reason, it should only be conducted by laboratories with suitable experience and ethical oversight.
What Is Critical Wavelength?
Critical wavelength is a measurement used to evaluate how broadly a sunscreen absorbs ultraviolet radiation.
It is calculated from the sunscreen’s UV absorbance spectrum. A higher critical wavelength generally indicates that protection extends further into the UVA range.
Under the European Commission’s sunscreen Recommendation, the critical wavelength should be at least 370 nm.
This requirement helps demonstrate that the sunscreen provides broad-spectrum protection rather than strong protection within only a narrow portion of the UV spectrum.
Critical wavelength should not be confused with UVA-PF. The two measurements provide different information and are used together when assessing the UVA performance of a sunscreen.
The UVA Circle Logo
Many sunscreen products sold in Europe display the letters “UVA” inside a circle.
This symbol is widely used to indicate that the product provides UVA protection in line with the European Commission’s recommended relationship between UVA protection and SPF.
The symbol should only be used when the product’s UVA performance is appropriately supported by testing.
Manufacturers should therefore ensure that the measured UVA protection factor meets the recommended minimum of one-third of the labeled SPF and that the relevant broad-spectrum criteria are satisfied before using UVA protection indications on the packaging.
Documenting UVA Test Results
UVA testing reports should be retained as part of the technical documentation supporting the cosmetic product.
The Product Information File, or PIF, must contain proof of the effects claimed for the cosmetic product where justified by the nature or effect of the product.
For a sunscreen making UVA protection claims, laboratory reports and supporting efficacy documentation help demonstrate that the claims presented to consumers are appropriately substantiated.
The documentation should clearly identify the tested product and the method used so that the results can be linked to the formulation placed on the market.
What Happens If a Product Fails UVA Testing?
A sunscreen may achieve its intended SPF but still fail to provide sufficient UVA protection.
For example, the measured UVA-PF may be below one-third of the SPF value or the product may not achieve the expected critical wavelength.
In such cases, manufacturers may need to reconsider the UV filter system, improve photostability, adjust the formulation, or review the claimed protection level.
After significant reformulation, the product should be tested again to verify its performance.
The Importance of UVA Protection in Sunscreen Products
UVA testing is a fundamental part of evaluating sunscreen performance in the European market. While SPF primarily measures protection against UVB radiation, UVA testing demonstrates whether a product also provides adequate protection across the longer ultraviolet wavelengths.
European Commission Recommendation 2006/647/EC recommends a UVA protection factor of at least one-third of the labeled SPF and a critical wavelength of at least 370 nm. International standards such as ISO 24443 provide standardized methods for evaluating UVA photoprotection in vitro.
For cosmetic manufacturers, UVA testing is not simply a laboratory formality. It provides the scientific evidence needed to support meaningful sun protection claims, maintain accurate product documentation, and offer consumers balanced protection against both UVA and UVB radiation.
