Introduction
Sunscreen products play an important role in protecting skin against ultraviolet (UV) radiation. For manufacturers, however, demonstrating the claimed level of protection requires scientifically robust, reproducible and appropriately standardised efficacy testing.
Traditionally, Sun Protection Factor (SPF) testing has relied substantially on controlled exposure of human volunteers to UV radiation to assess erythemal response.
The European Union is now moving toward greater use of in-vitro and non-invasive sunscreen efficacy testing.
A major development came in September 2026, when the European Commission published the results of an EU market-surveillance campaign comparing conventional in-vivo SPF testing with the newer EN ISO 23675:2024 in-vitro method. Seventy-four sunscreen and day-cream products from 11 EU countries were tested. The Commission reported a high correlation between the in-vitro and conventional in-vivo results and advised manufacturers to prioritise testing methods that do not expose human volunteers to UV radiation.
This development marks an important change in the way sunscreen efficacy may increasingly be demonstrated.
What Is SPF Testing?
Sun Protection Factor (SPF) is an indicator of the protection provided by a sunscreen against UV radiation responsible primarily for sunburn and erythema.
In practical terms, SPF testing evaluates the ability of a sunscreen product to reduce UV-induced erythema compared with unprotected skin. SPF claims commonly appear on products as:
- SPF 15
- SPF 30
- SPF 50
- SPF 50+
However, the number on the label should be supported by an appropriate, standardised testing approach.
The European Commission states that sunscreen efficacy claims should be based on standardised and reproducible criteria and that products should provide protection against relevant harmful UV radiation.
What Is UVA Protection?
UV radiation reaching the Earth’s surface includes both UVA and UVB radiation.
UVB
UVB is strongly associated with:
- Sunburn
- Erythema
- Direct DNA damage
UVA
UVA penetrates deeper into the skin and is associated with:
- Photoageing
- Oxidative stress
- Long-term skin damage
- Contribution to skin cancer risk
Therefore, a sunscreen assessment should not focus only on SPF.
A product can have a high SPF while providing inadequate UVA protection if the formulation does not provide appropriate broad-spectrum protection.
For this reason, SPF and UVA protection should be considered complementary aspects of sunscreen efficacy.Traditional In-Vivo SPF Testing
Conventional SPF testing has historically involved controlled exposure of human volunteers to UV radiation. The basic concept involves comparing the erythema response:
Protected skin vs Unprotected skin
The SPF is then calculated from the corresponding UV exposure required to produce a defined erythemal response.
The conventional approach has provided an established means of assessing sunscreen efficacy, but it has limitations.
Key limitations include:
- Requires human volunteers
- Exposure to UV radiation is necessary
- Volunteer skin characteristics can influence results
- Testing can be time-consuming
- Volunteer availability can limit testing
- Ethical considerations arise from deliberate UV exposure
The European Commission’s 2026 market-surveillance campaign specifically highlighted the ethical advantage of avoiding UV-induced sunburn in human volunteers.
The Shift Toward In-Vitro SPF Testing
A significant development is the availability of EN ISO 23675:2024, an in-vitro method for determining sunscreen SPF.
The standard was published in December 2024 and uses a laboratory-based approach that does not require UV exposure of human volunteers.
The method measures UV transmission through a controlled sunscreen film applied to specialised substrates.
The European Commission’s 2026 comparison found a high correlation between the in-vitro method and conventional in-vivo SPF results for the products assessed.
This provides important evidence supporting broader adoption of non-invasive sunscreen efficacy testing.How Does In-Vitro SPF Testing Work?
The in-vitro approach uses a controlled laboratory setup rather than human skin.
According to the European Commission’s description of the EN ISO 23675:2024 method, sunscreen is applied to two types of acrylic plates:
- A moulded plate
- A sandblasted plate designed to reproduce relevant surface characteristics
The application process is standardised.
Parameters such as:
- Amount of product applied
- Application technique
- Temperature
- Drying time
- Product film formation
are controlled.
A standardised robotic application system is used to produce a reproducible sunscreen film.
A spectrophotometer then measures how much UV radiation passes through the sunscreen layer.
The measured UV transmission is used in the calculation of the SPF.Why Is In-Vitro SPF Testing Important?
The move toward in-vitro testing has several potential advantages.
1. Avoids UV Exposure of Volunteers
The method does not require deliberately inducing UV-related erythema in human volunteers.
2. Improved Reproducibility
Laboratory conditions can be more tightly controlled than biological responses in human subjects.
3. Faster Testing
Laboratory testing can reduce some practical constraints associated with recruiting and managing volunteers.
4. Reduced Volunteer Dependence
Testing does not depend on the availability or skin characteristics of human subjects.
5. Potentially Lower Testing Burden
The European Commission notes that the in-vitro method is cheaper and faster than conventional human testing.
In-Vivo vs In-Vitro SPF Testing
The two approaches should not simply be treated as interchangeable without considering the applicable standard, product type and regulatory context.
What Did the 2026 EU Sunscreen Testing Campaign Show?
The European Commission reported the results of a market-surveillance campaign on 15 September 2026.
The campaign:
- Tested 74 sunscreen and day-cream products
- Involved market-surveillance authorities from 11 EU countries
- Compared conventional in-vivo SPF testing with the newer in-vitro method
- Used EN ISO 23675:2024 for the in-vitro assessment
The Commission reported a high level of correlation between the in-vitro and conventional in-vivo SPF results for the products assessed.
This evidence supports a broader shift toward testing approaches that can demonstrate sunscreen efficacy without exposing volunteers to UV radiation.
However, the campaign does not mean that every existing sunscreen testing requirement has automatically been replaced by EN ISO 23675:2024.
Manufacturers should determine the applicable testing strategy based on the product, claim, destination market and current regulatory/standardisation requirements.What About UVA Testing?
SPF primarily addresses UV-induced erythema and therefore should not be considered a complete measure of sunscreen performance.
UVA protection testing is also important for demonstrating broad-spectrum protection.
The European Commission’s sunscreen framework states that sunscreen products should provide protection against dangerous UV radiation and that efficacy claims should be based on standardised and reproducible criteria.UVA assessment may consider parameters such as:
- UVA protection factor
- Critical wavelength
- UVA/UVB protection balance
- Spectral absorbance
UVA In-Vitro Testing
A commonly recognised approach for in-vitro UVA protection assessment is based on ISO 24443, which determines UVA protection characteristics from the spectral absorbance of a sunscreen film.
The method can provide information relevant to:- UVA protection factor
- UVA spectral profile
- Critical wavelength
- Broad-spectrum performance
Unlike conventional SPF testing based on erythemal response, in-vitro UVA testing evaluates the optical behaviour of the sunscreen film across the relevant UV spectrum.
SPF and UVA Should Be Assessed Together
A modern sunscreen efficacy programme should consider both:
SPF → Primarily UVB/erythema protection
andUVA testing → UVA protection characteristics
A product intended to provide broad-spectrum protection should therefore have an efficacy-testing strategy that supports the relevant claims.
This is particularly important for products marketed with claims relating to:
- High UV protection
- Broad-spectrum protection
- UVA protection
- Anti-photoageing protection
- Daily UV protection
- Sensitive-skin sun protection
EU Regulatory Framework for Sunscreens
Sunscreens marketed in the European Union are regulated as cosmetic products under Regulation (EC) No 1223/2009 on cosmetic products.
Sunscreen efficacy claims are also addressed by the European Commission’s Recommendation on the efficacy of sunscreen products and the claims made relating thereto, adopted in 2006.The Recommendation addresses:
- Sunscreen efficacy
- Minimum protection expectations
- Claims
- Labelling
- Consumer information
- Application instructions
UV Filters and Product Safety
Sunscreen efficacy cannot be separated from ingredient safety.
UV filters used in EU cosmetic products must comply with the applicable requirements of the EU Cosmetics Regulation.The European Commission notes that UV filters must be assessed and authorised before use in sunscreen products.
Therefore, sunscreen compliance involves two distinct but related areas:
Ingredient Safety
Are the UV filters and other ingredients permitted and safe for the intended use?
Product Efficacy
Does the finished product provide the level of SPF/UVA protection claimed?
A product should satisfy both aspects.Sunscreen Testing Beyond SPF and UVA
A comprehensive sunscreen testing programme may involve more than SPF and UVA efficacy.
Depending on the product and claims, manufacturers may also consider:- Water Resistance
For products claiming water resistance, an appropriate validated testing protocol should be used.
- Photostability
Assessment of whether the sunscreen maintains its protective characteristics following UV exposure may be relevant.
- Stability
Testing can evaluate whether product quality and efficacy-related characteristics remain within specification throughout shelf life.
- Microbiological Quality
Relevant microbiological testing is important for cosmetic products.
- Preservative Efficacy
Where applicable, preservative efficacy/challenge testing can support product safety and quality.
- Packaging Compatibility
Packaging should be assessed for compatibility with the formulation and protection of the product throughout its intended shelf life.
Limitations of the Current In-Vitro SPF Approach
The move toward in-vitro SPF testing is significant, but it does not mean that every sunscreen product can currently be assessed using one universal in-vitro method.
The European Commission specifically notes that the current in-vitro approach cannot presently be applied to sunscreen sticks and powders. The Commission also identifies water-resistance claims as an area where further standardisation work is needed.
Therefore, manufacturers should assess:
- Product format
- Formulation
- Intended claim
- Applicable standard
- Destination-market expectations
- Available validated methods
before selecting the testing strategy.
Why Standardisation Matters
Sunscreen testing is highly sensitive to methodological details.
Important variables can include:
- Product application amount
- Film thickness
- Substrate characteristics
- Application technique
- Drying time
- Temperature
- UV source
- Spectral measurement
- Calculation procedure
- Instrument calibration
Small differences in methodology can influence reported efficacy values.
Standardised testing therefore helps improve comparability, reproducibility and confidence in sunscreen claims.Implications for Sunscreen Manufacturers
The European Commission’s 2026 findings may have several practical implications for manufacturers.
- Review Existing Testing Strategies
Manufacturers should review whether current SPF testing approaches remain appropriate for their products and markets.
- Evaluate In-Vitro Options
Where applicable, EN ISO 23675:2024 may provide a non-invasive alternative for SPF determination.
- Strengthen UVA Assessment
SPF alone should not be treated as the complete measure of UV protection.
- Align Claims With Evidence
Marketing claims should correspond to the level and type of protection demonstrated through appropriate testing.
- Maintain Technical Documentation
Testing reports and supporting evidence should be maintained as part of the product’s technical and safety documentation.
- Monitor Standardisation Developments
Sunscreen testing standards continue to evolve, particularly around non-invasive methods and additional product formats.
How Eureka Supports Sunscreen Testing
Eureka can support cosmetic manufacturers, sunscreen brands and product developers with analytical and efficacy-testing requirements related to sunscreen products.
Depending on the product, claim and applicable analytical scope, testing support may include:- SPF Testing
Assessment of sunscreen protection using appropriate standardised methodology.
- UVA Testing
Evaluation of UVA protection characteristics and relevant parameters.
- Product Quality Testing
Support for relevant cosmetic quality and safety testing programmes.
- Stability-Related Testing
Assessment of product performance and quality during development and shelf-life studies, where applicable.
- Regulatory Support Testing
Testing programmes designed around:
- EU cosmetic requirements
- Product claims
- Customer specifications
- Export-market requirements
- Product development needs
The appropriate testing method should be selected based on the product format, formulation, claim, target market and applicable standard.
Practical Sunscreen Testing Workflow
A structured testing programme can follow:
Define Product & Claims
↓
Identify Applicable EU / Destination-Market Requirements
↓
Review UV Filters & Formulation
↓
Select SPF Testing Method
↓
Select UVA Testing Method
↓
Assess Additional Claims
↓
Conduct Laboratory Testing
↓
Evaluate Results Against Applicable Criteria
↓
Substantiate Product Claims
↓
Maintain Technical Documentation
This approach helps manufacturers connect formulation development, efficacy testing and regulatory compliance.
Key Takeaways
- Sunscreen efficacy testing is evolving toward more standardised and non-invasive approaches.
- The European Commission's September 2026 market-surveillance campaign compared conventional in-vivo SPF testing with EN ISO 23675:2024 in-vitro testing across 74 products from 11 EU countries.
- The Commission reported a high correlation between the in-vitro and conventional in-vivo results for the products assessed.
- The Commission has advised manufacturers to prioritise testing approaches that avoid harmful UV exposure to human volunteers where appropriate.
- SPF and UVA protection represent different aspects of sunscreen performance.
- ISO 24443 is an important standardised approach for in-vitro UVA protection assessment.
- EU sunscreen products fall under the EU Cosmetics Regulation (EC) No 1223/2009.
- Sunscreen claims should be supported by standardised and reproducible efficacy evidence.
- In-vitro testing is not yet a universal solution for every sunscreen format; the European Commission specifically identifies limitations for sticks and powders.
- Water-resistance claims require appropriate testing and remain an area where further standardisation is relevant.
- Manufacturers should periodically review SPF/UVA testing strategies as standards and regulatory expectations evolve.
Frequently Asked Questions (FAQ)
1. What is SPF testing?
SPF testing evaluates the level of protection provided by a sunscreen against UV-induced erythema, commonly associated with sunburn.
2. What is in-vitro SPF testing?
In-vitro SPF testing determines sunscreen protection through laboratory measurement of UV transmission through a controlled sunscreen film rather than by deliberately exposing human volunteers to UV radiation.
3. What is EN ISO 23675:2024
EN ISO 23675:2024 is an in-vitro method for determining the SPF of sunscreen products. It uses controlled laboratory measurements of UV transmission through sunscreen films.
4. Is in-vitro SPF testing replacing all human SPF testing in the EU?
The EU is moving toward greater use of non-invasive methods, but this should not be interpreted as a blanket replacement of every existing in-vivo testing requirement. The applicable method depends on the product, claim, standard and regulatory context.
5. What is the difference between SPF and UVA testing?
SPF primarily evaluates protection against UV-induced erythema, while UVA testing evaluates the product’s protection characteristics against UVA radiation. Both can be important for substantiating broad-spectrum sunscreen claims.
6. What is ISO 24443 used for?
ISO 24443 provides an in-vitro approach for determining UVA protection characteristics of sunscreen products based on their spectral absorbance.
7. Can all sunscreen products be tested using the new in-vitro SPF method?
Not necessarily. The European Commission currently identifies limitations for formats such as sunscreen sticks and powders.
8. Why is in-vitro SPF testing considered more ethical?
It can determine SPF without deliberately exposing human volunteers to UV radiation to induce erythema, reducing the ethical concerns associated with conventional human SPF testing.
9. Does a high SPF automatically mean strong UVA protection?
No. SPF and UVA protection are different characteristics. A sunscreen efficacy programme should consider the specific UVA protection evidence supporting the product’s claims.
10. Can Eureka support SPF and UVA testing?
Eureka can support sunscreen and cosmetic manufacturers with appropriate SPF, UVA and related testing programmes, subject to the applicable product format, method, laboratory scope and regulatory requirements.
Official References
- Regulation (EC) No 1223/2009 on Cosmetic Products
- European Commission – Recommendation on the efficacy of sunscreen products and the claims made relating thereto (2006/647/EC)
- European Commission – Sunscreen Products
- European Commission – EU Moves to More Ethical Sunscreen Testing (15 September 2026)
- EN ISO 23675:2024 – Cosmetics — Sun protection test methods — In vitro determination of sun protection factor (SPF)
- ISO 24443 – Determination of Sunscreen UVA Photoprotection In Vitro
- ISO 24444 – Cosmetics — Sun Protection Test Methods — In Vivo Determination of Sun Protection Factor (SPF)
- SCCS Notes of Guidance for the Testing of Cosmetic Ingredients and Their Safety Evaluation, 12th Revision
- European Commission / SCCS – Scientific Opinions on UV Filters
Conclusion
Sunscreen efficacy testing in Europe is entering an important transition.
The publication of the European Commission’s September 2026 market-surveillance results provides supporting evidence for the wider use of in-vitro SPF testing, particularly the EN ISO 23675:2024 methodology, as a more ethical and efficient approach to demonstrating SPF performance.
At the same time, sunscreen compliance should not be reduced to a single SPF number.
A robust programme should consider:
Formulation → SPF → UVA Protection → Additional Claims → Product Stability → Regulatory Requirements → Technical Documentation
For manufacturers targeting the European market, keeping pace with the evolving standardisation landscape can help ensure that sunscreen claims remain scientifically supported, reproducible and aligned with current regulatory expectations.
