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When it comes to protecting our skin from the harmful effects of UV radiation, sunscreens are a must. However, how do we determine if a sunscreen delivers on its promises? The answer lies in rigorous testing. In this blog, we’ll explore how sunscreen’s protection factors, such as SPF, are evaluated, ensuring the efficacy of these vital products.
What does SPF mean?
SPF, or Sun Protection Factor, is the measure of a sunscreen’s ability to protect the skin from UVB rays, the type of radiation that causes sunburn and contributes to skin cancer. But SPF isn’t a straightforward number; its effectiveness depends on proper application and adherence to testing standards.
In Vivo Testing: The Standard for SPF Measurement
Nowadays, the SPF values are determined through in vivo testing, where the sunscreen is applied to the skin of human participants under controlled conditions. A specific area of the skin is exposed to UVB radiation, and the MED Comparison is made: The Minimal Erythema Dose (MED) — the smallest UV dose that causes redness — is measured with and without sunscreen.
The ratio of these MEDs provides the SPF value. For example, an SPF 30 sunscreen allows about 1/30th of UVB rays to reach the skin compared to unprotected exposure.
This method, the in-vivo one, is the only standard accepted to label a product, as it is the real application of the product to the skin, checking the real efficacy of the product protection.
In Vitro Methods: A Growing Alternative
While in vivo testing is the gold standard, in vitro methods are increasingly used to measure UVA and UVB absorption with laboratory instruments. This provides consistent results without involving human volunteers, also ensuring UVA protection, that is not measured at the in-vivo SPF test.
Regulatory bodies and international organisations in regions like the EU emphasize in vitro tests to support animal-free and ethical research. Last month, Cosmetics Europe’s Double Plate Method (DPM) (ISO 23675:2024) was published and officially recognised as an International Standard Organisation (ISO) Standard by the ISO Central Secretariat. Experts from the suncare products and ingredients industry led another in vitro method, the hybrid method catalogued as ISO 23698. Both methods have undergone extensive work during their development to ensure their correlation with in vivo assessments using ISO 24444.
This means that the DPM and the hybrid method will be two in vitro alternatives to test the Sun Protection Factor (SPF), the currently used in vivo International Standard method (ISO 24444:2019). As they are now recognised as ISO standard methods, products can be SPF without involving human volunteers.
Regulatory Requirements for SPF
Nowadays, sunscreen testing varies globally due to differing regulations aimed at ensuring product safety and efficacy:
- European Union (EU): Sunscreens must pass both, SPF and UVA tests, including in vivo and in vitro assessments based on ISO standards. Products meeting the criteria test must display the SPF value and UVA circle logo.
- United Kingdom (UK): Retains EU Cosmetic Regulation post-Brexit, requiring dual compliance with UK-specific and EU standards through the OPSS (Office for Product Safety and Standards), ensuring accurate SPF and UVA protection.
- United States (US FDA): Requires “broad-spectrum” labelling for products that protect against both UVA and UVB rays. Proposed updates aim to enforce higher SPF values and improved UVA coverage.
- Asia-Pacific (APAC): Utilizes the PA system to rate UVA protection levels from PA+ to PA++++, with testing protocols that meet both local and international standards.
Why Compliance Matters in the Cosmetics Industry
Testing sunscreens is essential not just for legal compliance but also for consumer safety. Reliable and thoroughly tested products ensure protection against harmful UVA and UVB rays.
Adapting laboratory testing to new methods will naturally diversify their procedures and align protocols with more ethical standards, avoiding both, animal and human volunteers testing.
Partnering with regulatory experts like Cosmeservice ensures compliance, protects your brand, and maintains customer trust. Learn more about our testing services or contact us.
References
- Regulation (EC) No 1223/2009 of the European Parliament and of The Council of 30 November 2009
- Amendment of Article 14 (14) of Schedule 34 of the Product Safety and Metrology Statutory Instrument (UK)
- Federal Food, Drug, and Cosmetic Act (FD&C Act)
- Diffey, B.L. (2002). “What is SPF?” Photodermatology, Photoimmunology & Photomedicine.
- Stanfield, J.W. (2018). “Understanding Sunscreen Testing and Efficacy.” Journal of Cosmetic Dermatology.
- Commission Recommendation of 22 September 2006 on the efficacy of sunscreen products and the claims made relating thereto
- ISO 23675:2024 – In vitro determination of sun protection factor (SPF)
- ISO 23698:2024 – Measurement of the sunscreen efficacy by diffuse reflectance spectroscopy
