How Sun Protection Factor is Measured and Verified

Determining a sunscreen’s Sun Protection Factor (SPF) is essential to assess its effectiveness in shielding the skin from harmful ultraviolet (UV) radiation. SPF quantifies the level of protection against UVB rays, which are primarily responsible for sunburn and can contribute to skin cancer. Accurate determination of SPF involves both in vivo (on human subjects) and in vitro (laboratory-based) testing methods.

HOW DO YOU KNOW YOUR SPF IS ENOUGH?

In Vivo Testing

The traditional method for determining SPF is the in vivo test, as outlined in ISO 24444:2019. This procedure involves applying the sunscreen to the skin of human volunteers and measuring the time it takes for erythema (redness) to develop compared to unprotected skin. The SPF value is calculated by dividing the amount of UV exposure that causes erythema on protected skin by the amount that causes erythema on unprotected skin. While this method has been the standard, it raises ethical concerns due to the intentional exposure of participants to potentially harmful UV radiation.

In Vitro Testing

To address these concerns, in vitro methods have been developed. These laboratory-based techniques measure the sunscreen’s ability to absorb or reflect UV radiation without involving human subjects. One such method is specified in ISO 23675:2024, which provides guidelines for determining SPF by analyzing the spectral absorbance characteristics of sunscreen products. This approach is applicable to various formulations, including emulsions and alcoholic solutions, but excludes powders and sticks.

Recent Developments

In early 2025, the International Organization for Standardization (ISO) approved two new SPF testing methods aimed at providing more ethical and less invasive alternatives to traditional in vivo tests. These methods seek to deliver reliable evaluations of UV protection while minimizing risks to human participants. The adoption of these new standards marks a significant advancement in sunscreen testing, promoting both accuracy and ethical responsibility.

Expected SPF Based on Sunscreen Agents

While in vitro and in vivo testing are necessary for precise SPF determination, formulators often estimate the expected SPF based on the type and concentration of active sunscreen agents used. For instance:

• Avobenzone: Provides UVA1 protection. Allowed use levels vary by region (e.g., USA 3%, EU 5%). Does not significantly increase SPF on its own.
• Homosalate: Offers UVB protection. Allowed up to 15% in the USA. Specific SPF contribution data may not be available.
• Octocrylene: Protects against UVB. Usage levels differ depending on combination with other sunscreens.
• Octyl Methoxycinnamate (OM-Cinnamate): Provides UVB protection. In the USA, allowed up to 7.5%. Approximately 1% concentration yields an SPF of about 1.5.
• Oxybenzone: Offers protection against UVB and UVA2. Allowed up to 6% in the USA. Approximately 1% concentration yields an SPF of about 1.5.

It’s important to note that these figures are approximate, and the actual SPF of a final product can only be accurately determined through standardized testing methods.

See the last chart here by https://www.makingcosmetics.com/

Sunscreen	UV Protection*	Allowed Use Level	Expected SPF Increase
Avobenzone	UVA1	USA 3%, EU 5%, Brazil 5%, Japan 10%, Australia 5%	None
Homosalate	UVB	USA 15%, EU 10%, Japan, 10% Australia 15%	No data available
Octocrylene	UVB	USA 10% if used alone and 7-10% if used with other sunscreens	No data available
OM-Cinnamate	UVB	USA 7.5 %, EU 10%, Japan 20 %, Australia 10%	1% gives a SPF of about 1.5
Oxybenzone	UVB, UVA2	USA 6 %, EU 10%, Japan 5%, Australia 10%	1% gives a SPF of about 1.5
Titanium Dioxide	UVB, UVA2	USA 25%, Japan no limit	1% gives a SPF of about 1.3
Titanium Dioxide (micronized)	UVB, UVA2		1% gives a SPF of about 2.5
Zinc Oxide	UVB, UVA2, UVA1	USA 25%, EU 25%, Japan no limit, Australia 20%	1% gives a SPF of about 1
Zinc Oxide (micronized)	UVB, UVA2, UVA1		1% gives a SPF of about 1.5
Zinc Oxide (micronized & coated)	UVB, UVA2, UVA1		1% gives a SPF of about 1.5
Zinc Oxide (micronized) plus Titanium Dioxide	UVB, UVA2, UVA1		5% each gives a SPF of about 12-19
OM-Cinnamate plus Titanium Dioxide (micronized)			5% each gives a SPF of about 12-19
OM-Cinnamate plus Octyl-Salicylate			5% each gives a SPF of about 10-18

*UVA1 = 340-400 nm, UVA2 = 320-340 nm, UVB = 290-320 nm

Zinc Repairing Facial Cream

Conclusion

Accurate SPF determination is crucial for ensuring the efficacy and safety of sunscreen products. While estimations based on active ingredients provide a preliminary understanding, standardized in vivo and in vitro testing methods are essential for precise measurement. The recent advancements in SPF testing methodologies reflect a commitment to ethical practices and scientific accuracy in the cosmetic industry.

NOTE: SPF testing must be done by special laboratories that have a lot of expertise and experience. Here are laboratories that offer this service:

• Suncare Research Laboratories
• AMA Labs
• CPT Labs

SOURCES:

Typology Paris

Sun Protection: Two New SPF Testing Methods Approved by ISO.

February 11, 2025 — The ISO approved two new SPF methods at the beginning of 2025. What are they and how will they impact sun care? Discover the details here.

gafchromic.com

[PDF] A new in-vitro method for determination of Sun Protection Factor

October 30, 2016 — A new in-vitro SPF test method for determining the efficacy of sun care products was proposed and evaluated. The test method is based on UV …

 

ISO

ISO 23675:2024 – Cosmetics — Sun protection test methods

December 18, 2024 — This document specifies a method for the in vitro determination of sun protection factor (SPF). This method is applicable to sunscreen products.

MakingCosmetics

How a SPF is Determined – Making Cosmetics

The SPF can only be determined accurately by in-vitro and/or in-vivo testing. Sunscreen, UV Protection*, Allowed Use Level, Expected …

Cosmetics & Toiletries

Good As Gold: Validating Alternative SPF Test Methods

April 2, 2020 — In silico SPF determination methods are becoming increasingly popular; they often provide realistic, usually rather conservative results. In …

Typology Paris ; Sun Protection: Two New SPF Testing Methods Approved by ISO.

February 11, 2025 — The ISO approved two new SPF methods at the beginning of 2025. What are they and how will they impact sun care? Discover the details here.

jasco-global.com

Analysis of Sunscreen SPF/PA Using a Spectroscopic Measurement …

February 1, 2021 — The system is used to calculate the SPF and the PA values from the transmittance spectra of sunscreens using a UV-visible spectrophotometer.

Cosmetics & Toiletries

Good As Gold: Validating Alternative SPF Test Methods

April 2, 2020 — In silico SPF determination methods are becoming increasingly popular; they often provide realistic, usually rather conservative results. In …

gafchromic.com

[PDF] A new in-vitro method for determination of Sun Protection Factor

October 30, 2016 — A new in-vitro SPF test method for determining the efficacy of sun care products was proposed and evaluated. The test method is based on UV …

MakingCosmetics

How a SPF is Determined – Making Cosmetics

The SPF can only be determined accurately by in-vitro and/or in-vivo testing. Sunscreen, UV Protection*, Allowed Use Level, Expected …

ISO

ISO 23675:2024 – Cosmetics — Sun protection test methods

This document specifies a method for the in vitro determination of sun protection factor (SPF). This method is applicable to sunscreen products.

SciELO

[PDF] Determination of sun protection factor (SPF) of sunscreens … – SciELO

The proposed UV spectrophotometric method is simple, rapid, employs low cost reagents and can be used in the in vitro determination of SPF values in many …

Regulations.gov

[PDF] INTERNATIONAL SUN PROTECTION FACTOR (SPF) TEST METHOD

The sun protection factor for the product (SPF) is the arithmetic mean of all valid SPFi results from each and every subject in the test and should be …

ScienceDirect

Sunscreen testing: A critical perspective and future roadmap

In silico methods use computational simulation approaches to estimate the SPF value by

 

 

In recent weeks, (again) several popular acne treatment products have been voluntarily recalled due to concerns over benzene contamination, a known carcinogen. Thanks to this headline Report:

The U.S. Food and Drug Administration (FDA) conducted tests on 95 acne products containing benzoyl peroxide and found elevated benzene levels in six of them, leading to these recalls.

The affected products include: La Roche-Posay Effaclar, A couple of Walgreens Acne Brands, and Proactiv, SLMD brands. (detailed lists can be found all over the internet this week).

This article takes a deeper dive into these reports and the FDA actual findings.

Due to the new media storm, Brands such as La Roche-Posay, Proactiv, and Walgreens have taken precautionary measures to remove specific products from retail shelves.

The FDA’s own site confirmed that most skincare products contain extremely low levels of benzene, well within safe limits—especially when used before the expiration date. This means that properly tested products from reputable brands are safe for daily use. They also concluded that some of these elevated levels may only be found in products that are near expiration dates.

WHAT IS BENZENE?
Benzene is a colorless or light-yellow, flammable, sweet-smelling liquid chemical compound often associated with industrial use, but lately it is getting more attention for being found in trace amounts in some skincare products.

It’s a hydrocarbon made up of six carbon atoms in a hexagonal ring, each bonded to a hydrogen atom. Benzene’s unique electron distribution gives it remarkable stability, making it less likely to react chemically. It’s used in the chemical and pharmaceutical industries as a solvent and starting material for many chemicals, including plastics, resins, rubber. It’s primarily a byproduct of certain chemical reactions and is sometimes used in product formulations as a solvent or preservative. However, it is NOT an intentional ingredient in quality skincare.

 FDA Findings on Benzene in Skincare

 Benzene Goes by Many Names!
While benzene itself is rarely listed on ingredient labels, it can sometimes appear under different names, including:
✔️ Benzol
✔️ Phenyl hydride
✔️ Coal tar naphtha

More Details on BENZENE: https://www.britannica.com/science/benzene

“Benzene is a colourless liquid with a characteristic odour and is primarily used in the production of polystyrene. It is highly toxic and is a known carcinogen; exposure to it may cause leukemia. As a result, there are strict controls on benzene emissions.”

Assuming most skincare product manufacturers and chemists understand the nature of Benzene, it stands to reason that they would NEVER knowingly formulate skincare products with this dangerous carcinogen.

 According to the CDC Chemical Fact-Sheet:

https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/benzene.html

Benzene is a colorless or light-yellow liquid at room temperature, characterized by a sweet odor and high flammability. It evaporates rapidly into the air, is heavier than air—allowing it to settle in low-lying areas—and exhibits limited solubility in water, tending to float on the surface.

Sources of Benzene Exposure

Benzene occurs both naturally and through human activities. Natural sources include volcanic eruptions and forest fires. It is also a component of crude oil, gasoline, and cigarette smoke. Industrially, benzene ranks among the top 20 chemicals produced by volume in the United States, serving as a precursor in the manufacture of:

• Plastics
• Resins
• Nylon and synthetic fibers
• Detergents
• Drugs
• Dyes
• Lubricants
• Pesticides
• Rubbers

Common environmental sources of benzene exposure include tobacco smoke, gasoline stations, motor vehicle exhaust, and industrial emissions. Indoor air may contain higher benzene levels due to products like glues, paints, furniture wax, and detergents.

It stands to reason that one may sooner be affected by Benzene exposure if they smoke cigarettes or breathe in motor vehicle exhaust, than putting acne cream on their face.

Health Effects of Benzene

Benzene disrupts cellular function, particularly affecting bone marrow’s ability to produce red blood cells, leading to anemia. It can also compromise the immune system by altering antibody levels and reducing white blood cell counts. Acute inhalation of benzene may result in drowsiness, dizziness, rapid or irregular heartbeat, headaches, tremors, confusion, unconsciousness, and, at extremely high levels, death. Ingestion can cause vomiting, stomach irritation, dizziness, sleepiness, convulsions, rapid or irregular heartbeat, and potentially death. Direct contact with benzene can irritate the skin, eyes, and respiratory tract.

DON’T BELIEVE ALL THE HYPE AND DO YOUR OWN RESEARCH

Skincare creator, influencer and educated product researcher, Charlotte Parlermino is doing much to help DEBUNK rampant media attacks on products and identify fear-based messaging as it pertains to skincare products and what consumers should actually be worried about.

https://www.tiktok.com/@charlotteparler/video/7481300648756104478

“Let us be free from the NON SCANDAL of #benzene and #larocheposay , hope the social media team is ok.  Nothing bugs me more than getting mad about the right issues (carcinogens) but wasting time with these stories that don’t tell the whole story riling us up about NOTHING. Freak out about the dismantling of the EPA or something”

It’s important to note that these recalls are at the retail level, meaning products are being voluntarily removed from store shelves BY THEIR MANUFACTURERS and online marketplaces in light of the media scares and to prevent further issues.

The FDA has stated that even with daily use of these products for decades, the risk of developing cancer due to benzene exposure is very low. Consumers are advised to check for expired products and dispose of them accordingly.

Limited number of voluntary recalls initiated after FDA testing of acne products for benzene; findings show a small number of products with elevated levels of benzene contamination

https://www.fda.gov/drugs/drug-safety-and-availability/limited-number-voluntary-recalls-initiated-after-fda-testing-acne-products-benzene-findings-show

“… 95 acne products containing benzoyl peroxide for possible benzene contamination. FDA has concluded that a limited … products had undetectable or extremely low levels of benzene. FDA initiated independent testing following receipt … the agency that raised concerns about elevated levels of benzene in certain acne products containing benzoyl peroxide. …”

STAY AWARE AND STAY INFORMED

In light of these events, brands like Vivoderm Natural Skincare emphasize their commitment to 100% natural, toxin-free formulations. Vivoderm assures consumers that their products do not contain benzene, aligning with their dedication to providing safe and nourishing skincare solutions.

This situation underscores the importance of fact-checking and thorough research when selecting skincare products. Consumers are encouraged to:

• Review Ingredient Lists: Understand the components of products and their potential effects.
• Stay Informed: Keep abreast of product recalls and safety alerts issued by reputable organizations like the FDA or the CDC,  NOT just rely on media outlets and sensationalized reporting.
• Choose Transparent Brands: Always Opt for companies that prioritize transparency and consumer safety in their formulations.

By making informed choices, consumers can better protect their health and ensure the efficacy of the skincare products they use.

 

MEDIA HYPE SOURCES:

https://people.com/carcinogen-found-in-acne-products-prompting-recall-11697357

https://www.southernliving.com/l-oreal-la-roche-posay-effaclar-duo-acne-treatment-recall-11694889

https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/benzene.html