Patch Tests & Regulatory Compliance with CuTest

In our Educational Fridays Newsletter, we interviewed Stewart Long FRSC , an expert in Patch Tests and CEO of Cutest - The Skin Specialists .

Mr. Long shares his insights on cosmetic safety and patch testing, offering valuable knowledge in an easy-to-understand format.

Interested in patch test, and the cosmetic claims behind it, keep reading :)

1- Are there different types of patch tests?

Yes, patch testing is a term used to describe studies that place products in exaggerated contact with skin to determine their irritation or allergenic potential. Products can be occluded, opened and applied for varying lengths of time, depending on the product and requirements.

2- How to choose the correct patch test method for a product?

There is no single patch test protocol and it is important to choose the most appropriate for your products. For example, products with surfactants are generally not suitable for HRIPT patch tests as they will cause irritation. These rinse-off products need to be tested in a specific, appropriate type of test. Talk to an expert to ensure you run appropriate testing for your product. Be concerned if the testing company runs the same test for every product type.

Some patch tests are international standards (e.g. ISO10993) for topical medical devices, but most are generally agreed on principles and different clinics may offer differing protocols.

3- What is the best test for a hypoallergic claim?

A patch test cannot prove a product is hypoallergenic. The word of course means less allergenic: so the question is less than what? To make the claim, the current guidance is that you need to be confident all known allergens are eliminated from the formulation and you have some skin tolerability testing to support. Most clients ask us to run patch testing to show a product is suitable for sensitive skin, eczema-prone skin and to support dermatologically tested. The hypoallergenic claim is a combination of your product information and testing.

4- Is there any minimum requirement for the number of volunteers in a patch test?

You need a representative cohort of subjects for a valid patch test. Irritation reactions are generally infrequent, so with too few subjects, you are likely to miss reactions and underestimate problems in the market when thousands of products are sold. Sensitisation (allergenicity) patch testing needs large panels because only around 1:100 people are likely to have a sensitisation reaction. Sensitisation patch tests on small panel sizes are therefore not valid. For irritation patch tests, a panel size of 25 subjects or more will give reliable results and has been widely shown to be predictive. Panels of 10 or 15 subjects are not reliable.

5- Is a Cosmetic product safety assessment (CPSR) required before doing a patch test on human volunteers?

A CPSR of some sort should always be undertaken before exposing people to products in a patch test. A preliminary assessment should identify any potential ingredients of concern or aspects of the formulation that could cause harm to subjects. We have to consider the ethics of human testing and ensure we do not take inappropriate risks with testing. It is part of a responsible company's Corporate and Social Responsibility in the same way responsible sourcing is.

6- Is there any in vitro alternative for patch test?

In vitro irritation tests exist that are valuable screening tools before exposing people to products. They can give a good indication of potential irritation issues. In vitro tests cannot tell you if the product may sting, or cause redness, papules, broken skin or other problems. Only testing on people can give this important information that warns you about unexpected issues a formulation may cause when sold.

7- Is a patch test considered a gold safety standard for the USA market?

There is not a requirement by the FDA to run patch testing but for the U.S. market it is extremely common and many retailers expect testing to stock products.

8- Does passing a patch test as “non-irritant” mean a product is safe?

Generally, HRIPT tests are performed but be aware even these do not absolutely guarantee no reactions in the market. Similarly, ‘passing’ a patch test or showing low irritation potential does not guarantee any reactions in the market. If you sell enough products, someone will react, but you can be confident that issues are unlikely to be widespread if you have appropriate test data.

9- What is the best test for “ophthalmology tested” claims?

Ophthalmological testing requires the assessment of ocular irritation by a qualified expert, either an ophthalmologist or optometrist. They can assess the eye and eyelids for various signs of irritation and provide data that a product is unlikely to cause irritation if used around the eye. A separate study where dilute solutions of products, usually bath, hair and wash products are placed into the eye is also performed and assessed to ensure products that may splash in the eye are unlikely to sting or cause irritation. The claim of ‘no tears’ is often seen when this testing has been performed.

10- Requirements for “dermatologist approved” claim.

Dermatologist-tested or dermatologist-approved claims can be interchangeable in some people’s eyes. To use the dermatologist / dermatologically tested claim, a suitably controlled patch test and involvement or review by an experienced dermatologist are required. It can also be supported by other appropriate clinical testing that involves the dermatologist, so is not restricted to patch testing. Dermatologist-approved can be used interchangeably but does imply the dermatologist endorses the product, which can be trickier should you be challenged. What are they approving exactly? You need to discuss with experts how to use this claim to avoid challenges.

If you have any questions regarding the article. Feel free to write it in the comment section. We are more than happy to help you out. :)

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