In a crowded personal care marketplace promoting the smallest benefit or point-of-difference can help guide the consumer to place your product in their shopping basket. In this week’s blog we talk about a skin irritation test method to identify the subtlest differences in ingredient and product mildness, benchmarking your products and how to get the data to substantiate your on-pack claims.
Why is mildness ‘a thing’?
Cosmetic and personal care ingredients by the very nature of how and where they are used – on our skin – must be milder than chemicals used in most other industries. Human skin is truly amazing. Around 2 square metres of this waterproof yet ‘breathable’, self-healing material acts as the first level of defence for our immune system. It plays home to its own family of micro-organisms, our microbiome, and it tolerates a range of assaults in daily life (think tanning, tattoos, make-up, piercings, cuts and scrapes). But it has its limits. Factors such as air pollution, air conditioning, extreme weather, poor diet, frequent washing and sanitising, chemical exposure (eg household products), hormonal changes, age, ethnicity, underlying skin diseases and stress can all make our skin more prone to adverse reactions.
How mild is mild?
Given the prevalence of these ‘stress’ factors in our daily lives it seems logical that consumers seek out the products that will help protect the skin’s barrier function and not aggravate or irritate. And a quick scan of the shelves in any health and beauty store shows that the cosmetics and toiletries industry has responded; more and more leave-on and rinse-off products claiming mildness or formulated for sensitive skin. To stay ahead, manufacturers need to be able to back up claims that products are mild and even ‘out-mild’ the competition. But how? The current trend requires innovative natural and synthetic ingredients along with new formulation techniques which enhance mildness and can even reverse adverse reactions such as Irritant Contact Dermatitis (ICD). To prove how a product or ingredient works and support these claims, we need increasingly sensitive methods to assess the irritation potential of these milder ingredients and formulations.
Current Test Methods
There are established in vitro skin irritation test methods. For example, OECD Test Guideline 439 – an internationally approved regulatory method used for hazard identification in various sectors of the chemical industry as well as for cosmetic ingredients. One drawback of this method is that it was designed to detect the irritation potential of relatively irritating chemicals, and the Test Guideline states that it can’t be used to differentiate mild irritants (GHS category 3) from standard ones (GHS Class 2). Essentially it only gives us a “yes/no” answer.
A variation of this test, known as the ET50 method*, provides more than just the basic answer to the question “is it irritating or not?”, and allows more detailed classification as a Severe, Moderate, Mild or Minimal / Non-Irritant. It can be used to assess relative mildness and the ET50 values can be used to place a range of candidate ingredients or products into a rank order of irritation potential. It also allows comparison with a database of ET50 values covering different product types, as well as direct correlation against specific benchmark products. For example, you might choose to compare previous formulations in your own range, or with competing / leading brands, to ensure that industry standards for skin mildness are being matched or even improved.
Beyond Mild – XtraMild
Typically, the ET50 skin irritation test method collects results up to an 18 hour endpoint, at which time there may be no distinguishable differences observed. For some of the mildest components and products in development and on the market, continuing the study out to 24 and 48 hours helps to tease out the differences in very mild systems. In turn these results help formulators benchmark their creations and allow marketers to make credible, science-backed claims of mildness. XCellR8 pioneered this development and we call it XtraMild.
*The ET50 is the time taken to reduce the health of the cells by 50% compared with untreated skin models.