In this week’s blog we are taking a look at why mildness testing is so important, and how the super-sensitive XtraMild testing method can be used to test a wide variety of products, including surfactants, wash-off formulations, leave-on products, and baby care ranges.
Let’s focus on why there’s a need for new tests to predict mildness
There are many contributing factors to the increased incidences of skin reactions, but stress comes out on top with the World Health Organisation (WHO) describing it as the “health epidemic of the 21st century”. This is because stress puts our inflammatory reactions on alert and lowers the threshold to elicit a reaction. Other factors include air pollution, chemical exposure, frequent washing, hormonal changes, and poor diet, to name a few.
Around 37%* of consumers actively avoid certain skincare products as they are worried about a skin reaction. This highlights the demand from consumers for ever milder products, that they feel confident using even when their skin feels extra sensitive.
* Naldi et al (2014). Prevalence of self-reported skin complaints and avoidance of common daily life consumer products in selected European regions. JAMA Dermatol 150(2): 154-162
How do we intend to start predicting mildness for certain products?
It’s been well established that tissue viability has historically been used as a model of skin irritation. We use 3D human skin models, grown commercially in a lab, taken from human cells. These are an excellent model of human tissue with all the representative layers you’d expect to see in human tissue. The test items (a chemical ingredient or a finished formulation) can then be applied directly to the tissue surface – this gives us a good model of “real life” exposure. There are no solubility limitations for this test – we can apply a test item or formulation as we might do in real life.
In this test we take the tissue models and apply the test item for various time points (1, 5, 18, 24 and 48 hours). Some traditional tests for irritation only look at the result at a single time point whereas we want to see the effect a substance has over time. This will help us really tease out the differences between really mild items and the difference in viability that we see. The percentage of viability at each time point will determine the ET50 value which we can then use to place the test item into a category of irritation. We can also compare those values to find out not only the category but how two products compare, and which comes out milder.
What about baby care?
Mildness is particularly important when it comes to baby care. From safety drivers like maintaining pH balance of the skin, avoiding irritation to the skin and eyes, and ensuring microbiome integrity, to commercial drivers such as comparative information between multiple candidate formulations, mildness is key when it comes to developing baby care products.
Mildness testing in other tissues: Eye mildness test
For our mildness to eye test, we use a human reconstructed cornea. This model has a really good simulation of the human cornea. The key difference between the eye and skin models is the eye doesn’t have the barrier the same as the skin – this makes it more vulnerable to irritating products. We use an ET50 type method, like XtraMild to skin. This test can be particularly important to package together with the skin test for any products that are going to come close to the eye: mascara, shower gel, shampoo etc.
Want to find out more about our mildness testing? Get in touch today.