In our last blog, one of the basics we covered was the layers of the skin. Do you remember the ‘mental note’? No stress if not, it was the ‘stratum corneum’ also known as ‘the horny layer’. The stratum corneum, or SC as we’ll refer to from here on in, is the outermost layer of the skin. Previously, this layer was considered to be a lifeless membrane that merely provided some mechanical protection from the outside world and prevented water loss from within. Over the last half a century or so, studies have emerged showing that in addition to the previous simplistic assessment of this layer, the SC has biological properties and functions that directly and substantially contribute to, not just skin health, but health in general. The main champion of this research was Professor Albert Kligman who can be credited with pioneering studies into the SC and founding, what is now known as, Corneobiology. His work was furthered by Dr. Peter Elias who established ten major functions of the SC, with Kligman adding a further six. We believe the following stratum corneum functions are worth noting as they have a considerable impact on skin health and appearance: Permeability – A healthy SC will allow for effective absorption and excretion. Absorption via the skin, although vital, can be a pro and a con. It can be extremely useful when applying quality products that can improve or maintain the SC, deeper skin layers, or health in general. However, it also allows for the absorption of harmful environmental chemicals including ones commonly found in mainstream skincare products, so be mindful of your environment, and what you apply to your skin. Antimicrobial – A healthy SC will aid in protecting against bacteria and viruses. It does this via the acid mantle, being a slightly acidic layer (pH ranging from 4.5 to 6.2) of ceramides, free fatty acids and cholesterol. This acidic environment provides protection from microbes. If the SC’s homeostasis is compromised, so are its defenses, allowing microbes to invade affecting the skin and body’s health and appearance. Antioxidant – The SC regulates the production of antioxidants, in particular vitamin D, which protects against free radicals brought on by photo-oxidative stress, arguably the largest contributor to the signs of aging. Psychosensory – The SC provides feedback to the brain of its immediate surroundings. In order for the right messages to be transmitted, and the body to react appropriately, the SC must be healthy and working effectively. Hydration – The SC doesn’t just provide a mechanical barrier to water loss as previously thought. It is in fact permeable and regulates transepidermal water loss via the same layer that provides microbial protection. The hydrophobic properties of this ‘lipid layer’ (mental note for our next blog), can allow or prevent water loss, keeping the lower layers of the skin appropriately hydrated leaving skin moist and plump. Initiates inflammation – The SC can activate cytokines as a function of the immune system. Again, this can be a pro or a con. A proper functioning SC will trigger the immune system and cause inflammation as a defense mechanism when it senses a threat. However, a compromised SC can trigger inflammation at inappropriate times leading to troublesome skin conditions. Due to its diverse functions, the SC has attracted the attention of a number of scientific disciplines including molecular biologists, anatomists, physiologists, pharmacologists, geneticists and psychologists to name a few. This, in itself, vindicates the complex and vital role the SC plays in how the body functions, which is why ENIKŌ products focus on repairing and maintaining a healthy SC. Now that we have covered the basics of skin and in particular the SC, in future posts we will elaborate further on the stratum corneum, as well as lead into the importance of using appropriate products. We are starting to hear more and more about particular ingredients being harmful, so we will explain exactly why, and how to make sure your skin functions optimally and, in turn, have it looking as youthful and radiant as it should. Stay tuned! Sources and further information can be found at: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1468-2494.2011.00644.x https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3175800/