Introduction to the skin
Skin: What it is and how it works
One of the main reasons why it’s taken me more time than originally planned to bring a product to market (besides the fact that we need time for the botanical ingredients to grow from seed) is because much of my training as a formulator is focused around the science of the skin. And the skin is waaaaay more intricate than one might think! If people in general (and some brands…) knew more about the skin, then they might be better informed as to which products not only actually work, but also work specifically for themselves. Because it can be intricate, confusing, and somewhat science-y, I thought I would put together a simplified introduction to the skin so that it might prove useful to get to know your own a little better. 😉
While countless papers, studies, and books have been written on this subject, I will focus on the basics of two topics that are, in my opinion, the most pertinent when it comes to skincare: what the skin is comprised of, and how stuff (cosmetic ingredients) penetrates the skin.
WHAT IS THE SKIN?
The skin is comprised of 3 main segmented regions: the epidermis (outer), the dermis (middle), and the hypodermis (lower). The epidermis receives a lot of, if not most of, the attention of skincare enthusiasts and experts alike because it is where most of the work of a product shows its results. The dermis is the main part of the skin, where a number of elements cohabitate: hair follicles, lymph vessels, capillaries, sweat and sebaceous glands, nerve endings, and fibroblasts (the collagen-making cells). And, lastly, the hypodermis, which is primarily a layer of fat that provides a padding to prevent injury to your underlying muscles.
The epidermis, the layer of skin you can actually see, has 4 to 5 separate sub-layers depending the part of the body that you're looking at (the tougher parts of the body, like the soles of your feet, have that additional 5th layer), but the layer that people focus on when it comes to the look and feel of the skin is the stratum corneum, the outermost layer of the epidermis. Skin cells are created deeper down in the middle section of the skin, the dermis, and over the course of about 30 days they move up to the stratum corneum, changing their composition as they move up and age. Once they reach the stratum corneum, they are towards the end of their lifecycle and have become flattened and drier and thereby create a shell that then protects us from external harms (nature’s elements, bacteria, UV radiation, environmental pollution, etc.). Before they dry completely, and subsequently get sloughed off as dead skin, they still contain some water. In healthy skin, the stratum corneum consists of about 30% water.
The most common analogy you’ll hear about the composition of the stratum corneum is that of a brick and mortar shell. The skin cells are the bricks and the mortar is composed of what is called the intercellular lipids (ie. oils/fats). These lipids are primarily made of ceramides, cholesterol, and free fatty acids, and when the skin is healthy it usually means these lipids are at their optimal ratio (which is more or less the same for everybody). When people refer to the “Skin Barrier Function”, they are basically talking about how good your stratum corneum is at protecting the body from the external environment and preventing water loss (what’s called Transepidermal Water Loss). The Lipid Barrier within this equilibrium plays a crucial role in regulating and maintaining proper skin function. These lipids tend to decrease as we age leading to an overall feeling of dryness, which is why restoring them with a good facial serum is incredibly important to keeping the skin balanced, soft, and beautiful.
Still with me? 🤓 I know this can all be a bit dense, particularly at first, and there are still a bunch of aspects of the skin that I’m leaving out for simplicity's sake. However, as a basic take-away, when looking for effective skincare and healthy skin, it is important to know that a good balance of lipids is crucial (along with a diverse skin microbiome, but that’s a whole other subject). If your lipid ratios are out of whack, it is likely that your skin will manifest this lack of harmony through, for example, dryness, irritation, or acne, especially if you are prone to any of those conditions.
HOW DOES STUFF PENETRATE THE SKIN?
Now that we know the basics of the stratum corneum (i.e. outermost layer of the epidermis, i.e. the Skin Barrier, i.e. the Brick Wall), we can get into the basics of how a skin product like a serum or a cream, penetrates this barrier and helps us to harmonize, repair, strengthen, and therefore maintain healthy skin. There are two main elements that carry beneficial chemical compounds into the skin: water and oil. This is why the majority of the products on the market are either water-based, oil-based, or a combination of the two.
Let’s start with water-based products (and I’m gonna focus on “leave-in” products, “rinse-off” products are a separate conversation). And just to state the obvious: our skin doesn’t absorb water directly (osmosis). Otherwise our skin would balloon up every time we jumped into a pool! In fact, water tends to dry out our skin as it evaporates.
In any case, as you probably already know, water and oil don’t mix. Yet, there are different ways that you can combine the two, like in a cream where you use emulsifiers and heat to disperse one into the other and it looks like they mixed together into a single substance, but even then, at a molecular level, they do not fully mix. Again, this conversation can easily be doven into at greater depth with further intricacies and more science, but I will focus on the most basic aspects of how a water-based product enters the skin. Since the layer beneath the stratum corneum (the stratum granulosum) is essentially a waterproof sealant, water cannot penetrate beyond the skin’s outermost layer. Oils create a barrier to lock in moisture that is already in the skin, so when you use a water-based product like a cream or lotion it is the oil in the product that is protecting the moisture that is already there AND giving your skin a quick fix of surface moisture from the water. This then suggests that, while water is of course necessary in the skin, it is the oils in a product that are the real heros. 🙌
Oil-based products, on the other hand, can penetrate to deeper sections of the skin because of the fact that they are oil-soluble. They enter the skin primarily through the intercellular lipids (the mortar) and then depending on the size of the molecules of the constituents of the oil, penetrate in some cases down through the different layers of the epidermis. This provides a deeper level of nourishment and replenishment, and typically indicates a stronger long-term effect on the skin.
This is the main reason why I chose to pursue a facial serum as my first product. The formula I’ve designed is arranged to balance the ratio of epidermal lipids in the stratum corneum, as well as to provide phytonutrients that penetrate deeper into the skin, therein delivering a high-performance antioxidant product. The plethora of antioxidants in the formula prevent the natural production of free radicals, which means that they help in promoting and supporting the inherent properties of healthy skin. It is meant to make you feel good in your skin.
The first batch will be available in December, right on time for the holidays, so if you’re interested in giving it a try, provide your email below and you’ll receive a note from me when it’s ready!
xo,
Carolina
Sources:
https://www.ncbi.nlm.nih.gov/pubmed/12553851
https://www.ncbi.nlm.nih.gov/pubmed/12467638
https://www.ncbi.nlm.nih.gov/pubmed/16945325
https://www.ncbi.nlm.nih.gov/pubmed/26844894
https://www.ncbi.nlm.nih.gov/pubmed/24252189
https://www.ncbi.nlm.nih.gov/pubmed/8618046
https://www.ncbi.nlm.nih.gov/pubmed/9308554
https://www.ncbi.nlm.nih.gov/pubmed/1628964
https://www.ncbi.nlm.nih.gov/pubmed/27521253
https://www.ncbi.nlm.nih.gov/pubmed/20399614
https://www.ncbi.nlm.nih.gov/pubmed/29740318
https://www.ncbi.nlm.nih.gov/pubmed/18839043
https://www.ncbi.nlm.nih.gov/pubmed/1450595