Skin Barrier Strengthening Methods and Ceramide Cream?

In previous posts, I've been discussing the skin barrier and skin conditioning, focusing on atopic dermatitis. If you've been reading from the beginning, you'll understand that all these topics are interconnected.

Briefly speaking, there are various conditions that enable the skin to perform its functions well on its own. A wide array of elements are conditioned by coordinating with each other. Therefore, in the treatment of skin diseases, how to restore the skin's own conditioning becomes the core focus, and various intervention options that can help with this can be selectively utilized.

In some ways, it's just skin. One might even lightly dismiss this by simply saying that "Qi follows blood flow," and that improving peripheral blood circulation would allow the skin to function on its own. However, I hope that by looking a little more deeply into the detailed processes by which the skin barrier function is structured, we can gain various insights into the treatment of skin diseases.

Skin Barrier and Lipid

In this post, I will delve a bit deeper into the skin barrier in relation to lipids.

Structure of the Skin

This shows the skin progressively magnified. As you know, the skin consists of the epidermis and dermis, and the epidermis is further divided, from bottom to top, into the basal layer, spinous layer, granular layer, and stratum corneum. I've mentioned several times in previous posts that keratinocytes differentiate from the basal layer at the bottom, forming a unique "brick and mortar" structure that constitutes the stratum corneum.

The stratum corneum (SC) is a very important topic in skin barrier function. I believe that if you research various materials on the SC and study it in more detail, it will be helpful in your clinical practice.

Importance of the SC Layer

Anyway, if you continue to magnify and examine the SC layer, you'll find things filling the spaces between keratinocytes. It's lipid that acts like cement, sticking the keratinocytes together closely, like a brick wall.

This shows two representative lipids commonly found in the SC layer. One is free fatty acid (FFA). The other is sphingolipid, well-known by the name ceramide (CER). You've probably heard about ceramides in expensive cosmetics; that's where the story comes from.

Skin Type and Lipids

When discussing skin types, they are often classified as dry or oily. Strictly speaking, dry and oily aren't direct opposites. Dry skin refers to situations where the skin barrier is compromised, leading to a lack of intracellular Natural Moisturizing Factors (NMF) that can hold moisture, high Transepidermal Water Loss (TEWL), resulting in dryness and cracking. On the other hand, oily skin does not necessarily mean it's rich in moisture.

Source: Epidermal surface lipids

It is important to distinguish between two main types of oiliness present on the skin: (1) sebaceous gland-derived, and (2) SC-derived. These two categories differ. The lipid composition also shows differences. As mentioned earlier, lipids composing the SC are free fatty acids, ceramides, and cholesterol. Lipids secreted from sebaceous glands are, in order, triglycerides, wax esters, and squalene.

Moisturizers and the Skin Barrier

In the previous post on moisturizers, I mentioned that moisturizers can be classified as humectants, occlusives, and emollients. While a bit rough, if we use an analogy, humectants correspond to NMF, occlusives to sebum, and emollients to SC lipids. In other words, you can understand that moisturizers are formulated by mimicking the physiological effects of various components involved in the skin barrier and hydration.

SC Lipids and Atopic Dermatitis

So, what changes do these lipids undergo in patients with atopic dermatitis? This shows a comparison of the proportions of various ceramide subclasses in healthy individuals versus atopic dermatitis patients. A difference in the compositional ratio of ceramides is immediately apparent. This means there are differences in the types and compositional ratios of ceramides that constitute SC lipids between healthy individuals and atopic dermatitis patients.

This compositional difference is likely related to the vulnerability of the skin barrier's physical structure. It can be seen that not only ceramides but also SC lipids in various forms are inappropriately produced and secreted in atopic patients. This phenomenon is called lipid abnormality. If you search with this keyword, you should be able to find relevant materials.

Elias, P. M. (2014). Lipid abnormalities and lipid-based repair strategies in atopic dermatitis. Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 1841(3), 323–330. doi:10.1016/j.bbalip.2013.10.001

Anyway, ceramide. This is the context in which cosmetic companies emphasize ceramides. So, if you use cosmetics containing ceramides, will your skin barrier be restored? I haven't found research on this, but it's likely not that simple. The reason is that it's not the chemical action of the ceramide component that is important, but rather the physical structure formed by SC lipids, including ceramides, arranged together in the SC, that plays a role.

Therefore, it's not about merely pushing ingredients from the outside, whether through cosmetics or ointments. I believe our job is to consider ways to encourage the skin's own functions to work smoothly and enable it to construct its barrier independently.

Summary

1. The "ceramide, ceramide" emphasized in cosmetic advertisements refers to this ceramide, which is a major issue in SC lipids.
2. Let's consider various approaches to restoring the skin barrier.

Thank you for reading.