We all need moisturizers in our skincare routine, no matter what our skin type or skin concerns. But what are the different types of moisturizers, and which one do you need in your routine?
The knowledge of different types of moisturizers will help you to discern which type of moisturizer is best for your skin type and concerns. The use of moisturizer varies according to the specific function it performs e.g., reducing water loss or attracting and binding water to the skin.
Skin barrier
Let’s talk a little bit about the skin and its barrier to understand what are the three different types of moisturizers and why do we need them?
Our skin is the largest organ of our body and has three layers; epidermis, dermis and hypodermis, all three of which vary significantly in their anatomy and function.
For the sake of this blog post, we are concerned with just the epidermis. The outermost layer of epidermis is called the stratum corneum (SC) and it is this structure of SC that is imperative for overall moisturization. With this in mind, let’s understand the formation and functionality of the SC, which involves 3 key aspects.
Corneocytes and lipid matrix
SC is made up of dead keratinocytes, also referred to as corneocytes. These cells have a protein envelope and are embedded in a lipid matrix constituted by ceramides, cholesterol and free fatty acids.
Think of it as the brick-and-mortar structure. So, essentially protein bricks embedded in a lipid mortar.
These layers of corneocytes provide the stratum corneum its barrier function, all physical, chemical and immunological barriers. The lipid matrix acts as a moisture barrier and is also a means of entry for most topical products.
Desquamation
These corneocytes shed regularly by the process of desquamation. From the lowest layer of epidermis, known as the stratum basale, keratinocytes undergo cell division and move towards the skin surface. These keratinocytes pass through multiple stages of differentiation to finally become corneocytes when they reach the skin’s surface. Further, this process typically takes 2–4 weeks and is absolutely critical for maintaining the skin homeostasis.
Natural moisturizing factors
In addition to that, the SC contains molecules called the natural moisturizing factor (NMF). These include lactic acid, urea, amino acids and electrolytes. These molecules are important for hydration since they can absorb water from the atmosphere under certain conditions.
In addition, the formation of these molecules from the breakdown of a protein called filaggrin is dependent on external humidity conditions. When the water content is high, filaggrin is stable and NMF formation does not take place. Conversely, when the water content is low, filaggrin breaks down to produce NMFs which absorb water from the environment.
The stratum corneum of healthy skin has a water content between 10–30%. To maintain this, water from the deeper layers of the skin migrate upwards to hydrate the SC and is then lost to evaporation. This is called the Trans epidermal water loss (TEWL).
Furthermore, at water content <10%, corneocytes don’t remain pliable and crack, commonly referred to as dry skin. An intact skin barrier still allows a healthy range of TEWL, but a damaged skin barrier means an increase in TEWL. Therefore, an increased TEWL is a signal for the body to initiate barrier repair.
Moisturizers boost the water content of SC in a variety of ways. It either provides water to the SC from its water phase or protects against TEWL by forming a protective film on top of the skin or creates a smooth surface by filling the spaces between desquamated cells.
Goals of moisturization
Hydration
The first and foremost goal of moisturizing the skin is increasing the skin’s hydration. And so, this can be achieved by using ingredients that attract water to the skin’s surface and/or prevent TEWL by forming an impermeable layer that sits on top of the skin.
Improve smoothness and softness
The second important goal of moisturization is soft and smooth skin and this is essentially an assessment of corneocyte organization on the skin’s surface.
Infact, surfactants in the cleansers interact and solubilize some constituents of the intercellular lipids in which the corneocytes are embedded. What’s more, as these lipids are removed, the edges of corneocytes become rough. This can be remedied by using emollients which are oily substances that deposit themselves between desquamating corneocytes, creating a smooth skin feel.
Improve appearance
Lastly, some moisturizers increase skin radiance. In other words, this is the ability of the skin to reflect the light falling onto it, back into the observer’s eye, giving the skin a smooth finish.
Hence, moisturizers maintain the skin barrier, boost hydration and improve the overall appearance. It is clear that a variety of mechanisms are at play in order to achieve these goals. Let’s see.
Different types of moisturizers based on mechanism of action:
Humectants
Right now, the most popular out of the various types of moisturizers are humectants. Humectants are the compounds that attract water. They can draw water from the surrounding environment if the humidity is >70%. In other cases, they usually draw water from the deeper layers of the skin, although over time this can exacerbate dryness in some cases.
Common humectants:
- Honey
- Glycerin
- Alpha-hydroxy acids or AHAs including glycolic acid and lactic acids. Most of us know their function as a chemical exfoliant however, they also improve the barrier function by increasing levels of ceramides.
- Urea
- Propylene glycol
- Sorbitol
- Hyaluronic acid
- Sodium pyrrolidine carboxylic acid (PCA)
- Panthenol
Occlusives
Occlusives sit on top of the skin and form a barrier to prevent or reduce TEWL. Ultimately it allows the water content of stratum corneum to be replenished from the deeper layers of the epidermis as well as dermis. The most effective occlusive is petrolatum, in any case it prevents nearly 99% water loss through the epidermis. This is my favorite among the various types of moisturizers.
Common occlusives:
- Hydrocarbons: Petrolatum, mineral oil, paraffin, squalene
- Silicones: Dimethicone, cyclomethicone
- Animal and vegetable fats: Shea butter, grape seed oil, avocado oil, hemp oil, jojoba oil, sesame seed oil
- Fatty acids: Lanolin acid, stearic acid
- Fatty alcohols: Lanolin alcohol, cetyl alcohol
- Polyhydric alcohols: Propylene glycol, butylene glycol
- Wax esters: Lanolin, beeswax
- Sterols: Cholesterol
- Phospholipids: Lecithin
- Vegetable waxes: Candelilla, carnauba
Emollients
Emollients are oily substances that condition the skin and improve its appearance and smoothness. In particular, they fill in the spaces between the desquamating corneocytes. Furthermore, emollients do not necessarily moisturize the skin
Common emollients:
- Dry emollients: Isopropyl palmitate, isostearyl alcohol
- Fatty emollients: Propylene glycol, jojoba oil, castor oil
- Astringent emollients: Dimethicone, cyclomethicone
- Protective emollients: Isopropyl isostearate
Humectants: attract water into the skin
Occlusives: form a layer on top of the skin to prevent water loss
Emollients: condition the skin to give a smooth and soft feel
On the whole, most moisturizers in the market have a blend of these categories to effectively deliver hydration into the skin. A combination of these ingredients will determine if the moisturizer/product is beneficial for a certain skin type. Furthermore, these ingredients can be amalgamated into various formulations, including lotions, creams, serums or ointments that establish their usage in a particular kind of environment like winters, hot and humid summers etc.
Moisturizers undoubtedly constitute an essential part of our skincare armamentarium, and we must make the best use of them. Now that you have your guide to different types of moisturizers, let me know in the comments what is your skin type and your holy grail moisturizer! Don’t know your skin type, find out here.
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