Three type of moisturisers explained: all you need to know

We all know how important is to moisturise the skin. I always say that if you can only buy three skincare products you should go for a cleanser, a moisturiser and sunscreen. However, do you know that not all moisturiser ingredients work in the same way? I’m sure you’ve heard about humectants, emollients and occlusive ingredients in skincare. They all contribute to keeping our skin moisturised but each one in a different way and at a different level. In this post, I am going to tell you the difference between the three type of moisturisers to help you choose the best one for your skin needs.

What is the structure of the skin barrier?

To understand the differences between these three ingredients we should be familiar with the skin barrier structure. The structure of the skin comprises three different layers: hypodermis, dermis and epidermis. The layer which keeps the skin hydrated is the most external one, the epidermis. In the epidermis, we can find the skin barrier, which protects us against microorganisms and external agents.

We can find different components in the skin barrier: keratinocytes, corneocytes, lipids, and the natural moisturising factor (NMF). All of them are important and contribute to keeping hydrated and healthy skin.

Keratinocytes/Corneocytes

The epidermis is made of 10-15 sheets of keratinocytes disposed over a lipid matrix. These keratinocytes are arranged in four different layers:

• Stratum Basale. The keratinocytes on the stratum basale cover the keratinocyte stem cells. Active cell proliferation and division take place in this layer.
• Stratum Spinosum. This layer comprises 8-10 sheets of keratinocytes with reduced potential for cell division.
• Stratum Granulosum. This layer consists of 3-5 sheets of keratinocytes that cannot be divided.
• Stratum Corneum. This is a cornified layer of the skin consisting of 15-30 sheets of corneocytes.

Keratinocytes move from the stratum basale to the stratum corneum. During this trip, they lose the nucleus and other cell organelles producing corneocytes. Corneocytes are, therefore, dead cells. The stratum corneum is biologically dead but biochemically active, as lots of biochemical reactions take place in this layer.

We can say that the skin is a wall and the corneocytes are the bricks forming the wall.

Lipids

The skin needs something to bring these bricks or corneocytes together. This is the function of lipids. Lipids act as cement keeping corneocytes together.

There are different types of lipids between the corneocytes. The lipid composition is 50% ceramides, 25% cholesterol, 15% free fatty acids, and 10% cholesterol esters.

This lipid matrix combines with the environmental water and with the sweat to produce an emulsion which avoids internal water loss.

Natural Moisturising Factor (NMF)

This is another important component of the epidermis. Among the NMF we can find amino acids (40%), pyrrolic carboxylic acid (12%), lactic acid salts (12%), urea (7%), inorganic salts (18.5%) and small amounts of other components like ammonia, creatine, uric acid, citric acid salts, sugars and peptides. The natural moisturising factor is 15-20% of the stratum corneum.

The natural moisturising factor is important for the appropriate stratum corneum hydration, desquamation and plasticity.

Now that we know the skin barrier structure, let’s see what each one of the moisturising ingredient types is.

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Three type of Moisturisers: Humectant

A humectant is a hygroscopic ingredient (with a capacity to absorb water) which attracts and retains water in the skin.

Any humectant ingredient attracts environmental water to the external skin layer. Then, they will help this water penetrates the skin and will retain it there. The skin will look plum and luminous.

Something very important to keep in mind about humectants is what makes them so useful, their capacity to attract water. That can also be inconvenient under certain circumstances. If we are in an environment with a high moist level the humectant will attract this water to our skin, which is something really good for skin health. However, we should be careful if we are in a dry environment. Under this condition, the humectant can attract water from the inner skin layers to the outside. That will dry our skin and, therefore, dehydrate it.

The main benefit of the humectants is that they keep the skin soft and moisturised all day avoiding, therefore, dry and dehydrated skin. They also help to eliminate dead cells.

Three type of Moisturisers: Emollients

The emollients are ingredients that can occupy the spaces between the corneocytes. They can trap and retain water. The skin will look smooth after applying an emollient.

Emollients are highly beneficial for people with very dry skin or with any skin concern, like psoriasis and eczema. However, people with healthy skin may avoid emollients.

Emollients nourish and moisturise the skin providing plasticity and leaving it soft. They help to soothe skin irritations (that is why they are very common for babies) and promote lipid production.

Three type of Moisturisers: Occlusive

An occlusive is an ingredient that does not penetrate the skin but forms a film or layers over it. This film avoids transepidermal water loss and helps to keep the skin hydrated. This layer helps to protect the skin against external factors like wind, cold, pollen, etc.

Normally occlusive ingredients are thick and heavy to avoid skin absorption. They are ideal for people with very dry skin, eczemas or psoriasis.

The layer an occlusive ingredient forms allow circulation of oxygen, nitrogen and other nutrients and, therefore, lets the skin “breathe”. This layer only avoids the circulation of water.

Differences between the three type of moisturisers

First of all, I would like to mention that one ingredient may have more than one function. I mean, an ingredient can be a humectant, emollient and occlusive at the same time. After mentioning that, the main difference between them comes from the layer where they act, from how deep they penetrate the skin.

Humectants work on the deeper epidermis layers. They attract and retain water there, keeping the skin hydrated. Everybody should include a humectant in the skincare routine, independent of which skin type.

Emollients also get absorbed by the skin but only at the most external level. They are indicated for people with any skin concern, but not for people with healthy skin.

Finally, occlusive ingredients are not absorbed and stay on the skin surface, creating a protective layer. They are good for people with any skin type. However, people with acne-prone skin may look for non-comedogenic occlusive ingredients.

I hope I helped you to understand the difference between these three types of ingredients. You can now choose a good humectant and maybe any other, depending on your skin type and concerns.