Understanding skin layers to better target your skincare.
Understanding the different layers of the skin allows you to make better skincare choices. Not all products act at the same level. In a well-constructed routine, the goal is to act at the right level, with the right texture and the right active.
The skin is composed of three main layers: the epidermis, the dermis, and the hypodermis. Each has sub-layers and specific functions. To achieve balanced, durably hydrated skin, it is important to act at different levels.
The epidermis: the first protective barrier
The epidermis is the most superficial layer of the skin. It is what we see and touch. Its main role is to protect against external aggressors and limit water loss. This layer is composed of several sub-layers that work together to maintain skin balance.
The stratum corneum: the skin's rampart
The stratum corneum is the outermost part of the epidermis. It is composed of dead cells called corneocytes, surrounded by lipids such as ceramides, free fatty acids, and cholesterol.
The stratum corneum is often equated with the skin barrier as a whole. In reality, the skin barrier comprises three distinct components:
• The stratum corneum: a keratin structure that forms the scaffold
• Intercellular lipids: provide impermeability
• The hydrolipidic film: protects the surface and regulates pH
This structure is often compared to a brick wall. Corneocytes are the bricks, and lipids act as the mortar. When this structure is intact, skin retains water effectively and resists external irritants.
This is where a barrier cream, a nourishing cream, or a ceramide-rich treatment delivers its full value. This type of product aims to reinforce skin comfort, limit dehydration, and support a compromised barrier.
The skin microbiome: the invisible guardian of the barrier
The skin microbiome is an ecosystem of micro-organisms living on the skin's surface. It plays a fundamental role in skin protection and pH regulation.
A balanced microbiome contributes to:
• protecting against pathogenic bacteria
• limiting inflammation
• maintaining skin balance
• supporting the hydrolipidic barrier
The granular layer: producing protective lipids
Beneath the stratum corneum lies the granular layer. It plays an essential role in the formation of the skin barrier. Cells in this layer produce lipids that are released into the stratum corneum.
These lipids strengthen the skin's impermeability and limit water loss. A functional granular layer therefore directly contributes to skin hydration.
The spinous layer: cohesion and resilience
The spinous layer sits beneath the granular layer. It is composed of keratinocytes connected by structures called desmosomes. These connections give the skin its cohesion.
This layer also participates in keratin production and immune defense. It plays an important role in the epidermis's resilience against external aggressors.
A serum has a lightweight texture. It crosses the stratum corneum more easily and hydrates the intermediate layers of the epidermis.
A serum therefore hydrates the epidermis in depth, while a cream protects the skin barrier.
The basal layer: the engine of cell turnover
The basal layer is the deepest sub-layer of the epidermis. It contains stem cells that produce new skin cells.
These cells gradually migrate toward the surface. During this journey, they transform until they become the dead cells of the stratum corneum. This cycle lasts approximately 28 days.
The basal layer also contains melanocytes, which are responsible for melanin production.
The importance of exfoliation for the epidermis
Over time, dead cells accumulate in the stratum corneum. This accumulation prevents skincare products from penetrating properly.
Exfoliation removes these dead cells and thins the stratum corneum. Serums can then reach the granular and spinous layers more easily.
After exfoliation, skin becomes smoother and hydration more effective. Conversely, excessive exfoliation can weaken the skin barrier. We therefore recommend gentle exfoliation just once or twice a week.
To learn more about the different types of exfoliation.
The dermis: the layer of collagen and the lymphatic network
Beneath the epidermis lies the dermis, a deeper, denser layer that contributes to the skin's structure. The dermis is often at the heart of concerns related to firmness, suppleness, and the visual density of the skin.
It contains collagen, elastin, a significant portion of the skin's water, blood vessels, and other support structures.
It contains:
• collagen
• elastin
• hyaluronic acid
• blood vessels
• lymphatic network
The dermis is divided into two sub-layers.
The papillary dermis
The papillary dermis is the most superficial part of the dermis. It is rich in blood capillaries that supply nutrients and oxygen to the epidermis.
This zone is also where the lymphatic network begins. This network allows the elimination of cellular waste and excess fluid.
Good circulation in this zone contributes to skin radiance.
The reticular dermis
The reticular dermis is deeper and denser. It contains the majority of collagen and elastin fibers. This zone is responsible for skin firmness.
With age, collagen production declines. The dermis thins and skin loses density.
The majority of the skin's water is found in the dermis. Hyaluronic acid acts like a sponge capable of retaining this water.
Where collagen supplements act
Creams and serums only partially reach the dermis. Their action on this layer remains indirect, as the skin barrier limits molecular penetration. This is why internal support becomes particularly interesting when seeking to act on skin firmness and elasticity.
Collagen taken as a dietary supplement follows a completely different mechanism. Once ingested, it does not remain in the form of large collagen fibers. It is first digested in the stomach and intestine into collagen peptides, meaning small fragments composed of specific amino acids such as glycine, proline, and hydroxyproline.
These peptides are then absorbed into the bloodstream. They are transported to various tissues, including the dermis. Once in this layer, they act in two ways:
• they provide amino acids necessary for collagen synthesis
• they stimulate fibroblasts, the cells responsible for producing collagen and elastin
This stimulation of fibroblasts contributes to restarting endogenous collagen production. The dermis can thus progressively regain density and resilience.
Collagen also contributes to improving deep hydration. By supporting the extracellular matrix of the dermis, it promotes water retention linked to the hyaluronic acid naturally present in this layer. Skin then appears more plump.
Unlike creams, collagen supplements do not pass through the epidermis. They act directly from within, via the bloodstream. This approach allows action on the reticular dermis, where the fibers responsible for firmness are located.
The effects of oral collagen are not immediate. Dermal collagen renewal is progressive. Regular intake over several weeks is generally necessary to observe visible changes, particularly in elasticity, suppleness, and the appearance of wrinkles.
This approach therefore complements the action of topical treatments. Serums and creams act on the surface to hydrate and protect, while collagen acts in depth to support the internal structure of the skin.
To learn more about collagen as a dietary supplement
The hypodermis: the deep support layer
The hypodermis, also known as subcutaneous tissue, is the deepest layer. It is composed primarily of adipocytes, connective tissue, and blood vessels. This layer supports facial volume.
With age, the hypodermis thins. Tissues lose their support, which contributes to skin sagging.
Why massaging the hypodermis matters
Massage mechanically stimulates deep tissues. It improves blood and lymphatic circulation. This stimulation promotes nutrient delivery to the dermis and mobilizes the tissues of the hypodermis.
Massage also helps reactivate lymphatic drainage located in the dermis. This allows the elimination of waste and a reduction in puffiness.
It therefore acts on:
• the lymphatic network of the dermis
• blood circulation
• the tone of the hypodermis
How skincare products act according to skin layers
1. Exfoliation
If skin texture appears uneven or dull, a gentle exfoliant can be used periodically to smooth the skin's surface without weakening the barrier.
2. Serum
→ penetrates the epidermis
→ reaches the intermediate layers
→ hydrates more deeply
3. Cream
→ acts primarily on the stratum corneum
→ protects and locks in hydration
→ reinforces the skin barrier
4. Marine collagen supplement
→ acts via the bloodstream
→ influences the dermis
5. Massage
→ stimulates circulation
→ influences the hypodermis
This complementarity allows action across the entire skin.
Why combining multiple actions matters
Focusing only on the skin's surface is not enough to achieve lasting results. Skin is an organ structured in multiple layers, each with a specific role. A coherent routine must therefore act at different levels to support the entire skin structure.
Exfoliation acts first on the stratum corneum. By removing dead cells that have accumulated on the surface, it thins the skin barrier and allows subsequently applied products to penetrate the epidermis more effectively. Without this step, even the best actives can remain on the surface with reduced efficacy.
A serum then acts on the intermediate layers of the epidermis. Thanks to its lighter texture and smaller molecular size, it crosses the stratum corneum more easily. It hydrates the epidermis, improves skin suppleness, and prepares the skin for the next steps.
A cream acts primarily on the surface. It reinforces the skin barrier and limits water loss. Its role is to seal in the hydration delivered by the serum and protect the skin from external aggressors. An intact skin barrier helps maintain stable hydration and prevents chronic dehydration.
Collagen as a dietary supplement acts at a deeper level. It supports the dermis from within by stimulating collagen production and improving the structure of the skin matrix. This action contributes to maintaining skin firmness and elasticity, two factors that cannot be improved by surface-applied treatments alone.
Facial massage acts even more deeply. It stimulates blood circulation in the dermis, activates lymphatic drainage, and mobilizes the tissues of the hypodermis. This stimulation promotes nutrient delivery, improves oxygenation, and helps maintain the tone of deep tissues.
A coherent routine therefore works as a multi-layer approach. Exfoliation prepares the surface, the serum hydrates the epidermis, the cream protects the skin barrier, collagen supports the internal structure of the dermis, and massage stimulates the deep tissues of the hypodermis.
By combining these complementary actions, you act on the skin as a whole, from the surface down to the deepest layers. This global approach allows for more lasting improvement in hydration, firmness, elasticity, and radiance.