Why moisturisation may only tell us half the hydration story
Hydration has become one of skincare’s universal promises. From serums and moisturisers to masks and mists, we have become very good at talking about how to give skin more moisture. And for good reason. Hydration influences how skin feels, how it looks and how we perceive its health.
Before asking how much moisture we can give the skin, it is worth considering what allows healthy skin to hold onto that moisture in the first place.
The answer takes us beyond water itself and towards the architecture of the stratum corneum. Here, corneocytes are surrounded by an extracellular lipid matrix composed principally of ceramides, cholesterol and free fatty acids. Arranged into highly organised lamellar structures, these lipids form an essential part of the barrier that helps regulate water loss.
In simple terms, hydrated skin doesn’t just need water. It needs an effective way of keeping it there.
When that lipid environment becomes depleted or its organisation changes, the effects can eventually become visible at the surface: dryness, roughness and skin that feels less resilient. Underneath those familiar signs, however, is a story about structure as much as moisture.
Moisturisation remains important. But understanding how skin retains moisture gives us another part of the picture.
Looking Beyond Moisture
For formulators, this opens up another way of thinking about hydration. Humectants remain important for attracting and binding water, while emollients and occlusive materials play valuable roles in softening the skin and limiting moisture loss. None of those fundamentals need to change. Supporting the conditions that help skin remain hydrated brings lipid architecture into the formulation conversation too.
The familiar “bricks and mortar” analogy helps us visualise why. Corneocytes form the bricks, while extracellular lipids are often described as the mortar between them. It is a useful image, but one that can make those lipids sound rather passive, simply filling the spaces between cells.
There is much more happening in the mortar.
Ceramides, cholesterol and free fatty acids are organised into highly ordered lamellar structures within the stratum corneum. Their presence matters, but so does their composition and organisation. Together, they contribute to the permeability barrier that helps control the movement of water through the skin. For formulators, this raises a more useful question than simply whether a formulation contains lipids:
What are those lipids doing within the wider biology of the barrier?
From Lipid Presence To Lipid Architecture
AvenaPLex® is an oat-derived active lipid complex containing naturally occurring phytoceramides, phospholipids, sterols and free fatty acids. Its multi-lipid profile provides a way of approaching the skin barrier through components relevant to its natural lipid environment. Its composition explains why AvenaPLex may be of interest to barrier-focused formulation, but composition alone cannot tell us what happens once it meets the skin.
In a human skin explant model, AvenaPLex was shown to increase epidermal lipid content by up to 60% over five days. Separate analysis also demonstrated a 14% increase in intercellular lipid lamellae organisation, providing evidence across both lipid abundance and organisation.
There is a functional side to the evidence as well. In vivo testing with 1% AvenaPLex demonstrated a 9% reduction in transepidermal water loss within one hour, providing evidence of rapid barrier-function support.
These findings come from separate studies, so they should not be interpreted as a demonstrated causal sequence. Taken together, however, they allow us to look at three distinct aspects of barrier biology: lipid abundance, lipid organisation and water loss.
*Study conditions and models vary. See the AvenaPLex® Data Pack for full study details.
From Hydration To Well-Ageing
As skin ages, the lipid environment of the stratum corneum changes too. Levels of important barrier lipids, including ceramides, can decline, while cumulative environmental pressures place additional demands on skin over time.
Dryness may be one of the things we notice at the surface, but it is only one part of a broader change in the way skin functions as it ages. This gives lipid architecture relevance beyond hydration alone.
Supporting the structures and processes involved in healthy barrier function can also form part of a wider approach to maintaining healthy skin over time.
For AvenaPLex, its oat-derived lipid complex and evidence across epidermal lipid content, lipid organisation and barrier function provide a way to explore well-ageing from the structure of the skin outwards.
Healthy skin already has sophisticated ways of managing water, maintaining its barrier and organising the lipids within it. Understanding those systems gives us another way to think about what we ask a formulation to do.
AvenaPLex®. Rebuild skin with what it knows.
