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What is a Moisturiser and How Can it Help with Skin Health
As an esthetician, I find it interesting that few dermatology textbooks devote much space to this subject.
No standard definition really exists.
Yet we use and recommend moisturisers daily.
So join me as I decode what a moisturiser is.
How it works on the skin, and how to choose one that supports barrier strength, hydration, and long-term resilience.
Key takeaways
A moisturiser supports skin by repairing the barrier, improving hydration, reducing transepidermal water loss (TEWL), and replenishing lipids.
The most effective formulas combine humectants, emollients, and occlusives (and ideally, skin-identical lipids such as ceramides, cholesterol, and fatty acids).
If your skin is dry, sensitised, reactive, or post-treatment, moisturiser choice becomes l “ss “cosm “tic” and more physiological.
IN THIS ARTICLE
What Is a Moisturiser?
Technically, a moisturising treatment involves a four-step process:
- Repairing the skin barrier
- Increasing water content in the outer layer of skin (stratum corneum)
- Reducing transepidermal water loss (TEWL)
- Restoring the barrier’s ability to attract, hold, and redistribute water
In other words, a good moisturiser helps skin behave like healthy skin again — calm, resilient, and comfortably hydrated.
What Moisturisers Do for the Skin
Depending on your skin type and concerns, moisturisers may help to:
- Replenish natural oils on the skin’s surface
- Support barrier function and reduce the look of irritation
- Soften and smooth texture for a more supple, youthful feel
- Deliver antioxidants to reduce oxidative stress
- Use humectants to lock in hydration and slow evaporation
- Support the acid mantle and skin comfort with gentle, barrier-friendly formulas
- Fill micro-fissures between skin cells, reinforcing a stronger outer layer
How Do Moisturisers Work?
Traditionally, moisturisers were believed to work mainly by reducing transepidermal water loss.
Water begins in deeper epidermal layers and moves upward to hydrate cells in the stratum corneum (the outer layer), before being lost to evaporation.
The bricks-and-mortar model explains why moisturiser choice matters so much. Your skin cells are the bricks. The lipids between them are the mortar.
When intercellular lipids such as ceramides, cholesterol, and fatty acids become depleted, barrier function weakens — and skin becomes more prone to dryness, awareness, inflammation, and sensitivity.
For a ceramide-focused deep dive, you can link here: 6 Barrier Healing Benefits of a Ceramide Moisturiser.
The skin also contains Natural Moisturising Factor (NMF) — a blend of amino acids, lactates, urea, and electrolytes that helps the stratum corneum retain water.
Dry skin typically occurs when the moisture content drops below roughly 10%. Using humectants and layering with occlusives helps prevent ongoing loss, as discussed by the American Academy of Dermatology: How to choose a moisturiser.
Components That Make a Moisturiser
Occlusives
Occlusives form a film on the skin’s surface, helping reduce TEWL and prevent water evaporation from the stratum corneum.
If you want a full breakdown of occlusive ingredients in moisturisers, click here: Occlusive ingredients in moisturisers.
Humectants
Humectants attract water into the outer layer of skin, improving hydration and comfort.
NMF-aligned humectants include glycerin, sorbitol, urea, amino acids, sodium PCA, and alpha hydroxy acids such as lactic acid.
Continued evaporation from skin can exacerbate dryness, which is why we often suggest layering a humectant-based product (hydration) with an occlusive or lipid-rich step (barrier protection).
Hydration internal link: H₂O Hydrating Skin Shot
Emollients
Emollients immediately improve texture by smoothing roughness and filling the gaps between skin cells — like mortar between bricks.
Essential fatty acids (such as linoleic acid) support barrier function, membrane fluidity, and skin signalling.
Recommended: Fortify Barrier Repair Cream
Fortify is a restorative barrier moisturiser formulated with skin-identical lipids to support a stronger, calmer skin barrier. It helps reduce tightness, improve hydration retention, and soothe dryness when skin feels sensitised, reactive, or environmentally stressed.
Best for: Dry, combination, sensitive or reactive skin; barrier disruption; post-treatment recovery; and compromised skin needing lipid support.
Recommended: XCELL Barrier Repair Skin Shot
XCELL is a targeted lipid-rich treatment designed to reinforce barrier resilience and support recovery when skin is dry, red, or prone to irritation. It helps improve skin comfort, calm sensitivity, and support a more balanced inflammatory response.
Best for: Barrier disruption, inflammation, post-treatment sensitivity, reactive or breakout-prone skin, dryness, and environmental stress.
Moisturisers and Collagen
Collagen and other proteins (such as keratin and elastin) are often marketed as “rejuvenating” when applied topically. In reality, protein molecules are typically too large to penetrate deeply.
They may temporarily smooth the skin by forming a thin film, but they don’t rebuild dermal collagen as marketing often suggests.
Alpha Hydroxy Acids
Alpha hydroxy acids (such as glycolic and lactic acid) have small molecular structures and can help dissolve surface cell build-up that contributes to roughness and dullness.
Used appropriately, they can help achieve smoother-looking skin—but barrier function should always come first if your skin is reactive or dry. You’d like to link a broader ingredient guide; this internal read works beautifully here: The best moisturising ingredients for dry skin.
Samantha Miller is the founder of The Naked Chemist and has over 30 years of hands-on experience working directly with skin.
A qualified clinical aromatherapist and holistic skin therapist, Samantha specialises in barrier repair, sensitive skin, and evidence-informed ageing support — creating results-driven formulations designed to help compromised skin return to true health.
To Conclude: The Naked Truth
Moisturisers are not optional extras. They’re one of the simplest, most effective tools we have for supporting skin comfort, resilience, and barrier strength. When you understand what a moisturiser is and how it works — barrier repair, hydration support, reduced TEWL, and lipid replenishment — you can choose products based on skin physiology rather than marketing noise.
Healthy skin behaves like healthy skin when the barrier is supported consistently. That’s where the right moisturiser quietly does the heavy lifting.
FAQs
1) What is a moisturiser?
A moisturiser is a topical product designed to support the skin barrier, improve hydration in the outer layer of skin, and reduce transepidermal water loss (TEWL). The best formulas help skin “ay “”alm” rather than “an “re” ct.”
2) Do moisturisers add water to skin or stop water loss?
Most do both. Humectants increase water content in the stratum corneum, while occlusives slow evaporation. Barrier lipids (like ceramides, cholesterol, and fatty acids) reinforce the structure, so hydration can actually stay put.
3) Should oily or acne-prone skin use a moisturiser?
Yes. Oily skin can still have a damaged barrier. A lightweight, barrier-friendly moisturiser can improve tolerance, reduce inflammation, and support calmer skin behaviour.
4) When should you apply moisturiser in a routine?
Apply after hydration (like a humectant serum) and before SPF in the morning. At night, apply as your final step — or layer over hydration if skin feels tight or dehydrated.
5) What ingredients should I look for in a barrier-support moisturiser?
Look for humectants (glycerin, urea, sodium PCA), emollients (skin-softening lipids), and occlusives. For compromised or reactive skin, skin-identical lipids such as ceramides, cholesterol, and fatty acids are especially supportive.
6) How long does it take to see results from a good moisturiser?
Comfort can improve within days, but true barrier restoration often takes a few weeks of consistent use — especially if skin has been sensitised by over-exfoliation, harsh cleansing, or intensive treatments.