Skin Barrier Dysfunction in Eczema & Psoriasis: The Filaggrin Deficit, Ceramide Loss & How to Repair It
"Skin barrier" is used constantly in eczema and psoriasis content — often as a vague explanation for why these conditions involve dryness and sensitivity. Understanding what the skin barrier actually is, and specifically how eczema and psoriasis affect it differently, makes every other aspect of managing these conditions more comprehensible.
What the skin barrier is and how it works
The skin barrier is the outermost layer of skin — the stratum corneum — which consists of flattened, keratin-filled dead skin cells (corneocytes) embedded in a lipid matrix of ceramides, cholesterol, and fatty acids. The analogy used in dermatology is a brick-and-mortar wall: corneocytes are the bricks, and the surrounding lipid matrix is the mortar that holds them together and makes the wall waterproof.
This structure serves two simultaneous functions:
Outside-in protection: preventing allergens, bacteria, pollutants, and irritants from penetrating the deeper living layers of skin.
Inside-out retention: preventing water from evaporating out of the skin through a process called transepidermal water loss (TEWL). Healthy skin has low TEWL — the barrier holds water effectively. Damaged or compromised skin has elevated TEWL — water escapes at an accelerated rate, producing the dryness, tightness, and cracking characteristic of both conditions.
The lipid matrix is the most critical component of barrier function. It consists primarily of ceramides (approximately 50% of the lipid content), cholesterol (approximately 25%), and fatty acids (approximately 15%). These three components in the correct ratio produce an organised, lamellar (layered) lipid structure that is effectively waterproof.
Skin Barrier, Eczema & Psoriasis: Why Barrier Health Matters So Much
If you’ve researched eczema or psoriasis online recently, you’ve probably seen the phrase “skin barrier” everywhere.
That’s because researchers and dermatologists increasingly believe skin barrier dysfunction sits at the centre of many inflammatory skin conditions — especially eczema and psoriasis.
When the skin barrier becomes weakened, the skin may:
Lose moisture more easily
Become irritated faster
Feel itchy and tight
React more strongly to products and environments
Struggle to recover from inflammation properly
And for people with eczema or psoriasis, this barrier dysfunction often becomes part of a frustrating flare-up cycle.
Supporting the skin barrier consistently is one of the most important long-term habits for eczema and psoriasis-prone skin.
How eczema affects the barrier: the filaggrin-primary defect
Eczema's primary barrier defect is in the protein component of the barrier rather than the lipid matrix alone. The most significant genetic factor in atopic eczema is mutations in the filaggrin gene (FLG). Filaggrin is a structural protein that binds keratin filaments together inside corneocytes, helping flatten them into the compact shape that makes them effective barrier bricks. Filaggrin is also broken down into the natural moisturising factor (NMF) components that maintain the skin's surface acidity and hydration.
FLG mutations therefore produce two simultaneous problems: corneocytes that are structurally compromised (imperfect bricks), and reduced NMF that fails to maintain surface hydration and appropriate skin pH. This explains why eczema skin is prone to alkalinity — a higher pH that itself disrupts ceramide processing enzymes, further damaging the lipid mortar in a self-amplifying cycle.
The ceramide content of eczema skin is also specifically reduced — both because the structural protein defect disrupts ceramide processing and because Th2 cytokines (IL-4, IL-13) directly downregulate ceramide-producing enzymes. The combined protein and lipid defect produces a highly permeable barrier that loses water rapidly and allows allergens to penetrate — which is why atopic eczema is associated with sensitisation to food and environmental allergens.
How psoriasis affects the barrier: a different primary defect
Psoriasis's barrier disruption is secondary to its primary pathology rather than the primary cause. In psoriasis, accelerated keratinocyte turnover produces corneocytes that haven't completed their full differentiation cycle — they reach the surface incompletely keratinised and with altered lipid composition. The psoriatic plaque scale consists of these abnormally differentiated, partially cornified cells.
The lipid composition of psoriatic stratum corneum is specifically abnormal: ceramide ratios are altered, with reduced ceramide 1 (which is particularly important for barrier organisation), and cholesterol synthesis is upregulated. This produces a structurally different and less functional barrier than healthy skin — different from eczema's ceramide deficit but producing similarly elevated TEWL in affected areas.
Critically, psoriatic skin even outside visible plaques has measurably elevated TEWL compared to healthy skin — suggesting the barrier defect is more widespread than just the plaques themselves..
Why the eczema and psoriasis barrier defects are different in practice
The distinction matters for treatment approach:
For eczema: barrier repair products containing ceramides directly address a documented ceramide deficit. Emollient formulations incorporating ceramide, cholesterol, and fatty acids in the ratio found in healthy skin (roughly 3:1:1) are mechanistically targeted rather than just generally moisturising. Vitamin D supplementation has specific relevance because it upregulates filaggrin expression — addressing the primary genetic defect rather than just compensating for its consequences.
For psoriasis: emollient support reduces TEWL and improves surface comfort, but the primary driver of barrier disruption is the ongoing keratinocyte hyperproliferation — which only appropriate treatment (topical vitamin D analogues, topical steroids, phototherapy, systemic treatments) addresses. No emollient can repair the barrier disruption that continues while active disease is present; emollient's role is reducing the surface consequences.
What damages the barrier further in both conditions
Hot water — heat disrupts the lipid bilayer structure of the stratum corneum, increasing TEWL and accelerating the barrier breakdown.
Sodium lauryl sulphate (SLS) — a detergent in many cleansers that directly extracts the ceramides and cholesterol from the stratum corneum, disrupting the lipid mortar. Fragrance-free, SLS-free cleansers are non-negotiable for both conditions.
Fragrance — fragrance compounds penetrate compromised barriers more readily and trigger contact sensitisation. For eczema-prone skin where barrier permeability is already elevated, this is a primary concern.
Over-exfoliation — acids and physical exfoliants remove the outermost corneocyte layers, reducing the barrier depth and increasing permeability.
Stress — as covered in the stress article in this series, cortisol directly downregulates ceramide synthesis, specifically damaging the lipid mortar component of the barrier. This is one of the mechanisms through which psychological stress worsens both conditions.
What actually repairs the skin barrier
Consistent emollient application — the most directly effective intervention. Applied within two to three minutes of bathing, emollient reduces TEWL by providing an occlusive or semi-occlusive layer that slows water evaporation. Purpose-formulated emollients containing ceramides, cholesterol, and fatty acids provide both occlusive protection and direct replacement of barrier lipids.
Treating the underlying condition — the most important intervention for sustained barrier repair in both eczema and psoriasis. Emollient compensates for barrier dysfunction; treating the inflammatory condition reduces the ongoing damage that makes emollient a perpetual necessity.
Vitamin D — for eczema specifically, vitamin D upregulates filaggrin expression, addressing the primary protein defect rather than just compensating for it. Covered in detail in the vitamin D and eczema article.
Zinc — supports keratinocyte function and the enzymatic processing of barrier proteins. Lower zinc status correlates with worse eczema, in part through barrier-relevant mechanisms.
Avoiding barrier stressors — SLS-containing cleansers, fragrance, hot water, and over-exfoliation.
Why Moisture Loss Matters
One major feature of barrier dysfunction is increased transepidermal water loss (TEWL) — where water escapes through the skin too quickly.
This may leave the skin feeling:
Dry
Tight
Dehydrated
More prone to cracking and itching
Researchers believe reducing moisture loss is one of the most important goals in eczema and psoriasis care.
Hydration and barrier protection work closely together.
Why Moisturising Is So Important
Moisturisers help support the skin barrier by:
Reducing water loss
Softening dry skin
Improving comfort
Protecting against irritation
Different moisturisers work differently:
Humectants attract water
Emollients soften the skin
Occlusives help seal moisture in
Consistent moisturising is one of the simplest but most important barrier-support habits.
Recommended Products
CeraVe Moisturising Cream
a ceramide-containing emollient providing ceramides 1, 3, and 6-II alongside hyaluronic acid in a fragrance-free, dermatologist-tested base. As covered above, eczema skin is specifically short of ceramides — a formulation providing them directly addresses the documented lipid deficit rather than simply providing occlusion. One of the most consistently recommended emollients for compromised barrier skin
Cetaphil Gentle Skin Cleanser
a fragrance-free, soap-free, SLS-free cleanser that cleans without extracting the ceramides and cholesterol from the stratum corneum that SLS-containing products remove. As covered above, SLS remains in contact with skin cells even after rinsing and sustains barrier disruption beyond the wash itself. A consistent fragrance-free, SLS-free cleanser is the most impactful single product choice for barrier-compromised skin.
Why Overdoing Skincare Often Backfires
One of the biggest modern skincare mistakes is overloading the skin with active ingredients.
Too many acids, exfoliants or harsh products may:
Strip natural oils
Increase irritation
Trigger inflammation
Weaken the barrier further
This is especially common in people trying to aggressively “fix” acne, dryness or texture issues.
More skincare products doesn’t always mean healthier skin.
Stress, Sleep & The Skin Barrier
Researchers increasingly link stress and poor sleep to weakened skin barrier recovery.
Poor recovery may affect:
Inflammation
Skin hydration
Overnight repair
Itching and flare-ups
This is one reason eczema and psoriasis often worsen during stressful or exhausting periods.
Skin barrier health is connected to overall recovery and wellbeing too.
Supplement Support for Dry, Sensitive Skin
The nutritional foundations of barrier function — vitamin D for filaggrin expression, zinc for keratinocyte support, omega-3s for membrane lipid composition, vitamin C for collagen and barrier protein synthesis — address the barrier at the cellular level that topical products cannot fully replace.
Drought's Skin Support Formula provides vitamin D, zinc, vitamin C, magnesium, and 10 other nutrients selected for their roles in skin barrier function and immune regulation — addressing the internal nutritional dimensions of barrier repair that emollient alone cannot cover. Made in the UK, suitable for vegetarians, designed for consistent long-term daily use.
FAQ
What is the skin barrier and why does it matter for eczema and psoriasis?
The skin barrier is the outermost layer of the stratum corneum — a structure of protein-rich corneocytes (the "bricks") held together by a ceramide-rich lipid matrix (the "mortar"). Its two primary functions are preventing transepidermal water loss (TEWL) and blocking allergen and irritant penetration. In eczema, this structure is fundamentally compromised at a genetic level — filaggrin loss-of-function mutations reduce the natural moisturising factors and ceramide precursors that maintain the lipid matrix, creating gaps through which water escapes and allergens penetrate simultaneously. In psoriasis, immune-driven keratinocyte hyperproliferation disrupts normal cornification, producing the thick abnormal scale rather than the moisture loss that defines eczema — a different barrier problem through a different primary mechanism.
Why is eczema linked to skin barrier dysfunction?
Filaggrin is the most important single explanation. The FLG gene encodes filaggrin — a protein required for natural moisturising factor production, stratum corneum acidification, and cornified envelope formation. Loss-of-function FLG mutations are present in approximately 10% of European populations and in 25–50% of people with atopic eczema — the strongest known genetic risk factor for the condition. Filaggrin deficiency reduces NMF by 50% or more, increases TEWL to approximately double the rate of healthy skin even between flares, and disrupts the acidic pH that keeps skin-degrading serine proteases inactive. The result is structurally deficient skin that is fundamentally different from simply dry skin — which is why eczema requires barrier repair rather than just moisturising.
What is TEWL and why does it matter for eczema?
TEWL — transepidermal water loss — is the rate at which water evaporates through the skin. Healthy skin maintains TEWL at a rate that keeps the stratum corneum adequately hydrated. Eczema skin loses water at approximately twice the rate of healthy skin even between flares, and up to four times the rate during active flares — driven by the ceramide deficit and filaggrin loss that compromise the lipid matrix sealing water in. This accelerated water loss creates the dryness, tightness, and itch cycle that defines eczema's day-to-day experience independently of active inflammation. Reducing TEWL through occlusive emollient application is the most directly relevant topical management goal — more important than adding moisture that will immediately evaporate through the compromised barrier without an occlusive layer.
Why are ceramides important for eczema and psoriasis?
Ceramides are the primary lipid component of the stratum corneum lipid matrix — accounting for approximately 50% of the lipids between corneocytes. Eczema skin has 30–40% lower ceramide content in the stratum corneum than healthy skin — a deficit that creates the gaps through which water escapes and contact allergens penetrate. This is the mechanism that explains why ceramide-containing emollients (CeraVe, Cetraben, Epaderm) are more specifically appropriate for eczema than petrolatum alone — they replace what is structurally missing rather than simply occluding the surface. Ceramide production is regulated by vitamin D through VDR-mediated transcription — one of the most specific mechanisms connecting vitamin D deficiency to eczema severity.
Is skin barrier dysfunction in eczema different from psoriasis?
Yes — and the distinction matters practically. Eczema's barrier dysfunction is primarily genetic and structural — filaggrin mutations and ceramide deficit create the initial barrier failure that allows allergen sensitisation and inflammatory cascade, meaning the inflammation follows from the barrier failure. Psoriasis's barrier disruption is primarily immune-driven — the Th17 T-cell mediated keratinocyte hyperproliferation disrupts normal cornification, producing the thick adherent scale characteristic of plaques rather than the moisture loss and allergen penetration that characterise eczema. For eczema, barrier repair is primary management. For psoriasis, immune modulation is primary management — barrier support addresses the secondary scale and dryness rather than the underlying immune driver.
What damages the skin barrier and how quickly does it recover?
The most consistently barrier-damaging practices are over-cleansing with high-pH alkaline surfactants (disrupting the acid mantle that keeps serine proteases inactive), over-exfoliation with AHAs and physical exfoliants (accelerating stratum corneum removal faster than it regenerates), excessive hot water exposure (solubilising the ceramide lipid matrix), and fragrance contact allergens (triggering Type IV delayed hypersensitivity that disrupts tight junctions). In healthy skin, barrier recovery after significant disruption takes approximately 3–5 days — the time required for new ceramide synthesis and corneocyte formation. In eczema-prone skin with the underlying filaggrin and ceramide deficit, barrier recovery takes significantly longer and is never complete — which is why consistent protective emollient use during and between flares is more effective than reactive application during flares only.
How do you repair the skin barrier with eczema or psoriasis?
The most evidence-based approach combines occlusive protection with ceramide replacement and upstream nutritional support. Ceramide-containing fragrance-free emollients applied within two to three minutes of bathing (while the stratum corneum is still hydrated from water contact) seal ceramide alongside existing surface moisture rather than applying dry emollient to already-dry skin. Vitamin D's VDR-mediated ceramide synthesis upregulation and filaggrin expression regulation addresses the barrier deficit from within — the most specific nutritional intervention available for eczema's core structural problem. Zinc's tight junction repair and keratinocyte support addresses the secondary permeability pathway that ceramide replacement alone doesn't close. Avoiding further barrier damage through fragrance elimination, pH-appropriate gentle cleansers, and temperature reduction is as important as active repair — the barrier cannot recover while it is being continuously disrupted.
Summary
The skin barrier is the outermost layer of skin — corneocytes (the bricks) embedded in a ceramide-cholesterol-fatty acid lipid matrix (the mortar) — that simultaneously prevents water loss and blocks external penetration. Eczema's primary barrier defect is in filaggrin protein and ceramide synthesis, producing a structurally compromised, permeable barrier. Psoriasis's barrier disruption is secondary to keratinocyte hyperproliferation, producing abnormally differentiated cells with altered lipid composition. Both conditions have elevated TEWL. Emollient supports the barrier by reducing water loss; treating the underlying inflammatory condition addresses the primary driver of ongoing damage. Vitamin D (filaggrin upregulation) and zinc (keratinocyte support) address the nutritional dimensions of barrier repair from within.
Written by the Drought Skin team — specialists in natural support for psoriasis, eczema and acne
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Moisturising for Eczema: How to Do It Properly & What Actually Works
Vitamin D and Eczema: What the Evidence Actually Shows
Zinc for Eczema: How It Works, What the Evidence Shows & the Right Dose
How Stress Triggers Eczema & Psoriasis Flare-Ups
Emollients for Psoriasis: Which Type Works Best & How to Use Them
