Common misconceptions about the skin barrier.

False.

The skin barrier does not breathe in the biological sense of the term. Unlike the lungs, it does not absorb oxygen from the air to redistribute it to cells. The oxygen used by keratinocytes and fibroblasts originates from the blood circulation in the dermis, not from the external environment. The confusion arises because the skin does exchange with its surroundings by allowing certain lipophilic molecules to pass through the stratum corneum, but this diffusion is very limited. Therefore, saying that the skin "breathes" is a misleading metaphor.

This myth often fuels the fear that creams or makeup can "suffocate" the skin. In reality, the only risk with very rich or occlusive products is clogging the pores, those tiny openings connecting the sebaceous glands to the surface of the epidermis. Sebum can then accumulate there, form a plug, and promote the appearance of blemishes, especially in oily skin. However, this phenomenon has nothing to do with skin that "can't breathe": the skin barrier is never truly smothered, even when the skin appears dull.

True and false.

It is an oversimplification to equate the skin barrier with the hydrolipid film. In reality, the skin barrier corresponds to the combination of the hydrolipid film and the intercellular lipid layer present in the stratum corneum. The hydrolipid film is a thin superficial film composed of sebum and sweat, which provides immediate protection against external aggressions and contributes to the hydration of the skin surface. The intercellular lipids, on the other hand, structure the stratum corneum and, together with the hydrolipid film, limit water loss and the entry of pathogens. These two components play complementary roles in the skin’s barrier function.

False.

The skin barrier has functions beyond preventing water loss. In addition to this role, it helps protect the skin from invading pathogens such as bacteria, viruses, or fungi, thereby reducing the risk of infection and inflammation. The intercellular lipids of the stratum corneum and the hydrolipidic film actively contribute to this defense by forming a physical and chemical barrier, that regulates what can penetrate the skin.

Good to know : Beyond its role as a barrier against dehydration and microbes, the skin performs numerous essential functions. It contributes to immune response, sensory perception, thermoregulation, and vitamin D synthesis...

False.

The skin microbiota plays a central role in the health and resilience of the skin barrier. This complex ecosystem, composed of bacteria, yeasts, and viruses residing on the surface of the skin, continuously interacts with keratinocytes and immune cells. These interactions contribute to the regulation of inflammation and the maintenance of an acidic pH. Moreover, commensal bacteria, such as Staphylococcus epidermidis, produce organic acids and antimicrobial substances that prevent the proliferation of pathogenic species, such as Staphylococcus aureus.

An imbalance in the microbiome, known as dysbiosis, conversely compromises the skin barrier and promotes inflammation. This is, for example, what occurs in certain forms of eczema, where microbial diversity decreases in favor of S. aureus, which stimulates immune responses. This process perpetuates inflammation and exacerbates water loss.

The microbiota can be considered a living extension of the skin barrier.

False.

Indeed, the skin barrier tends to weaken with age. Over time, the skin undergoes structural changes: thinning of the epidermis and dermis, reduced cell turnover, fewer and less active immune cells… These alterations lead to decreased cellular cohesion and repair capacity, making the skin more vulnerable to irritation, infection, and dehydration. We also observe a decrease in filaggrin production due to slowed cell renewal—a protein in the stratum corneum that aggregates corneocytes—and a low-grade chronic inflammation. Added to this are extrinsic factors such as UV exposure, which accelerate skin aging and further compromise barrier function.

However, despite these changes, it remains perfectly possible to maintain a healthy skin barrier as we age. Studies have shown that regular use of gentle cleansers, such as dermatological cleansing bars, and moisturizing and relipidizing treatments significantly strengthen the barrier’s integrity. Slightly acidic formulations containing ceramides, glycerin, or urea help limit xerosis and pruritus commonly seen in mature skin. Finally, the antioxidants topical ones can complete the skincare routine by supporting the skin’s natural defenses.

Aging does not imply an unavoidable loss of skin barrier function, provided that appropriate skincare is used.

False.

While the skin does indeed begin to repair itself rapidly after an insult, full restoration of barrier function requires much more time. In general, it takes approximately 3 weeks for the skin barrier to naturally recover its functional integrity, depending on the extent of the damage. The first few hours are devoted to reestablishing the continuity of the skin surface, but lipid rebuilding, pH normalization, and the restoration of cell cohesion proteins involve a longer, gradual process.

Scientific evidence

A study conducted on 32 healthy volunteers illustrated this slow pace of regeneration. Researchers created small 8 mm suction wounds on the forearm and then monitored their progress. Measurements showed that re-epithelialization was nearly complete after 8 days, but barrier function, assessed by water loss, only returned to normal after about three weeks. In addition, persistent changes, such as post-inflammatory hyperpigmentation and increased stiffness of the skin tissue, were observed up to 60 days after the injury. This suggests that the newly formed skin remains more vulnerable and potentially prone to further damage.

Tip : Regular application of moisturizing and healing skincare products can accelerate the regeneration of the skin barrier.

False.

The cosmetics require time and patience to deliver results. While some products can quickly enhance hydration and reduce water loss from the very first application, those effects primarily reflect a superficial and transient action. Moisturizing creams work by various mechanisms—mainly as humectants (holding water in the stratum corneum), emollients (supplying lipids), and occlusives (forming a protective film that limits evaporation). These actions help soothe discomfort and partially restore the skin barrier, but true structural repair—that is, the reestablishment of intercellular lipids and corneocyte integrity—cannot occur instantaneously.

Studies show that complete skin barrier restoration requires several days to several weeks of regular use of moisturizing skincare products. The most pronounced improvements in barrier function are typically observed after 2 to 4 weeks of daily application. Efficacy also depends on the product’s formulation and its suitability for a given skin type: ill-suited products can paradoxically further impair the skin barrier.

False.

A damaged skin barrier can be repaired, provided appropriate care products are used which support its physiological regeneration mechanisms. As the previously cited studies clearly illustrate: the regular application of moisturizing creams enriched with lipids, urea, or plant oils significantly improves hydration, reduces water loss, and restores the lipid composition of the stratum corneum, resulting in improved barrier function after a few weeks of use.

Scientific evidence

A clinical study examining a biphasic serum containing 17.5% plant oils, 61% water, 2% panthenol, 2.7% glycerin, and hyaluronic acid demonstrated the potential of this type of treatment to repair the skin barrier. The trial, conducted with 8 volunteers over 14 days, measured transepidermal water loss and changes in stratum corneum hydration. The table below shows the results obtained, which reflect a significant and rapid improvement in skin barrier function in the group using the biphasic serum, while no significant change was observed in the control group.

Note : For atopic-prone skin or skin affected by xerosis, barrier repair may be slower and more delicate due to chronic alterations of the hydrolipid film and a deficiency in lipids and natural moisturizing factors. However, even in these cases, targeted care can progressively enhance the integrity and function of the skin barrier.

False.

A weakened skin barrier is not always visible to the naked eye. Sensations of discomfort, such as tightness or warmth, can, for example, be a nonvisible sign. Moreover, numerous studies have shown that barrier function alterations can occur even on skin that appears normal, without redness, dryness, or apparent lesions. These dysfunctions are often detectable only with instrumental techniques, such as the measurement of transepidermal water loss (TEWL). For example, some individuals with eczema exhibit elevated TEWL or an altered lipid profile even in skin areas that look healthy.

Scientific evidence

Researchers in a study involving 22 children with atopic dermatitis and 40 healthy controls observed in the atopic group a significant increase in transepidermal water loss (TEWL) and a decrease in stratum corneum lipids, two indicators of impaired barrier function. Interestingly, TEWL was also elevated in apparently normal-looking skin (without visible lesions), albeit to a lesser extent than in eczematous areas. The squalene level, one of the main lipid components of sebum, was likewise reduced, including in these noninflamed regions.

Skin barrier dysfunction can precede visible signs, and skin that appears healthy may already harbor underlying fragility.

True and false.

It is true that the sensation of tightness very often arises from a disruption of the skin barrier. Indeed, when the cohesion between corneocytes decreases or the hydrolipidic film loses effectiveness, water evaporates more easily through the epidermis. At the same time, the skin becomes more permeable to irritating agents, stimulating cutaneous nerve endings, hence the sensation of tightness or even tingling. This phenomenon is particularly common after using overly harsh, detergent-based cleansers, during exposure to cold, wind, or low ambient humidity, or when the skin lacks sufficient lipids to maintain its barrier function, as can occur in xerosis.

Beyond a truly compromised skin barrier, the sensation of tightness can also originate from an allergic reaction. This reaction follows skin exposure to an allergen that triggers localized inflammation, without necessarily causing a structural breach in the barrier. Furthermore, in sensitive skin, discomfort can result from nervous system hyperactivity, again without any actual compromise of the skin barrier.

False.

It is entirely possible to have a compromised skin barrier, even with oily skin. This may seem counterintuitive at first glance: oily skin secretes sebum abundantly, which contributes to the hydrolipidic film. Located on the surface of the epidermis, this film limits water loss and helps maintain a balanced skin barrier. However, its effectiveness does not rely solely on the hydrolipidic film but also on the intercellular lipid layer of the stratum corneum. In some cases, this layer becomes disorganized in oily skin, leading to skin barrier alteration.

Scientific evidence

A recent study conducted on 47 subjects with oily, sensitive skin confirmed that this skin type indeed exhibits a measurable alteration of the skin barrier. The researchers analyzed several skin parameters – hydration, transepidermal water loss, sebum secretion, erythema – as well as the stratum corneum metabolome, corresponding to the full set of metabolites. The results showed a significant decrease in sphingolipids and ceramides, molecules that insert themselves between the cells of the stratum corneum to ensure their cohesion and the stability of the skin barrier.

For example, the concentration of sphingomyelin SM(d18:1/16:0) was reduced by nearly 68% in moderately sensitive oily skin and was virtually absent in highly sensitive oily skin. This decrease in structural lipids, whose cause was unidentified, was accompanied by an imbalance in amino acid and sphingosine metabolism, indicating an overall weakening of the skin barrier function.

In other words, even oily skin can suffer from latent inflammation and heightened sensitivity, demonstrating that excess sebum and an effective skin barrier do not always go hand in hand.

False.

The ceramides are not the only active ingredients capable of restoring the skin barrier, even though they are major components of it. The squalane, for example, strengthens the hydrolipidic film through biomimicry. Similarly, plant oils rich in fatty acids can bolster the hydrolipidic film and some may even integrate into the stratum corneum to enhance its cohesion. The natural moisturizing factors (NMF), a blend of amino acids and urea, help maintain water in the stratum corneum and can also aid in restoring the skin barrier.

Scientific evidence

Multiple studies have shown that ceramide-free formulations can significantly enhance skin barrier function. In particular, a clinical study was conducted on 25 individuals with dry, atopic skin. Over a three-week period, participants applied a cosmetic formulation with a physiological pH containing 10% urea and sweet almond and evening primrose oils.

The measurements demonstrated a significant improvement in skin hydration, a trend toward pH normalization, as well as a visible reduction in dryness. Lipid analysis of the stratum corneum revealed an increase in total lipid content, particularly of ceramides EOS, NP, and AP.

False.

No scientific evidence supports this idea; in fact, it’s quite the opposite. Washing your skin too often, especially with soap and water, weakens the skin barrier. Numerous studies show that each wash increases transepidermal water loss, raises the skin pH, and exacerbates redness and irritation. These effects are cumulative: the more you wash, the weaker the skin becomes. Therefore, repeated washing does not make the skin more resilient.

Scientific evidence

A study conducted with 15 volunteers illustrates this phenomenon. Each participant tested six different washing and drying techniques on the forearm, combining water or soap with drying by friction, patting, or evaporation. The researchers measured transepidermal water loss (TEWL), hydration, pH, and erythema after each step. The results are unequivocal: simply washing with water or soap increases TEWL, and this effect grows stronger with each successive wash.

For example, washing with soap followed by towel drying increased TEWL from 10.1 to 13.1 g/h·m² after just two washes. Even air-drying or pat-drying, often perceived as gentler, led to a marked increase in TEWL, reaching up to 30.1 g/h·m² in some cases. Moreover, skin pH, normally acidic (around 5), rises above 6.0 after two soap washes, indicating a weakened antimicrobial barrier.

Hygiene is of course essential, but to preserve the skin barrier, we recommend choosing mild cleansers with a physiological pH and applying a moisturizing cream after each wash to restore the skin’s hydrolipid film. Additionally, limit yourself to no more than one shower per day.

False.

Excessive exfoliation can significantly impair the skin barrier. By frequently removing dead cells from the stratum corneum, its integrity is compromised, making the skin more susceptible to irritants, pathogens, and dehydration. Several studies suggest that overly frequent or aggressive exfoliations contribute to the increase in barrier function alterations observed in industrialized societies. After an exfoliation, the skin barrier is weakened: this is why it is recommended to apply a moisturizing treatment afterward.

On the other hand, exfoliation should not be excluded from one's skincare routine. Gentle and controlled exfoliation helps remove excess keratinized cells that may disrupt the cohesion of the stratum corneum and enhance the absorption of topical treatments. Indeed, this process, naturally regulated by enzymes like kallikreins that break down corneodesmosomes to facilitate desquamation, decreases with age, highlighting the importance of supporting it. However, ensure you use a chemical or physical exfoliant suitable for your skin type (no AHAs for sensitive skin, no mechanical scrubs with large grains for damaged skin...).

One to two exfoliations per week are sufficient to support skin regeneration without compromising the skin's barrier function.

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