Different barriers contribute daily to protect man from the external environment: the skin, the respiratory system, and the intestine. Among these, the skin turns out to be the first protection against external agents of a chemical, physical or biological nature while simultaneously allowing its organization to avoid excessive water evaporation: a fundamental element for the physiology of our cells.
The skin barrier is constantly evolving in the newborn and up to about the first year of life. The stratum corneum is, in fact, 30% thinner than that of adults, there is a greater TEWL, and the skin barrier is not fully developed, thus exposing it to a greater risk of percutaneous absorption of irritating or harmful substances. These changes rapidity and continuous evolution lead to greater skin sensitivity during newborn and infant age. There is, therefore, the need to pay even more attention to everything applied to the skin, especially in the face of skin pathology.
The Barrier Function Of The Skin
The barrier function of the skin is due to the presence of several structures, including the stratum corneum, tight junctions, the microbiome, and the immune barrier. To allow the skin to perform its protective role efficiently, these structures must act in unison. The crucial role of the stratum corneum and, in particular, of the lipid matrix composed of ceramides, cholesterol, and fatty acids is now widely recognized: a deficiency or an imbalance in the relationship between these lipids determines the skin barrier.
In fact, in addition to the immunological and environmental factors, at the basis of this pathology, there is a genetic defect in the permeability of the skin barrier due to a lack of ceramides which leads to unbalancing the relationship between the components that form the lipid barrier, essential for guaranteeing the barrier function.
The Barrier Damage
On the one hand, the greater permeability of the barrier favors the penetration of external agents, fueling inflammation. Conversely, it determines increased transdermal water loss, favoring skin dryness and discomfort. Thus a vicious circle is established in which the facilitated entry of external agents feeds the inflammatory process, which in turn causes defensive reactions, including the thickening of the corneocytes layer, thus worsening the barrier function. Atopic dermatitis affects about 20% of children; in 15% of cases, it occurs within the first year of life (around 3 months). In 40% of cases, it persists even in adulthood.
Treatments To Restore The Epidermal Barrier
It’s essential to take care of it immediately with a complete and correct approach to act on inflammation and alteration of the skin barrier. The treatment, by the European guidelines, depends on the severity of atopic dermatitis, classified according to the SCORAD index:
- severe (SCORAD>50),
- moderate (SCORAD 25-50),
- mild (SCORAD <25).
Pharmacological treatment differs according to the severity of dermatitis. In all three degrees, however, from the lightest to the most severe, applying emollient cosmetics and medical devices is recommended for adults and children: the so-called “basic therapy,” in which the choice of emollient is strategic for the success of the treatment. To be effective, emollients must perform a superficial moisturizing activity and promote repairing and rebalancing the altered skin barrier.
To perform this function, they should contain ceramides, cholesterol, and fatty acids in the right proportions. It is also important to pay close attention to cleansing, which needs to be considered. This, even before the topical treatment, represents the first gesture in order not to damage the already compromised skin barrier further. In this sense, it is necessary to prefer affinity detergents, i.e., detergents that base their washing action on lipid molecules, which allow dirt to be removed much more delicately than foaming detergents (cleansing by contrast).
The Role Of The Barrier In Psoriasis
However, atopic dermatitis is not the only pathology in which barrier alteration is involved in the etiology of the disease. Another pathology for which epidermal lipids’ role in the barrier function has been thoroughly investigated in recent years is psoriasis. This pathology is determined by an unbalanced immunological response, which as a direct consequence, causes an altered keratinocyte proliferation cycle.
Although it occurs more frequently in adults, it is a pathology that can also arise in children: in a third of cases, it occurs in the first years of life. In children, particularly infants, the diagnosis is not easy, which is why childhood psoriasis is often underestimated. Recent studies have shown that the skin barrier of psoriatic subjects lacks epidermal lipids, particularly ceramides.
Consequently, this deficiency would allow greater penetration of external agents, which in turn lead to the uncontrolled activation of the already unbalanced reaction of the immune system, fueling the vicious circle at the base of psoriasis, in which genetic predisposition remains the fundamental factor.
Even in the case of psoriasis, therefore, the application of emollients containing epidermal lipids represents a fundamental aspect of therapy support. Recent studies have also demonstrated that the continuous application of these products helps reduce recurrences and maintain the results obtained with the therapy over time.
The Importance Of Emollients
Atopic dermatitis and psoriasis show us how the deficiency and imbalance in the ratios of epidermal lipids are triggering factors of the pathology together with genetic, immunological, and environmental factors. Alongside pharmacological therapy, applying lipid-based cosmetics and medical devices represents a fundamental aspect of treating these pathologies.
Furthermore, since the barrier is constitutionally altered and more exposed to allergens and external aggressions, it is important to pay attention to the formulation quality of emollient and cleansing products, choosing rigorous formulas free of potentially sensitizing or irritating ingredients, such as perfumes, some preservatives, lauryl sulfate surfactants, etc. Since the impaired permeability of the barrier is among the triggering factors, applying products containing epidermal lipids from an early age can help prevent or reduce the severity of these disorders.
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