The skin acts as an active immune organ, where microbiome, chemical, physical, and immune barriers form an interactive network. The skin is the outermost layer of the body with an extensive surface area and is the first line of defense against a multitude of external pathogens and environmental insults. The skin also has important homeostatic functions such as reducing water loss and contributing to thermoregulation of the body.
What is The Skin Barrier?
Known as the stratum corneum, the skin barrier is essentially the outermost layer of the skin and the first layer of the epidermis, made of hardened dead skin cells. It offers protection for the underlying layers of living, healthy cells. The dead cells shed in a process known as desquamation, and the cycle depends on your age, taking 28 to 45 days in your thirties, 45 to 60 days in your forties and 90 days in your fifties.
The stratum corneum is the first line of defense for the body, serving an essential role as a protective skin barrier against the external environment. The stratum corneum aids in hydration and water retention, which prevents cracking of the skin. The human stratum corneum comprises 15 layers of flattened corneocytes.
Skin Barrier Immunity
The epidermis mediates a broad set of protective ‘barrier’ functions that includes defense against pathogen challenges. Permeability and antimicrobial function are both co-regulated and interdependent, overlapping through the dual activities of their lipid/protein constituents. Most of the defensive (barrier) functions of the epidermis localize to the stratum corneum, which limits pathogen colonization through its low water content, acidic pH, resident normal microflora and surface-deposited antimicrobial lipids. These various barrier functions are largely mediated by either the corneocyte or the extracellular matrix and it is both the localization and the organization of secreted hydrophobic lipids into characteristic lamellar bilayers that is critical not only for permeability barrier function, but also for antimicrobial function through its contribution to the maintenance of the stratum corneum integrity. Low constitutive levels of antimicrobial peptides under basal conditions emphasize the key role of epithelial structure in antimicrobial defense. But antimicrobial peptide synthesis and delivery to the stratum corneum interstices accelerates after external insults to the barrier.
Causes of Skin Barrier Damage
Daily, your skin defends against a barrage of threats, many of which come from outside your body, and a few come from within. Some of the external and internal factors that can affect your skin barrier include too humid or too dry environment, allergens, irritants, pollutants, too much sun exposure, alkaline detergent, soaps, exposure to harsh chemicals, over-exfoliation or over-washing, steroid, psychological distress and genetic factors that may make you more prone to certain skin conditions like atopic dermatitis and psoriasis.
Signs of Damaged Skin Barrier
A damaged skin barrier can express itself in a variety of ways, but at the core of the issue is water loss. It often appears dry and flakey, it can be itchy or painful, and feel rough to the touch. Skin barrier damage may be evident just based on the way the skin looks and feels, including acne, dry, scaly skin, infection, inflammation, irritation, itchiness, rough patches, stinging, tenderness or sensitivity.
The Acid Mantle
The acid mantle is the thin film on the skin’s surface that helps act as a barrier against bacteria, viruses, and other contaminants. It also holds in moisture and liquid, retaining the skin’s hydration levels. The acid mantle is actually made up of sebum – that waxy, oily substance that is secreted by the sebaceous gland under the skin. When the acid mantle is mixed with amino acids from sweat, this creates our skin’s pH level. It helps protect skin from abrasions and cracks.
While an excess in sebum can lead to unwanted oiliness and clogged pores, sebum is essential to make up the acid mantle and therefore protect the skin. Harsh, soapy and foaming cleansers can be damaging to the acid mantle, as they strip away all oils of the skin – including the sebum that makes up the skin’s protective barrier. This leaves the skin susceptible to bacteria and environmental stressors.
The Relation between PH and Skin
PH (potential of hydrogen) is a chemistry term that refers to the acidity or basicity of something. A pH less than 7 is considered acidic, and higher than 7 is basic, or alkaline. Your skin’s pH is affected by your diet and environmental factors.
When the pH of the skin’s acid mantle is balanced, it is able to better protect itself. When unbalanced, however, the skin can be a breeding ground of bacteria, experience breakouts, be too oily, dry, sensitive, or red and wrinkle prematurely.
Your choice of skin care products, cleansing routines, exfoliation and moisturizing treatments are only one part of achieving healthy pH balanced skin. A proper diet can also greatly affect your skin’s health and help create the perfect pH balance that healthy skin requires.
Tips to Repair Skin Barrier
Use a gentle cleanser. Avoid using harsh soaps and detergents. Instead, opt for a gentle, fragrance-free cleanser to avoid irritating skin. Skincare products with ingredients like ceramide, glycerin, and hyaluronic acid all help replenish the skin’s natural moisture barrier to restore hydration.
Avoid long hot showers. Excess heat strips away valuable nutrients and natural oils that protect our skin and can set off a chain reaction leading to a damaged skin barrier.
Exfoliate gently. While exfoliation sessions can be beneficial, scrubbing skin too vigorously can damage it. The same goes for over-exfoliation; once or twice per week is usually more than enough to keep skin happy. Try using a softer exfoliating product or tool (like a loofah) to avoid irritating skin.
Wear sunscreen. Not only does regularly applying sunscreen help prevent skin cancer, it also protects our cells from damage caused by UV rays.
Drink plenty of water. Eat foods with omega-3 fatty acids. Incorporating foods that are rich in omega-3s fatty acids—like salmon, flaxseed, chia seeds, and walnuts—may reduce inflammation and maintain skin health.
Treat existing skin conditions. It’s essential to get proper care for underlying skin conditions, like atopic dermatitis, as these can worsen, lead to infection, or cause other complications if left untreated.