Your skin barrier is a highly sophisticated protection that also assists in maintaining balance in body function. The skin barrier not only protects you from UV damage, infections, toxins and other assaults, it also keeps water in your body. A damaged skin barrier causes dryness, skin sensitivity, increases the risk of infection, local redness and inflammation. A less than healthy skin barrier does not look so great either!
An impaired skin barrier has varied presentations and is almost universally present in our clients. The conditions representing an impaired skin barrier include dermatitis, acne, eczema, psoriasis, rosacea, skin sensitivity, skin dryness and skin aging. The causes of disruption can be external, internal or both.
External factors leading to an impaired skin barrier.
- Too much cleansing or exfoliating depleting the skin of its natural lipid barrier and acid mantel.
- exposure to skincare products which have a too alkaline composition (not good for the acid mantel),
- chemicals in personal care products or cleaning products that can set up an inflammatory response
- environmental toxins (ditto)
- secondary to aesthetic procedures – peels, lasers, microdermabrasion where the procedure has been overzealous
- UV damage and exposure.
Internal factors leading to an impaired skin barrier.
- inflammation related to diet, gut dysbiosis, inflammatory gut disorder,
- genetic predisposition in the case of eczema, which has a defect in the production of ceramides essential for an intact lipid barrier,
- aging (loss of barrier function due to change in cholesterol content in the lipid barrier and impaired skin-tight junction),
- medications you take (e.g. cholesterol-lowering tablets can interfere with lipid barrier),
- genetic susceptibility (more common in lighter skin types, as the skin of colour has slightly more acid skin which is associated with a stronger skin barrier)
What makes up your skin barrier?
Your skin barrier is not one thing but consists of several elements: physical, chemical, immune and includes our resident skin microbiome. To consider what makes your skin barrier, it is best to look at the functions it plays.
Preventing water loss and the super lipid barrier!
One of the essential functions of our skin is preventing water loss. It may seem simplistic, but this is integral to our survival, and why, when this is damaged, our skin appears dry. This waterproofing is provided by the super lipid barrier of the stratum corneum. The outmost layers of skin cells are enveloped in multiple layers of lipids (fats), preventing water loss (because the fat will not allow water to pass through). This lipid barrier is created by epidermal cells called keratinocytes.
This lipid barrier consists of 3 key fats or lipids– cholesterol, ceramides, and free fatty acids, forming an intact barrier. For normal barrier function, there must be equal numbers of each molecule, forming a 1:1:1 ratio. Remember this ratio 1:1:1 as it is not only essential for barrier function but also repair. When the skin barrier is disrupted, repair only occurs when the lipids in the skincare product are presented in a 1:1:1 ratio.
This lipid barrier not only prevents water loss (trans-epidermal water loss or T.E.W.L), it is also essential in preventing harmful bacteria and toxins entering, helps in UV protections and also in keeping our resident skin microbes happy!
The key player in the skin moisture barrier is the outer layer of skin called the stratum corneum. Multiple layers of fatty (lipid) membranes surround multiple layers of ‘mature’ skin cells.
The skin has tight junctions as well as the gut.
In addition to the lipid barrier, a second tight junction skin barrier was discovered not long ago. Lying in the second most outer layer of your skin (stratum granulosum) is similar to the tight barriers found in our gut lining. Tight junction form the main barrier in the gut lining (disruption of this causes a leaky gut). Like the tight junction in the gut, it is controlled by proteins that act like lock, latch and spring to control the flow of what gets into our bodies selectively. Less is known about the purpose of the skin-tight junction barrier. However, recently, it has been understood that we can also have ‘leaky skin’ when the tight junctions are disturbed, things that shouldn’t enter the body via the skin do!. And this may play a role in developing food allergies.
The barrier to infection and entry of bad bacteria and other bugs. There are several components at play to protect against bad bugs from entering and causing infection.
The acid mantel – ‘it makes our skin sour.’
The acid mantel is not a physical layer on the skin. It is instead an acid gradient – as you get closer to the skin’s surface, it gets more acidic (or sour). (At the skin surface, the ph is about 5, whereas, inside the body, it is more neutral -7.4)
This plays an important role in keeping out bad bugs – like Stapholoccal aureus, which do not like acid environments and encouraging the friendly skin bugs that thrive in its sourness. The acids creating the acid mantel are produced as the lipid barrier is formed. When the acid mantel is disrupted, the skin barrier is disrupted – ( so be careful what products you put on your skin), and infection can occur.
Immune function of our skin.
Our skin’s innate and acquired immune function is very sophisticated as this is what stops any bad bugs invadeing to prevent them from causing infection.
- Antimicrobial peptides form part of the innate immune system – The epidermis cells’ cells form the super barrier and secret molecules that fight against bad bugs. (Antimicrobial peptides also occur in the gut)
These peptides are a defence response from our innate immune system. They recognise potentially harmful bugs, secret molecules which can kill them and activate other immune cells to come and eliminate them – this is true!
2. Immune cells – there is an interplay between immune cells in our skin. The Langerhans cells are specialised in the skin responsible for recognising anything invading, and they talk to our adaptive immune cells to get rid of the invader. Many other cells are involved in immune function, like mast cells, macrophages, t cells, all of which have a protective role.
3. Sebum produced in the oil glands also plays a role in antimicrobial protection. Secreted on the surface, mixed with the metabolites produced by the helpful bacteria that reside inside, this oily secretion’s acidity, is also believed to be defending against harmful bacteria.
The Skin Microbiome: the good bugs and the not so good.
We know a lot about the diversity of micro-organisms in our gut. Still, much less attention has focussed on the skin microbiome – until now, as with modern techniques revealing the true diversity of our skin’s normal flora. Most of these organisms do not live in the gut (as the skin has ph- 5 instead of the ph inside – 7.4, and they do not survive in acid environments).
Healthy skin – is all a matter of balance.
We know the normal skin microbiome helps protect us against colonising bugs that cause skin infections like impetigo or cellulitis. But normal skin bugs can contribute to skin problems when an overgrowth of a particular organism occurs. The resulting imbalance (dysbiosis) causes problems. (in acne, eczema, and even rosacea). Like the gut microbiome, healthy skin depends on the diversity and balance of the organisms.
The skin super lipid barrier and the anti-microbial barrier are closely related. If you disturb the skin barrier, you upset the microbiome and vice versa. Fixing the skin barrier allows the skin microbiome to come back into balance. This is because the (epidermal cells) keratinocytes (as well as producing the lipids for the super layer) also produce the antimicrobial peptides, determine the skin’s acidity that fosters the growth of good bacteria and inhibit the growth of bad ones. So when the keratinocytes deliver the lipids to waterproof the skin, they also deliver the anti-microbial peptides.
The sebum – a final layer of protection for the skin.
Though the lipids produced by the keratinocytes fill the spaces between cells of the stratum corneum barrier, they do not form the majority of fats on the skin. There is also a coating on all skin produced by the sebaceous glands secreted onto the surface and hair. The composition of sebaceous lipids are unique and consist of a mix of triglycerides, wax esters and squalene. Omega 3 and omega 6 fatty acids are essential for the formation of sebaceous lipids.
Sebum has an additional protective role; it provides a store of fatty acids that can be absorbed back into the epidermis to be used by keratinocytes for recycling into the lipid bilayer,
- it possesses antibacterial properties
- confer anti-oxidant protection through vitamin E.
- It also provides food for bacteria which are normally commensal.
- It provides additional protection against skin dehydration and repelling of water.
Repair the Skin Barrier – the first task in cosmetic medicine.
A damaged skin barrier allows increased trans-epidermal water loss (TEWL), resulting in dry skin interfering with the protective mechanisms- chemical, physical, acid mantel and antimicrobial defence mechanisms. The disrupted barrier allows allergens, microbes, and irritants to penetrate with resulting in inflammation.
In nature, when the skin barrier is damaged, the first task is restoring an intact epidermal barrier. We also consider restoring skin barrier as our first task in cosmetic medicine.
Signs and causes of impaired skin barrier include:
- Sensitive skin is perceived as various stinging, burning, irritation, or itching when using skincare products. Up to 60% of the normal population were found to have sensitive skin in a large study. This occurs in men and women and increases with age. https://pubmed.ncbi.nlm.nih.gov/30206954/ This highlights the importance of skincare formulation in protecting the skin barrier.
- All inflammatory skin conditions have, by definition, a disturbed barrier function—acne, psoriasis, rosacea and eczema.
- A damaged skin barrier is evident in aging skin. Over the age of 50, changes to skin barrier function occurred due to a decrease in cholesterol, changes to the skin-tight junction barrier and increased inflammation ‘inflammaging”. This inflammation arises from a dual source, the gut and the skin microbiome action on your immune cells.
- Blonde hair and red hair predisposes to more sensitive skin. The melanin in “skin of colour” confers a slightly more acid property to the skin surface, resulting in stronger barrier function.
- Impaired barriers occur at times of psychological stress or physical stress, as witnessed by stress precipitated outbreaks of acne, eczema, rosacea, and psoriasis.
- The use of medications such as oral steroids impairs the skin barrier and takes cholesterol-lowering medications called statins.
trans-epidermal water loss or T.E.W.L
innate and acquired immune function
Omega 6 oils are essential for the production of ceramides.