Dry skin? How your simple skin cream helps.
In this article, I’ll take a closer look at the benefits and limitations of moisturizers. I pick this product group as a representative for various “cosmeceuticals”, which are applied to the skin as creams, lotions, masks or the like and are supposed to unfold their effect by penetrating into the skin. All products claim that they are good for dry skin. And some claim much more. Rightly so?
Skin creams should be used, in my opinion, to maintain skin moisture and prevent dry skin. Skin creams that work very well against dry skin are already available for surprisingly little money (“Nivea” for example). This requires neither a magic formula nor any “revolutionary” new active ingredients. A good moisturizer from the drugstore or pharmacy is usually enough to maintain good skin hydration, even for dry skin.
Anything beyond that, beautifully packaged in fancy glass and high-gloss cardboard, is usually too much of a good thing. Futuristic-sounding active ingredients, new and revolutionary, are supposed to give the impression that the “serum” for 70 euros and above can do more than the classic moisturizer. From the improvement of the skin’s appearance to the formation of new collagen tissue, to the elimination of wrinkles. “Anti Aging” just, without this buzzword comes today almost no cream.
But in the vast majority of cases, these are empty promises. One or the other cream will certainly succeed in superficially concealing fine lines and visually improving a coarse skin texture due to its swelling effect. And there are certainly a number of soothing active ingredient complexes that promise relief from various skin irritations. But any claim of a “rejuvenating” effect I leave with a big question mark. Even if active ingredients are used that are promising in themselves (such as hyaluronic acid). The superficial application sets narrow limits even for the best active ingredient. I will explain why in the following.
Little to be achieved on the surface
The main reason for my doubt is due to the superficial effect common to creams, lotions and similar moisturizing products. It extends only to the top layer of the skin, the so-called epidermis. And even there, the vast majority of creams only reach the uppermost cell rows of the so-called “horny layer”. The problem with this is that their cells can hardly be “rejuvenated” any more, because most of them are already dead. Even the most sophisticated active ingredient will achieve only marginal effects here. To be more effective, it must penetrate into deeper skin layers. Into the deepest layers of the epidermis or, even better, into the dermis, where the blood vessels run and the metabolic processes central to aging take place.
But this is not so easy for creams, lotions, serums and the like. That’s why, in my practice in Munich, I rely on techniques such as microneedling, with which active ingredients can actually be introduced into the deep layers of the skin through microfine channels. Microneedling is an ideal procedure for stimulating collagen synthesis in the dermis and supporting it with specifically administered anti-aging active ingredients. But as you can already see at this point, dear reader, in order to be able to assess the effectiveness of moisturizer products, a certain knowledge of the structure of human skin is a prerequisite. Especially the outermost layer, the epidermis.
Therefore, my further considerations will first be preceded by a brief introduction to the “layer model” of human skin. In addition, I will discuss some elementary dermal metabolic processes which are important for the constant regeneration of the skin and its adequate moisturization. Why dry skin develops in the first place and what you can do about it will then immediately become clear.
Anatomy of the human skin
The human skin is basically composed of three layers (from the outside to the inside):
- the epidermis (“upper skin”)
- the dermis (“leather skin”)
- the subcutis (“lower skin”)
The epidermis and dermis together are often called the “cutis”. The cutis is between 1.5 and 4 mm thick, depending on the region of the body. The epidermis is relatively thin, measuring just 0.1 mm. The dermis measures between about 1.5 and 4mm. The hypodermis can be a few millimeters to several centimeters thick, depending on the amount of stored subcutaneous adipose tissue. The thickness of the skin also varies depending on gender and age.
The top layer of skin is the epidermis. It consists of several layers of a specific type of skin cell, the so-called keratinocytes. The epidermis renews itself continuously: new keratinocytes are formed in the lowest layers of the epidermis (basal layer, stratum basale) and then migrate to the skin surface (horny layer, stratum corneum). The individual layers of the epidermis are thus nothing more than different developmental states of one and the same cell type in the course of its migration or maturation.
Once at the surface, the keratinocytes transform into corneocytes (horny cells). As such, they form the outermost boundary of the skin before finally being shed as dead tissue. The complete cycle takes 2-4 weeks, during which the keratinocytes migrate from the deep basal layer to the uppermost layers of the horny layer. The epidermis, as the top layer of the skin, is thus a constantly renewing protective wall, whose building blocks are formed in the deepest layer, then undergo a process of differentiation and maturation on their way to the surface, to finally serve as part of the protective horny layer, to die off and be replaced by the next generation of cells. As mentioned, this happens all the time. Without interruption, each person loses up to 40,000 dead horn cells – per minute!
Between the basal layer and the horny layer, the epidermis has two other cell layers:
- In the spiny layer (stratum spinosum), which adjoins the basal layer, various cellular building blocks are provided to cause the horny cells to mature and to bind the finished horny cells together by means of “lipid cement” to form a resistant barrier.
- In the subsequent granular layer (stratum granulosum), the conversion of the still living keratinocyte to a dead horn cell takes place. In this process, the cell walls are strengthened and stiffened, the cells are further “cemented” together, and the cells are finally induced to suicide by dissolution of the nucleus and cell organelles. As solid cell bodies, thickly bound together by lipids, the dead keratinocytes form the outermost protective layer of the skin until, as mentioned, they are rejected and replaced by subsequent generations of cells.
What does this mean for our moisturizers? Skin creams and all types of cosmetics acting through the skin must first pass through this outermost protective layer of human skin, the stratum corneum. This is not particularly thick, only 5-10 micrometers, and also has only 10-20 individual cell layers. Nevertheless, this layer proves to be quite an effective barrier. Whether active ingredients can successfully penetrate the skin therefore depends, among other things, on their molecular size, the so-called “molecular weight”. It is measured in “Daltons”. As a rule of thumb, active ingredient molecules may only be a maximum of 500 Daltons in size in order to penetrate deeper through the skin barrier into the epidermis. However, the molecules of active ingredients that are important for skin moisturization and anti-aging are many times larger.
Hyaluronic acid, for example, occurs in various molecular weights starting at around 1 million Daltons, with more complex variants going up to several million Daltons. When cosmetics manufacturers advertise significantly lower molecular weights of 1000 Daltons and below, it is because they are not using hyaluronic acid itself, but a derivative. By way of comparison, BOTOX, on the other hand, has a molecular weight of around 900,000 Daltons. This is also far above any possibility of penetrating deeper into the skin. A “BOTOX cream”, as it is now and then circulating through the media and relevant internet forums, will therefore remain wishful thinking for the foreseeable future.
Another example is nicotine: The plant alkaloid has a very low molecular weight of only 162 Daltons and can therefore penetrate the skin barrier quite well. This is exploited in the well-known nicotine patches. The exact same principle also works with testosterone patches, since testosterone has a molecular weight of only 288 daltons.
Incidentally, the problem of hyaluron’s large molecules has been fuelling a whole separate track of biochemical research for some time now, which has set out to find new forms of delivery. Hyaluron drinks and supplements containing hyaluron have since seen the light of day, based on the assumption that “swallowed” hyaluron also leads to comparable anti-aging results as injected hyaluron. What all these products have in common, however, is that the results they promise cannot be clearly proven by studies. Especially since hyaluron, which is chemically similar to “dietary fiber”, is aggravated by the fact that it can only be digested by the body with difficulty.
But the functioning of the skin barrier is not only important in the direction from the outside to the inside. For the maintenance of skin hydration, the barrier from the inside to the outside counts in particular.
Why is “from the inside out” important?
The barrier function of the horny layer from the inside out is particularly important for maintaining sufficient skin moisture, because a central task of the horny layer is to regulate the cutaneous water balance. The horny layer forms a kind of natural “vapor barrier” that prevents the human body from evaporating water too quickly through the skin surface and drying out as a result. In principle, the horny layer can be thought of as a thin film that lies on the skin and is almost impermeable to water and water-soluble substances. Its internal structure resembles a brick wall, in which large and thick corneocytes (they are in fact the thickest cells in the human body) are stacked in rows on top of each other and firmly bonded with a “mortar” of epidermal lipids.
Various metabolic processes take place in the stratum corneum, the end products of which perform different tasks in the “protective wall”, some of which are chemical in nature and primarily directed against external influences (bacteria, fungi), and some of which are hydrophilic in nature to regulate the moisture balance.
Natural Moisturizing Factor and Lipid Mortar
In the upper area of the stratum corneum, amino acids are formed which act as a natural moisturizing factor (“NMF” for short) and are essential for the water-binding capacity of the outer horny layer. Together with the “kit” of epidermal lipids that binds the horny cells, NMF is the most important factor in maintaining skin moisture. And thus the suppleness and flexibility of the skin, as well as a fine skin texture and a rosy complexion. NMF deficiencies can occur due to disease (e.g. ichthyosis vulgaris), resulting in dehydration and scaling of the skin. Frequent washing with soap can also lead to a reduction of NMF and thus to dryness symptoms of the skin. A whole range of dermatocosmetic therapies is available to counteract a damaged NMF and effectively increase skin hydration.
Furthermore, a loss of epidermal lipids leads to skin dryness. Certain cholesterol-lowering drugs, for example, are known to affect epidermal lipid content as a side effect. In addition, frequent cleansing with soaps or the incorrect use of liquid oils (olive oil) in skin care also lead to washouts of skin lipids and thus to a disruption of the barrier function of the stratum corneum. And thus to dry skin and all subsequent symptoms, dermatologically as well as visually.
The healthy horny layer has a moisture content of about 10-20%. If the skin moisture content falls below this value, the skin appears dry and flaky. If, on the other hand, the water content is far above 20%, swelling occurs and the skin looks as if it has been in the bathtub too long. This swelling (“maceration”) reduces the barrier function of the horny layer. The gaps between the bricks in our brick-and-mortar model widen. This effect is used by many cosmetics to enable active ingredients to penetrate the outer barrier and reach somewhat deeper skin layers. Cosmetically induced swelling is referred to as “occlusion”, and cream ingredients that can achieve this are called “occlusives”.
I will not dwell on the dermis for long in the context of this text. This may come as a surprise, since the dermis contains the collagen and elastin fibers that are so important for a youthful appearance of the skin and whose slowed regeneration is decisive for skin aging. This is one of the reasons why most of my other blog posts so far have revolved around processes in the dermis, such as microneedling and/or PRP. The dermis would also have to be the primary target of all the active ingredients touted by cosmetic companies as having rejuvenating effects. Collagen, elastin, various vitamin and amino acid complexes, hyaluron, etc… all these substances act primarily in the dermis.
Alone: Externally applied skin care products will have difficulty penetrating the dermis. The epidermis proves far too impregnable for that. Most of the active ingredients that make it into the skin from creams or lotions get stuck in the upper rows of the “brick wall” of corneocytes and epidermal lipids. A favorite standard phrase of mine, which you may have read on the blog or on Twitter, is: “Hyaluron that is supposed to work has to come out of a cannula. Because that’s the only way it gets into the dermis. Via minimally invasive techniques such as injections or microneedling.
So let’s keep in mind: “anti-aging” promises of commercially marketed creams, serums, lotions, etc. see their effectiveness limited by three limits:
- Whether the active ingredients contained in them can actually have the effect they promise is not always proven by clear scientific studies.
- Even if the effect of certain substances is proven, this does not mean that they reach the skin depths to which they need to reach in order to exert their effect.
- In the superficial skin layers where they reach, they will only be able to exert their effect to a very limited extent, since the cells there are predominantly already dead or have only a very short life span before they are rejected by the body as skin scales.
So why use moisturizers at all?
With everything that has been said so far, one could easily argue that healthy skin does not need moisturizers, moisturizers in general and all kinds of other “cosmeceuticals”. But this is not true as a general rule. On the one hand, there are areas of the skin that are particularly susceptible to dryness, especially at a mature age, such as the lips or the elbows. And on the other hand, in our modern society, we create an actual need for moisturizers ourselves. Through our meticulous and thorough washing and cleansing routines, supplemented by all kinds of other daily body hygiene measures.
These “cultural techniques” damage the protective barrier of the stratum corneum and thus lead to an increased loss of moisture from the skin and subsequently to skin dryness. Damage to the protective barrier can be exacerbated by other factors, such as harmful environmental influences, nicotine consumption, hormone problems, stress, etc. Good moisturizers counteract such barrier damage very effectively.
What are moisturizers made of?
Moisturizers and other moisturizers are mostly composed of the following ingredients:
- Occlusives: Occlusives are substances that coat the skin with a type of “vapor barrier” to reduce transdermal water loss. Occlusives are hydrophobic and often extend into the uppermost layers of the stratum corneum, where they support the barrier function of the intercellular lipids.[br]Vaseline is considered the most effective occlusive substance. In addition, silicones and silicone elastomers are also widely used occlusives. Furthermore, fatty acids such as lanolic acid, fatty alcohols such as lanolin alcohol or cetyl alcohol, mineral oils such as kerosene or squalene, phospholipids such as lecithin or vegetable waxes such as carnauba.[br]The difference in efficiency between petrolatum and other occlusives is enormous: while 5% petrolatum reduces transdermal moisture loss by more than 98%, lanolin and mineral oil-based occlusives are only 20-30%.[br]However, occlusives that are too potent can also be problematic. Particularly in body folds or in zones of increased moisture (axillae, genital area), there is a risk of skin moisture in the stratum corneum rising above 40%, leading to maceration, which increases the risk of bacterial infections and fungal diseases. To circumvent this problem, occlusives are mostly combined with humectants.
- Humectants: The role of humectants, as the name implies, is to absorb and buffer environmental fluid. “Ambient” here can mean the moisture on and at the surface of the skin, though it can also mean the moisture IN the skin. This can mean, especially in areas of low humidity, that the use of an inappropriate skin care product actually INCREASES moisture loss from the skin. For this reason, moisturizers are preferably combined with occlusives to avoid such an effect. Common moisturizers are hyaluronic acid, glycerin, gelatine, honey, panthenol, urea, alpha-hydroxy acids (e.g. lactic acid, glycolic acid) or sodium and ammonium lactate.
- Emollients: Emollients have the task of making the skin smoother and more supple. They are, so to speak, the “replacement mortar” with which lost lipids between the corneocytes in the stratum corneum are replenished. Accordingly, they consist of fats or oils, and often enough they are the same substances listed under 2. as humectants. All moisturizers owe their “creaminess” to the emollients, even if they do not otherwise contain any lipid components.emollients can have an astringent effect, such as dimethicone or cyclomethicone. The cosmetic products then mostly advertise with “reduced pores”, “against oily skin” and the like. Or they are explicitly “refatting” like e.g. isopropyl palmitate, decyl oleate, jojoba oil or castor oil. Emollients often also have an antipruritic effect, which is why they are regularly an important ingredient of ointments for the relief of certain skin diseases (e.g. neurodermatitis).
- Emulsifiers: Emulsifiers have the task of keeping the hydrophilic (water-soluble) and hydrophobic (water-insoluble) substances contained in numerous formulations in stable contact. A distinction is made between anionic, cationic, amphoteric and nonionic emulsifiers, which are chemically mostly surfactants. Newer substances in this group are, for example, coconut monoglyceride sulfate synthesized from coconut oil and glycerin. Alkyl polyglycoside, which consists of sugar and fatty alcohols, is considered to be a particularly skin-compatible, non-ionic surfactant of the younger generation.
- Preservatives: Since very many commercial moisturizer products contain a large amount of water, they are subject to an increased risk of bacterial contamination. Manufacturers counter this risk by adding appropriate preservatives.
- Fragrances and pigments: For better marketability, cosmetic products should smell good and look appealing. Otherwise, these product ingredients have no function.
- UV protection: One of the few arguments clearly in favor of a skin cream is its possibly included protection against UV radiation. A high sun protection factor actually makes your skin cream an “anti-wrinkle cream,” albeit in a different way than advertised. Natural sunlight is a major contributor to skin aging, and a high UV protection in your skin cream will save you from that. Therefore, if you have to choose a moisturizer and you don’t know which one, always go for the one with the higher SPF. Simple.
- Botanicals: Aloe vera fans is a well-known representative here. As a moisturizer, the southern plant is very popular in creams and lotions, although the study results on this are unfortunately not clear. The same applies to its skin-soothing effect as after sun.
- Anti Aging Active Ingredients: The list of popular “miracle cures” is long and getting longer. In fact, as a recent SPIEGEL cover story put it, one has the impression that the cosmetics industry is specifically researching biochemical complexes that look good on the packaging as the “latest philosopher’s stone”, with names that sound as complicated as possible. Many of these active ingredients may have a benefit, others may not. You will probably only find this out by trying them yourself. But as already mentioned above: Due to the peculiarities of the skin anatomy, long-term rejuvenating effects seem rather unlikely.
How do I choose the optimal moisturizer?
From what has been said so far, there are already numerous indications for the choice of the individually suitable skin cream. In addition, it should be said that products with a low water content should be given preference, especially in the cold season. Creams with a high water content can lead to unattractive frostbite of the skin. Ointments (water in oil emulsions) are therefore more suitable when it is cold outside and a longer stay outdoors is planned.
For the normal season, it is best to opt for products that suit your skin type (dry/oily). In any case, if you have oily skin and/or acne, you need a non-comedogenic product. However, you should also avoid creams with a high water content in all areas of the body that are at risk of maceration (armpits, intimate area, body folds). Due to the large number of cosmetic ingredients, you should also keep an eye on the risk of allergic reactions. And as already mentioned, if you have to choose between several creams, choose the one with the highest SPF. This will turn your moisturizer into a real “anti-aging” product.