Many research articles have been published since the turn of this century investigating the origin, composition, function and potential benefits of vernix caseosa. Not only does this research provide an understanding of the formation of perfect young skin, some of it can be translated into benefits for the cosmetic industry. The present review summarizes the current knowledge of vernix caseosa and discusses the underlying principles by which vernix caseosa operates; this can be applied in moisturizing and barrier-enhancing products, although the proteolipid biofilm itself cannot be used directly on the human body. The most important characteristic of vernix caseosa is its controlled degree of occlusivity—neither too much nor too little.
Vernix caseosa is the creamy white, viscous biofilm that surrounds a newborn’s body during birth (see Figure 1). The Latin words vernix caseosa mean varnish and cheese-like, respectively, and indeed, sometimes the whole body is covered in this whitish cream during delivery. The vernix caseosa is produced during the last trimester of gestation as a remnant of the original periderm. It provides a temporary skin barrier that is suitable for the aqueous environment in utero, with active transport mechanisms between the amniotic fluid and embryo by virtue of its microvilli situated at the top of its surface.
Periderm cells are replaced continuously until 21 weeks of gestation when they are completely shed and replaced by the stratum corneum (SC). The shed periderm cells are mixed with secretions from the sebaceous glands within the epithelial walls to form vernix caseosa.1 At the same time, the fetal lungs mature, which requires amniotic surfactant levels to increase. This in turn causes the vernix caseosa to detach from the fetal skin surface, contributing to the turbidity of the amniotic fluid at the end of pregnancy.2
While the exact function of vernix caseosa is still under debate, a multitude of different functions have been suggested, and in some cases identified. These can be divided into prenatal, during birth and postnatal functions. Prenatal functions include: waterproofing, since due to the low surface energy, vernix caseosa is highly unwettable;3 the facilitation of the skin formation in utero;1 and protection of the fetus from acute or sub-acute chorioamnionitis (an inflammation of the outer (chorion) and inner (amnion) fetal membranes due to a bacterial infection).4, 5 During delivery, vernix caseosa acts as a lubricant while postnatally, it exhibits antioxidant, skin cleansing,6 temperature-regulating7 and antibacterial properties.8
Other possible prenatal roles have been suggested, such as facilitating the colonization of skin with microorganisms after birth,3,9 but for the cosmetic formulator, the most interesting properties of vernix caseosa are its skin moisturizing and skin barrier-enhancing properties. While a previous column linked the presence of orthorhombic skin lipid packing with good skin hydration,10 this column steps further back to examine how young, healthy skin is created.
Vernix caseosa Composition: The ‘Inside’ Story
The typical composition of vernix caseosa is 10% lipid, 10% protein and 80% water. The water is mainly present within the keratinocytes as identified with cryo-scanning electron microscopy coupled with X-ray beam analysis.11 Although the protein content is not as well-characterized as its lipid constituents, a plethora of antimicrobial peptides have been recently identified.2, 5, 8, 9 Much more is known about the lipid composition of vernix caseosa. Recent analyses of the lipid constituents have been published12-15 and these results are compared in Table 1 with the typical composition of SC lipids and skin surface lipids, also previously published.12, 14, 15
Table 1 groups together typical skin barrier lipids (ceramides, cholesterol and free fatty acids) as well as those originating from the sebaceous glands. Comparing these groups, one can clearly see that the SC and sebaceous glands produce completely different lipids. However, the lipids found in vernix caseosa are a mixture of skin barrier and sebaceous lipids (also see Table 1). Scientists have used this profile as a way to establish the origin of vernix caseosa. Its high content of squalene and wax esters originally suggested that the lipids in vernix caseosa were derived mainly from fetal sebaceous glands. Stewart et al., for instance, demonstrated in the early 1980s that the lipids in vernix caseosa were most likely derived from the sebaceous gland via the fatty acid composition of wax esters in this biofilm.16 Later studies, however, demonstrated the presence of all major SC lipids in vernix caseosa.12
Hoeger et al.13 refined this picture and demonstrated that the composition pattern of the ceramides found in vernix caseosa mirrored that of mid-gestational fetal epidermis, therefore representing what they called a homologous substitute for the immature epidermal barrier in fetal skin. Combine this with the fact that the periderm, mentioned above, is shed as the fetal sebaceous unit is developing, and this composition is explained.
If all the usual SC lipids including ceramides, cholesterol and free fatty acids are present in vernix caseosa, does this mean that vernix caseosa also fulfills a barrier function for the unborn child? In order to address this question, two other issues must first be addressed. Apart from having ceramides, cholesterol and free fatty acids present, the ceramide profile (i.e., which ceramides are present) and the packing state of the lipids (i.e., how they are grouped) need to meet certain requirements.
Hoeger et al.13 and Rissmann et al.15 both describe the complete ceramide profile of vernix caseosa. Whereas the former states that the ceramide profile is identical to mid-gestational and immature SC of a developing fetus, the latter states that although the levels of ceramides present in mature SC and the vernix caseosa are very different, their profiles are very similar (see Figure 2). Most abundant is CER(AH) at 22.0 ± 6.6% (formerly known as Ceramide 7); followed by slightly lower levels of CER(NS) (Cer 2, 19.5 ± 5.9%); CER(AS/NH) (Cer 5/8, 17.3 ± 3.3%); and CER(EOS) (Cer 1, 14.8 ± 6.0%).
When it comes to studying the structural packing of the vernix caseosa lipids, the available literature is scarce. In 2000, Pickens et al. had already described the vernix caseosa as a mobile or fluid phase SC, suggesting hardly any barrier function at all.11 This was confirmed by the work of Rissmann et al.,15 who concluded—based on small angle X-ray diffraction work—that there was no well-defined, long-range ordering, such as the occurrence of lamellae stacks, visible in the vernix caseosa samples they studied. However, a small population of lipids formed a long-range ordering at room temperature that, in a later article from the same group, was shown to disappear at elevated temperatures; these changes were found to be reversible.17
Finally, Rissmann et al. describe, in a third article, that vernix caseosa lipids are able to form the long periodicity phase with similar spacing to the human SC.18 This phase has been shown by Bouwstra et al. to be essential for the barrier function of the SC.19 But the temperature required for the formation of the long periodicity phase is different for vernix caseosa than SC barrier lipids, which can be most likely attributed to the different fatty acid chain composition (especially the presence of branched fatty acid chains) and the resulting difference in physicochemical properties.18 From this, one can conclude that the barrier function of vernix caseosa in the womb is definitely different from and less pronounced than the SC, and possibly only functions via the waterproofing mechanism described by Youssef et al.4 However, once the baby is delivered, the barrier function of the vernix caseosa changes again, as will be discussed next.
Vernix caseosa Water-holding Capacity: The ‘Outside’ Story
Once a baby is delivered, vernix caseosa has two important external functions. First, it must regulate the newborn’s transepidermal water loss (TEWL) and second, it must maintain its body temperature. Most babies, however, are immediately cleaned after delivery—and rumor has it that midwives apply some of the vernix caseosa they remove to their own hands, rendering them soft and well-hydrated. This suggests good hydrating properties of vernix caseosa. As was demonstrated in a previous column, however, good skin hydration is not just a matter of sufficient water in the skin; hydration also relates to optimized barrier function.10
The SC of a newborn baby is still in the process of adapting to extra-uterine life20 and has therefore not yet matured. At certain body sites, this may manifest itself in excessive water loss, leading not only to a reduced enzymatic activity in the skin, but also a reduced body temperature. It must be mentioned here, however, that other investigators state that term newborns have a functionally superb epidermal barrier.21
Over the last decade, many investigators have studied the water-holding capacity of vernix caseosa.22-28 This bio-film indeed has a unique water-holding capability. Despite its high water content (about 80%), water is released slowly from vernix caseosa, which is comparable to the release of water from a water-in-oil emulsion, as shown in Figure 3. Here, the loss of water is measured as a function of time from vernix caseosa, a water-in-oil emulsiona and an oil-in-water emulsionb.
Vernix caseosa released water at roughly the same rate as the w/o emulsion. At the end of 3 hr, vernix caseosa and the water-in-oil emulsion lost 8.1% and 6.6% of their original water content, respectively.26 In contrast, the o/w emulsion released as much as 30% of its total water content within the first 30 min of the experiment and 81% by the end of the experiment.25
The water release rate depends on the thickness of the layer of vernix caseosa applied. Gunt showed that the percentage of water lost from vernix caseosa films decreases with an increase in film thickness.25 In addition, the water loss profile depends on the relative humidity of the external environment—at a higher relative humidity, more water is retained within vernix caseosa, yet the difference in water loss in the range of 82% to 98% relative humidity is dramatic, relative to the losses measured in the range of 35% to 82% relative humidity (see Figure 4).
Tansirikongkol et al. took this experiment one step further and measured sorption-desorption curves at different relative humidities. They assessed the equilibrium water content in native vernix caseosa and vernix corneocytes and compared this to the SC.27 The equilibrium water content for native vernix and vernix corneocytes decreased with decreasing water activity (desorption study) and increased with increasing water activity (sorption study). Native vernix caseosa released and absorbed water at a very low level at low relative humidities. Once the humidity reached approximately 90%, the sorption and desorption curves rose dramatically (see Figure 5a).
Similarly, the sorption and desorption of water in vernix caseosa corneocytes occurred in low levels at low humidities. However, compared to native vernix, isolated vernix corneocytes exhibited unusually high water sorption at the 75% relative humidity condition, resulting in a 5- to 7-fold increase over the water content at 64% relative humidity (see Figure 5b).27
When this data is compared with similar curves established for SC by Kasting and Barai,29 it can be seen that native vernix caseosa showed the most similar water sorption profile to the profile of human SC. This combination of graphs suggests that when the relative humidity is lowered, as happens during delivery, water is released from the vernix corneocytes into the vernix and therefore to the SC. In doing so, it ensures that the imperfect SC of the newborn baby will have sufficient water for all its enzymes to function properly, so that a proper barrier can be formed.
Barrier Formation and Wound Healing
Summarizing the discussion thus far, immediately after birth, vernix caseosa is involved in maintaining the water balance in the skin of a newborn and in that way, helps to maintain skin temperature as well as the right water activity in the skin for optimal skin barrier formation. This suggests that vernix caseosa could also have a skin repairing effect when applied to damaged skin (i.e., wounds, scars) as well as dry skin.
Wound treatment and management is an important aspect of curing hospital patients that either are admitted with existing wounds or who obtain new wounds from surgical procedures. The healing of open cutaneous wounds has been divided into three overlapping phases: inflammation, re-epithelization and wound contraction. A moist environment was found to be optimal for wound healing, particularly during the inflammatory and proliferative phases, whereas enhanced cell migration, which is part of the re-epithelization process, has also been facilitated by moist conditions.30 Occlusive dressings have therefore become increasingly popular since they enhance wound healing primarily by preventing wound desiccation and by creating this moist environment.
However, when comparing fully occlusive foils to semi-occlusive foils, Schunck et al.30 found that wounds treated with semi-occlusive foils reduced wound contraction but enhanced cell migration and re-epithelization without irritation. This finding matches the observations of Visscher et al., who found that wounds treated with semi-permeable membranes undergo a more rapid barrier recovery than either non-occluded wounds or wounds under complete occlusion. Coverings that produce intermediate levels of skin hydration during recovery produced the highest barrier repair rates.31
These results suggest that barrier repair is augmented because semi-permeable membranes provide an optimal water vapor gradient during the wound healing process. Unfortunately, the optimal water gradient for wound care was not investigated but studies in the SC have shown that there is a critical range of water activities of 80% to 95% relative humidity, which permits filaggrin proteolysis to take place.32
The ideal water vapor transport rate through vernix caseosa and its implications for barrier repair were presented by Gunt et al. in 2002.33 The flux of water was measured as a function of time through an artificial membranec that was chosen because it had a water vapor transport profile in the same range as that of preterm infant or wounded skin.
This data was combined with the SC barrier recovery following tape stripping assessed previously,31 and the resulting graph is shown in Figure 6. This shows that optimal barrier recovery is obtained when the water vapor transport rate is in the range of 25–65 g.m-2.h-1. In this experiment vernix caseosa has a water vapor transport rate of 25 g.m-2.h-1 and 70 g.m-2.h-1, depending on the thickness of the layer of vernix caseosa applied, avoiding both total occlusion of the skin surface and total free transport of water, where the barrier recovery rate is significantly lower.33
These findings make vernix caseosa a perfect candidate as a therapeutic to be applied topically to impaired and/or damaged human skin, but because it is a biological material of human origin, and because of its less favorable cosmetic properties—e.g., cheesy appearance, odor, consistency, potential presence of blood and skin cells—its use is not widespread. The scientific literature references a limited number of research papers where vernix caseosa has been tested on human skin. In one Russian study, for example, vernix caseosa exhibited wound healing properties in adults treated for trophic ulcers of the lower extremities.34 In another, Moraille et al.6 investigated the skin cleansing properties of vernix caseosa on the volar forearm of human subjects. A study by Bautista et al. measured baseline surface hydration, moisture accumulation and TEWL, concluding that vernix caseosa treated skin had a significantly higher water-holding capacity, which was provisionally attributed to the absorption of water by the fetal corneocytes;23 similar work was conducted by Gunt.25
A fifth study by Barai using vernix caseosa on human skin in vivo measured the speed of barrier repair of tape stripped volar forearm skin that showed an intermediate water vapor permeability, resulting in a rapid increase in barrier recovery between days 3 and 5, following tape stripping.35 Interestingly, the vernix caseosa samples were sterilized by gamma radiation after collection6, 23, 35 and before application to the skin of the newborn’s mother.35
The biological origin of vernix caseosa has led to two types of current research. First, it is being used in cultured skin substitutes that serve as wound healing models to study fundamental skin biology.36 In addition, synthetic analogues of vernix caseosa are being developed in an attempt to obtain its beneficial properties from a non-biological origin; after all, this is where great potential is, as Haubrich states: “Application of the fetal/neonatal skin science findings (of vernix caseosa) to the adult burn population offers the potential for a clinically relevant homologous substitute for impaired integrity.”37 Therefore, the last section of this review will evaluate current attempts to mimic vernix caseosa and identify the criteria for success, to give cosmetic formulators some guidance as to how to make a perfect skin repair cream.
How to Mimic Vernix caseosa
Understanding the physical chemistry and biology of vernix caseosa poses a significant challenge to the cosmetic scientist. Hoath et al.38 list the functions and characteristics that should be fulfilled by a synthetic analogue of vernix caseosa. These include considerations such as being: “structurally similar to the stratum corneum, which it intimately covers; vernix caseosa lacks lipid lamellae [although Rissmann et al. recently did find some18] and desmosomal contact. Uniquely human, vernix caseosa is multifunctional: a skin cleanser, moisturizer, anti-infective and antioxidant, which works in both aqueous and non-aqueous environments.
“In utero, its rheological properties are modified by extracutaneous secretions such as pulmonary surfactant. Detached vernix is swallowed by the fetus. Vernix contributes to the electrical isolation of the fetus and has osmoregulatory capability. At the time of birth, its water content precisely matches the cube of the golden section ratio. Following tactile spreading, polygonal vernix corneocytes orient parallel to the skin surface. The hydrophilic (intracorneocyte) and hydrophobic (external lipid) domains of vernix contain a plethora of biologically active, small molecules in a complex, structured array.
“Cleansing studies6 support ready entry of applied vernix into surface pores such as hair follicles. Vernix has a nongreasy feel and its physical properties hypothetically contribute to the panoply of sensory cues, which attract caregivers to the skin of the newborn. The possibility that vernix contains pheromones, like mother’s milk, is open to investigation. Vernix facilitates acid mantle formation and presumably contributes to optimal bacterial colonization of newborn skin after birth.” Imagine getting such a product brief from marketing!
From all of the above, it is clear that a synthetic analogue of vernix caseosa cannot simply mimic all its biological and physical characteristics. Formulators have therefore focused on a few main points, including the water-holding capacity and the water vapor transport rate; more recently, the skin barrier effect has become another focus. Papers describing synthetic analogues of vernix caseosa include the following, discussed in chronological order of publication:
Sumida 1998: Sumida et al.12 were (one of) the first to describe a pseudo vernix caseosa formulation and found that the skin’s hygroscopicity and water-holding ability markedly improved after application of a test cream, even after washing with water. The authors suggested that the liquid crystalline structure of both the vernix caseosa and pseudo vernix caseosa formulation contributed water-absorption ability to these lipid mixtures.
The next six publications describing synthetic analogues for vernix caseosa all come from the University of Cincinnati School of Pharmacy, or the Skin Science Institute at the Cincinnati Children’s Hospital Research Foundation, which clearly made this into a research theme for almost a decade. It started with a poster of Bautista et al.22 in which vernix caseosa was compared with a petrolatum and mineral oil-based ointmentd and petrolatum. Initially, the comparisons were only conducted with oil-based formulations but over the course of approximately seven years, more complex formulations were studied.
Bautista 1999: In the first poster from Bautista et al.,22 three test creams were applied to the volar skin surface of adult volunteers following cleansing; these contained vernix caseosa, a petrolatum- and mineral oil-based ointmentd and petrolatum. Results indicated an increase in skin surface hydration on the sites where barrier creams had been applied—but not on the vernix caseosa-treated control sites. The researchers concluded that there are major differences between vernix caseosa and the o/o ointments.
Youssef, Bautista 2000: Youssef et al.24 compared the in vitro tritiated water flux through layers of varying thickness of vernix caseosa, a petrolatum- and mineral oil-based ointmentd and petrolatum, and found that the permeability coefficient of water through a film of vernix caseosa with a thickness of 20 μm was significantly higher than that through both the petrolatum and mineral oil ointment (2-fold) and petrolatum alone (25-fold). This supported the hypothesis that vernix caseosa does not act as a totally occlusive biofilm in utero but rather forms a semi-occlusive barrier overlaying the developing SC.
Also in 2000, Bautista et al.23 published the first full paper on the comparison between vernix caseosa and standard oil-based ointments, of which the conclusions were, as might be expected, similar to the 1999 poster. In this paper, a petrolatum-, mineral oil- and lanolin alcohol-based w/o emulsione also was included. Given the lipid constituents of vernix caseosa, the researchers anticipated that it would function as a hydrophobic barrier to prevent water loss and thereby act in a similar manner to hydrophobic ointments.
Surface electrical capacitance and TEWL experiments were conducted as indices of surface hydration. Sorption-desorption profiles were taken to determine skin surface hydrophobicity and immediately after the application of vernix caseosa, an increase in the rate of water loss from the skin surface was noted. Relative to control skin and the skin treated with the ointments and w/o emulsions, the application of vernix caseosa to freshly bathed human skin resulted in a unique profile of temporal change in baseline surface hydration, moisture accumulation and water-holding capacity (see Figure 7). These results, however, indicated major differences between human vernix caseosa, standard ointments and w/o emulsions, especially in their time profiles.23
Gunt 2002: The next publication was a thesis from Gunt.25 Apart from studying fundamentals such as the influence of film thickness and relative humidity (see Figure 4), Gunt was the first to measure the water loss profiles of: vernix caseosa; the w/o emulsiona; o/w emulsionb (see Figure 3); and cubosomes. Cubosomes, or cubic liquid crystalline nanoparticles, have a bicontinuous liquid phase structure wherein both the water and lipid domains are continuous.
The lipid bilayer forms the building block of the bicontinuous cubic phase and is arranged in periodic three-dimensional structures.39 Glycerol mono-olein-water, for instance, exhibits a bicontinuous cubic phase. These systems are highly viscous, clear, and have a high surface area.
Gunt’s in vivo findings suggested that cubosome formulations did not impede water loss and the rate of moisture accumulation for cubosome formulas was higher than that of petrolatum or petrolatum-, mineral oil- and lanolin alcohol-based w/o emulsionsd, suggesting that more moisture was built up with cubosome formulas than occlusive petrolatum and petrolatum-based products.
Both the vernix caseosa and cubosome formulations, which showed increased hydration at raised ambient humidity in vitro, also showed a higher water-holding capacity in vivo. From the water vapor transport data, Gunt concluded that the lipid fraction of vernix caseosa is primarily responsible for providing a controlled water vapor transport, whereas the role of cellular components of vernix caseosa is still unclear.
Since the increase in hydration at raised humidity is due to the entire vernix caseosa composition, however, one cannot exclude vernix caseosa cells from the material. These studies supported the view that topical application of vernix caseosa may provide the optimum water gradient required for restoration and development of the stratum corneum barrier by allowing the generation of NMF; the cubosomes were able to provide this both in vitro and in vivo.
Barai 2006: While the work of Gunt in 2002 identified that cubosomes were the best synthetic analogues of vernix caseosa so far, Barai assessed the effects of vernix caseosa and synthetic analogues on barrier repair in 2006.35 These results, described above, identified that the semi-permeability or semi-occlusivity of vernix caseosa was an essential requirement for its biological benefits, since the effect of the petrolatum- and mineral oil-based ointmentd and other barrier creams were too occlusive.
Tansirikongkol 2006-07: The last work on vernix caseosa synthetic analogues from the University of Cincinnati was conducted by Tansirikongkol14, 26 and focused on high internal phase emulsions—i.e., w/o emulsions with an internal aqueous phase, as high as 78% (see Figure 8). This work aimed to simulate the water/lipid ratio and water-handling properties of native vernix caseosa by combining the slow water release profile of w/o emulsions with the high water content of o/w-emulsions. Initially the oil phase contained conventional, non-vernix caseosa-like lipids but later, more vernix caseosa-like lipids were used.
Preparations with vernix caseosa-like lipids demonstrated water release profiles closer to that of native vernix caseosa than those with conventional lipids. The remainder of Tansirikongkol’s work focused more on the protective function of vernix caseosa against the enzymes present in the amniotic fluid, such as the chymotryptic enzyme, and excrements21 than on the development of synthetic analogues of vernix caseosa.
Erdal and Araman, Bouwstra, Hennink 2007: The children’s hospital and university in Cincinnati were not the only groups working on vernix caseosa imitations. Erdal and Araman from Istanbul University, for instance, suggested to be working on the same but results were not provided.40 As indicated above, Gunt had already identified that the total composition was important, not just the vernix caseosa lipids.25 However, it was when Bouwstra, PhD, of the University of Leiden, Netherlands, and Hennink, PhD, of the University of Utrecht, Netherlands, began to collaborate that a fundamentally different approach to vernix caseosa imitation emerged based on creating “cell-like” structures containing water in a lipid base formation rather than an o/w or w/o emulsion.
While Rissmann, PhD, worked with Bouwstra and Ponec, PhD, to characterize the lipids in vernix caseosa to study their packing and structure, Oudshoorn, PhD, worked with Hennink, on mimicking the vernix caseosa corneocytes. All literature cited until now has stated that water is present in the vernix caseosa corneocytes, and that vernix caseosa is different in that it can take up water at high relative humidities, but apart from the cubosomes, no formulation was capable of mimicking this.
Methacrylated hyperbranched polyglycerol microparticles with uniform sizes and shapes were prepared using photolithography, resulting in a size range of 30 μm to 1,400 μm.41 For the synthetic variant of vernix caseosa corneocytes, hexagons with a diameter of 30 μm were prepared, similar to the size of human corneocytes, which were loaded with FITC-dextran and coated with lipids (see Figure 9). Next, a lipid mixture mimicking the intercellular lipid composition and organization of vernix caseosa was prepared—similar to that reported in Table 1 for vernix caseosa, from Rissmann et al.15—and mixed in different ratios with the microparticles. Subsequently, the water-handling properties were measured gravimetrically and compared to native vernix caseosa in a dehydration study over P2O5. The result of this experiment is shown in Figure 10.28
Vernix caseosa is characterized by an initial rapid water loss prior to a sustained, steady dehydration at room temperature. Of all the synthetic analogues developed, the one labeled B2c (see Figure 10) was closest to native vernix caseosa; this sample included coated particles and had an initial water content of 80%; the particle/lipid ratio was 2:1. With these modifications, the researchers were able to extend the water release from 24 hr to 140 hr.28 This of course raised the question of whether or not the synthetic vernix caseosa also had a superb barrier repair mechanism, which was the subject of later papers.
First, a tape-stripping model on mouse skin was developed in which skin was stripped to a specific level (79 ± 6 g/m2/hr), where a crust was formed and almost complete recovery (~90%) was obtained within only 8 days. The topical application of vernix caseosa considerably increased initial and long-term recovery, promoted a rapid formation of the SC, and prevented epidermal thickening.42
Second, this model was treated with the same synthetic biofilms as well as oil-based ointments and the skin barrier recovery was compared to native vernix caseosa. Application of all tested formulations improved the skin barrier recovery and reduced crust formation and hyperproliferation but remarkably, the best-performing biofilm was the one containing uncoated particles with 50% (w/w) initial water content and a particle/lipid ratio of 2:1. The fact that the water profile experiments depicted in Figure 10 were the most similar to vernix caseosa, in which the initial water content was 80%, indicated that the amount of lipids might play an important role in the skin barrier recovery.
This raised the question of how important water-handling properties, as well as the presence of corneocytes, are for barrier recovery. Synthetic lipid mixtures with and without barrier lipids were therefore included in the study. The skin barrier repair results for a water and particle-free formulation with barrier lipids were very similar to those observed for native vernix caseosa. This demonstrated that the lipids, including barrier lipids, play a more prominent role in barrier recovery than the water content and presence of corneocytes. The latter, however, may be beneficial for increasing skin hydration and act as a drug delivery reservoir.43
Vernix caseosa: The Ultimate Natural Cosmetic?
Scientific research of the last decade has provided sufficient evidence for the beneficial properties of vernix caseosa as a barrier cream that not only corrects moisturization levels within the skin, but also improves skin barrier recovery by creating and maintaining a water activity level that allows all enzymes to function properly. However, its availability is insufficient to address the needs of the world of products that can restore skin barrier function and moisturization. Synthetic analogues have therefore been created and tested, and such vernix caseosa substitutes must meet only one criterion to be successful. While the necessity of water in such a formulation is still debated (for instance, see Reference 43), the semi-permeable nature of the product is absolutely essential, since both fully occlusive and non-occlusive products function far less well; and indeed there are already a few cosmetic ingredients44 as well as formulated products on the market that meet this requirement.
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