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Keywords:

  • moisturization;
  • occlusivity;
  • scar;
  • striae

Synopsis

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

Scars are well known to have a stratum corneum (SC) that is malfunctional. Increases in transepidermal water loss and decreases in SC capacitance and conductance have been reported. Occlusion therapy is a well-known route to improving the signs and symptoms of scarring. Until recently that has been assumed to be totally pressure related. However, studies have demonstrated that the direct effects of hydration on keratinocytes and fibroblasts contribute to the reduction in hypertrophic scarring. Now it is well known that occlusion can regulate epidermal cytokine and growth factor production; changes in profibrotic and anti-fibrotic factors have been established. As a result, it is to be expected that moisturizers may improve the signs and symptoms of scars. As striae have been suggested to be anatomically similar to scars and as it is well established that paracrine signalling occurs in skin, it is expected that striae have similar SC issues. While one cannot exclude the effects of some of the ingredients used in the products, several studies are reported in this review that demonstrates that moisturization is a key component to reducing the clinical signs and symptoms of scars and striae. This is a good example of how knowledge of corneobiology leads to corneotherapies for these skin condition problems. The review is being written in memory of Professor Johann Wiechers who, before he died tragically in November 2011, performed two of the reported studies together with colleagues.

Résumé

Les cicatrices sont bien connues pour avoir une couche cornée dysfonctionnelle. L'augmentation de la perte insensible en eau et une diminution de la capacité de la couche cornée et de la conductance ont été signalées. La thérapie d'occlusion est une voie bien connue pour l'amélioration des signes et symptômes de la cicatrisation. Jusqu'à une date récente cela a été supposé être totalement lié à la pression. Cependant, des études ont démontré que les effets directs de l'hydratation sur les kératinocytes et des fibroblastes contribuent à la réduction de cicatrices hypertrophiques. Maintenant, il est bien connu que occlusion peut réguler la production de cytokines épidermiques et du facteur de croissance; des changements dans les facteurs profibrotiques et antifibrotiques ont été établis. En conséquence, il faut s'attendre à ce que les hydratants peuvent améliorer les signes et symptômes des cicatrices. Puisque les striae sont considérés être anatomiquement semblables à des cicatrices, et depuis qu'il est bien établi que la signalisation paracrine se produit dans la peau, on peut s'attendre à ce que les striae présentent des caractéristiques similaires au niveau de la couche cornée. Bien que l'on ne puisse pas exclure les effets de quelques-uns des ingrédients utilisés dans les produits, plusieurs études sont rapportés dans cette revue qui démontre que l'hydratation est une composante clé de la réduction des signes et des symptômes cliniques des cicatrices et vergetures. C'est un bon exemple de la façon dont la connaissance de corneobiology conduit à une corneotherapie pour ces problèmes de la peau. Ce document est présenté en souvenir du professeur Johann Wiechers qui, avant sa mort tragique en Novembre 2011, a effectué deux des études rapportées avec des collègues.


Background

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

Moisturizers have many effects on the skin. They can naturally hydrate the stratum corneum (SC) which will aid the desquamatory process in dry skin conditions but they will also smooth, soften and plump it [1, 2]. Through occlusive mechanisms, the epidermal expression of certain cytokines and growth factors [3-8] can be influenced, and the swelling effects on hydration will most likely influence signalling processes in the epidermis simply through changes in mechanical forces (stretching or compression) as all the cells are connected to each other via corneodesmosomes, desmosomes, tight junctions and gap junctions etc. [9]. Equally, as we now know there is more than one ‘occlusive’ mechanism that ingredients in moisturizers can work by either acting directly on the skin's surface or interacting with the SC lipids to induce hexagonal to orthorhombic phase transitions thereby making the intrinsic SC lipids less permeable [10]. Thus, the effects of moisturizers are complicated, they have more effects on the skin than simply hydrating it, they have pleotropic skin benefits and they are the ultimate vehicle of corneotherapy [11].

Several studies have now been reported that show the effects of moisturizers on reducing the signs and symptoms of scars and striae [12-16]. In addition to simple hydration, some of these studies report using a variety of ingredients such as onion extract, Centella Asiatica & Hyaluronic acid together with vitamin A palmitate and other antioxidants.

The purpose of this article is to set the scene on the changes in the SC in scars, and potentially striae, to discuss the impact of moisturization via occlusion on the scars and striae and to document the evidence of the effects of moisturizers on the signs and symptoms of scars and striae. It is being written in memory of Professor Johann Wiechers who, before he died tragically in November 2011, performed two of the reported studies together with colleagues.

Scars have changes in skin barrier properties

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

Scars are well known to have aberrations in SC functioning. Dramatic increases in transepidermal water loss (TEWL) and skin dryness have been observed, and changes in their biomechanical properties have been reported [17-19]. The changes in SC barrier function are especially evident in both atrophic and hypertrophic scars. Although striae have a different aetiology and different skin biomechanics [20], it is expected that they may possess similar SC characteristics as their development has been described as being similar to scar formation [21, 22]. As a result approaches that improve skin barrier properties are expected to improve the appearance of scars and striae. Indeed it has recently been quoted that ‘hydration of the scar surface is the basis of action of 90% of scar management systems on the market and that most oils, lotions and creams have beneficial effects on scars primarily on the basis of their hydrative capabilities' [23].

Evidence for occlusion improving the appearance of scars

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

Topical silicone gel sheets (SGS) or silicone gels and/or creams together with occlusive dressings have been proven to be an efficacious method for the treatment and prevention of hypertrophic scars. Any effects of pressure, temperature and chemistry of the SGS approach have been excluded in favour of the scar softening benefits of these treatments afforded by skin occlusion [24]. Nevertheless, as would be expected, the greater the occlusion, the greater the benefit [25, 26]. A 20% silicone oil-containing cream was approximately four times less effective compared to the same cream that had been applied but had also been covered with an occlusive dressing. Others came to the same conclusion, although they did point out that SGS is more effective than silicone ointment but was less convenient and suitable for exposed areas [27]. Further studies have also shown that the scar improvement benefits are not restricted to silicone; glycerine-based gel sheeting has also been shown to deliver comparable results to SGS [28]. Most recently it has been shown that an occlusive moisturizing cream applied with massage is just as effective as a self-drying silicone gel [29]. Thus, it would seem that occlusion is a procedure for improving the appearance of scars.

Mechanism of action of occlusion

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

The barrier properties of the skin are weakened in skin areas that are scarred [17]. Indeed as a scar heals its barrier properties improve [18]. These changes together with changes in the underlying skin structure leads also to the changes in the mechanical properties of scars. Naturally, occlusion will lead to an improvement in the barrier properties of the skin and improve SC softness and smoothness, but it has also been proposed that the restoration of barrier function could lead to a dampening of scar formation [3]. Studies conducted in vitro using keratinocytes and fibroblasts have come to the conclusion that the direct effects of hydration on keratinocytes and fibroblasts rather than the silicone itself were responsible for the reduction in the development of hypertrophic scarring [30]. Hydration itself can have a suppressive effect on collagen production in fibroblasts thereby reducing excessive scarring [4, 5]. In other studies, it has been demonstrated that the degree and duration of skin occlusion are important for reducing scar formation [6, 7]. Indeed it has been pointed out that ‘fibrosis is linked to the inflammatory state of the epidermis which is linked to the skin hydration state as a function of barrier function' [8]. In fact, it has been demonstrated that simple occlusion regulated epidermal cytokine production, increasing the ratio of anti-fibrotic/fibrotic cytokines to reduce hypertrophic scar formation [5]. Again, it would seem that occlusion is a useful approach for improving the appearance of scars.

Clinical evidence that topical products improve the appearance of scars and striae

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

It is now widely accepted that occlusion of the scar surface is the basis of action of scar management products [23]. Occlusion by hydration is one of the mechanisms thought to be acting in both silicone treatment and pressure therapy [31]. Also it has been reported that oils, creams and lotions have beneficial effects on this basis [22, 32].

For example, in a randomized controlled prospective study where patients were allocated to receive a hydrocolloid dressing or a moisturizer (Eucerin cream; Beiersdorf, Norwalk, CT, U.S.A) to keloids or hypertrophic scars, it was found that there was significantly reduced itching, somewhat reduced pain and increased skin pliability for both treatments over a period of 2 months [33]. The improvement in scar pliability increased in parallel for both the treatment groups. These authors came to the conclusion that hydration of the scar by the two treatments led to the symptomatic improvements in the scar cosmesis. Naturally, full occlusion with occlusive dressings will deliver a greater benefit than transient occlusion provided by typical occlusive agents such as petroleum jelly or other creams [25, 26]. This does not detract, however, from the fact that these topical agents have some effect on improving the appearance of scars. Others also report that petrolatum-based topical agents constitute a standard therapy in the management of postoperative wounds and are effective at improving scar cosmesis and symptomatology and is as equally as effective as an onion extract cream [34]. Equally, use of lanolin compared with petroleum jelly improved superficial wound recovery that can be related to lanolin's greater occlusivity properties [35, 36]. Moreover, in an investigator-blinded controlled study examining the effect of a cream containing an onion extract to improve the cosmetic appearance of postsurgical chest scars, it has been demonstrated that the cream improved scar softness, redness, texture and global skin appearance compared to no treatment over a period of 10 weeks with the effects being observed as early as 4 weeks [13]. However, the authors have not proven that it's the onion extract itself delivering the effects, it is highly likely that improvement in the scar appearance may be as a result of the total moisturizing effects of the product.

Although studied less in this context, it is to be expected that striae may respond similarly to scars following skin hydration. The Cochrane Collaboration has reviewed published data studying the prevention of the appearance of stretch marks during pregnancy and came to the conclusion that one of the creams in their analysis may have this capability [14]. That study was a vehicle-controlled trial for Trofolastin cream that indicated that some women, and especially those who developed stretch marks in puberty, may be able to avoid getting further marks in pregnancy [15]. It should be borne in mind that these trials were examining the effect of an active ingredient rather than just the effect of the occlusion from the whole product, that is, they were vehicle-controlled trials. However, 44% of women in the vehicle group did not develop striae, and for women without previous striae, their development was similar in both treatment groups indicating some benefit from the vehicle alone. Moreover, it has been demonstrated that in a randomized, controlled, investigator-blinded study studying striae on matched women's thighs that a cream containing an onion extract, Centella Asiatica & Hyaluronic acid produced improvements in the appearance and feel of striae compared to no treatment over a 12-week period [16]. Compared with no treatment, the product-treated thigh striae improved overall in appearance, colour, softness and texture and were statistically significantly different after 8 weeks of treatment. There was a 100% response in overall appearance, colour and texture and a 58% response in striae softness. This may be owing to the ingredients themselves but is highly likely to also be a result of the moisturization and occlusion effects of the products. However, these are cosmetic improvements to the appearance of the striae, and the treatment does not eliminate the striae or reduce their size. A vitamin A palmitate and antioxidant oil-based moisturizer was also similarly shown to improve the signs and symptoms of striae (Table 1) [12]. The study was not designed to understand specifically the effects of the vitamin A palmitate and antioxidants but the effect of the whole formulation on striae skin condition. Its occlusive properties have been demonstrated in vitro using the water vapour transmission rate (WVTR) test (untreated vs. treated membrane: 31.48 ± 3.06 vs. 23.53 ± 1.66; P < 0.05) and in vivo (baseline vs. immediate application: 21.28 ± 6.47 vs. 15.90 ± 3.70, P < 0.05). These translated into improvements in skin moisturization measured using the Corneometer but because of the known electrical insulation properties of oils with this instrument, the increases in skin hydration were only observed 2 h after application (baseline vs. 2 h 31.69 ± 6.30 vs. 35.65 ± 6.37, P < 0.05). These results clearly show an improvement in skin moisturization via occlusion from the anhydrous oil which may be contributing to the effects on the signs and symptoms of the striae.

Table 1. Product composition
Mineral Oil, Triisononanoin, Cetearyl ethylhexanoate, isopropyl myristate, Bisabolol, Tocopherol acetate, Retinyl palmitate, Calendula oil, Rosemary oil, Chamomile oil, BHT, Perfume.

Two other studies, one on scars and one on striae, were conducted recently to examine the effect of the vitamin A palmitate and antioxidant oil-based moisturizer tested previously (Table 1) [12]. The skin problems presented on the subjects' thigh, abdomen and hips in the striae study whereas they were on the leg, arm, back, abdomen, knee, trunk, hip and shoulder in the scar study. Matching scars or striae were large enough to allow half-scar or half-striae treatment allowing a paired study design with intra-individual comparisons compared to a comparator oil (results not published) (n = 38 for the striae study and n = 36 for the scar study). In the scar study Caucasian (82%), Negroid (10%) and Latino subjects (8%) were included with scars that were <1 year old, 1–2 years old and 2–3 years old. Caucasians (85%), Negroid (5%) and Latino (10%) were included in the striae study. The vast majority of striae were from postpregnancy, but 15% of the population had striae in the Caucasian group obtained from increased weight gain, whereas 50% of the Latino group had striae from adolescent growth spurts. Measurement of the aesthetic outcome was taken at baseline and at weeks 2, 4 and 8 of the study with the topical last application being 10–16 h before skin assessments were made, and subjects had not washed their skin within the last 2 h.

The primary assessment method for the assessment of both scars and striae was the Patient and Observer Scar Assessment Scale (POSAS) as this is the most comprehensive and quantitative grading assessment [37]. POSAS consists of a series of 12 questions each on a 10-point scale that are answered by the patient (PSAS; six questions) or the objective evaluator (OSAS; six questions) and the combination provides the POSAS score. In the scoring system, 1 represents normal skin and 10 being the worst imaginable scar or sensation. Thus, for either the patient or the observer scoring systems, 6 reflects normal skin and 60 is the worst skin condition. OSAS parameters are vascularity, pigmentation, pliability, thickness, relief and surface area. PSAS parameters include colour, pliability, thickness, relief, pain and itching. As there was no pain or itching associated with the striae or scars in these studies, PSAS score was generated from a 4-parameter scale. To help distinguish between vascularity and pigmentation, Plexiglas was used. The vascularity was assessed by pressing the Plexiglas on the scars or striae and surrounding skin while releasing it looking at capillary refill and the redness of the skin was assessed. To assess pigmentation, the scars or striae were blanched using the Plexiglas to eliminate the effects of vascularity, and the brownish colouration of the skin was assessed. Pliability was tested by wrinkling the scars and striae with the thumb and index finger. Thickness was the average distance between the subcutical-dermal border and the epidermal surface of the striae. Relief was the extent to which surface irregularities were present (compared with the adjacent normal skin) and surface area of the scars/striae was measured. Chromameter and assessments of digital photographs were also performed, but as there were no differences found, they are not reported here. All assessments were performed in an acclimatized room (21 ± 1°C and 50 ± 5% relative humidity).

Compared to baseline, the POSAS scores for vitamin A palmitate and antioxidant oil-based moisturizer were statistically significantly different to baseline at all time points (P < 0.001) in both studies. The mean values declined by almost 15 points (34.8% improvement) on the POSAS scale in the striae study and just over 9 points (26.2% improvement) in the scar trial from baseline to 8 weeks (Table 2).

Table 2. Absolute reductions in Patient and Observer Scar Assessment Scale (POSAS) scores and reductions relative to baseline in the scar and striae studies after treatment with the vitamin A palmitate and antioxidant-based moisturizer
DayMean vitamin A palmitate and antioxidant oil-based moisturizer POSAS scar valueDifference to baseline scar valueMean vitamin A palmitate and antioxidant oil-based moisturizer POSAS striae valueDifference to baseline striae value
135.2242.92
1532.00−3.1735.89−7.03
2929.51−5.9730.97−11.95
5726.00−9.2227.97−14.95

All values were significantly different to baseline using Wilcoxon Signed Rank Test (P < 0.001). In both studies, the vast majority of subjects improved in their appearance of scars and striae. In the striae study, 100% of subjects had an improvement in their POSAS score. In the scar study, approximately 92% of subjects had an improvement in their POSAS score. Also the magnitude of the changes was large (approximately 26% and 37% change from baseline). The separate OSAS and PSAS scores correlated with each other. As can be seen from Table 3, the only parameter that was not improved on the OSAS scale for the scar study at day 57 was vascularity. This parameter was, however, improved in the striae study. Pain and itch are not included in the PSAS scale as they were not present at baseline in either study.

Table 3. Reductions in OSAS and PSAS scores relative to baseline in the scar and striae studies after treatment with the vitamin A palmitate and antioxidant-based moisturizer
ParameterVitamin A palmitate and antioxidant oil-based moisturizer day 57 difference to baseline scar value (OSAS)Vitamin A palmitate and antioxidant oil-based moisturizer day 57 difference to baseline striae value (OSAS)ParameterVitamin A palmitate and antioxidant oil-based moisturizer day 57 difference to baseline scar value (PSAS)Vitamin A palmitate and antioxidant oil-based moisturizer day 57 difference to baseline striae value (PSAS)
  1. ns=not significant. P<0.05*, 0.01**, 0.001***.

Vascularity−0.028ns−0.553***Colour−1.583***−1.368***
Pigmentation−1.669***−2.158***Pliability−0.778*−0.553*
Pliability−1.444***−2.658***Thickness−1.083**−1.526***
Thickness−0.444**−1.211***Relief−1.194**−2.658***
Relief−0.694**−1.079***   
Surface−0.333*−0.579***   

In the scar study, the skin improvement was irrespective of the age of the scar (25.2–27.2% improvement depending on the age of the scar). Just comparing the POSAS scores between the <1 and 1–2 years scar age interval and the 1–2 and 2–3 years scar age interval gives a POSAS score of 6.18 points and 3.24 points, respectively. On average, use of the vitamin A palmitate and antioxidant-based moisturizer for only 2 months treatment improves the POSAS scores by 10 points for new scars, 9 points for 1–2 years old scars and 8 points for 2–3 years old scars (Table 4). This demonstrates a clear benefit of the moisturizing oil on the appearance of scars over and above just the simple passage of time on the scar cosmesis.

Table 4. Comparison of Patient and Observer Scar Assessment Scale (POSAS) scores at baseline for scars of different ages and improvements in their scores after treatment with the vitamin A palmitate and antioxidant-based moisturizer
Age of scar (years)Average POSAS score at baselineAverage improvement in POSAS per subject treated with the Vitamin A palmitate and antioxidant oil-based moisturiser
<1 year40.3310.17
1–2 years34.159.31
2–3 years30.918.09
All scars35.229.22

Figure 1 visualizes both the proportion of people and the extent of deterioration of the scar symptoms, improvement of scars or no effect after 8 weeks of the oil treatment. It is clear that the number of subjects who experienced scar deterioration is not only low (three subjects), but that the deterioration in POSAS score is also very small. The colours of the bars in Fig. 1 reflect the age of the scar studied. All colours are well spread throughout the graph, and there are no specific red, green or blue clusters. This is confirmed by the statistical analysis. Using the same linear regression model to investigate the effect of age of scar on the improvement in POSAS, the P-value was found to be 0.5533. This supports the fact that the oil helps to improve the appearance of scars and that this does not only apply to scars of a specific age.

image

Figure 1. All individual changes (improvements as well as deteriorations) in Patient and Observer Scar Assessment Scale scores after 57 days of use of a vitamin A palmitate and antioxidant oil-based moisturiser. Scars of <1 year of age = red, scars between 1 and 2 years of age = green and scars between 2 and 3 years of age = dark blue.

Download figure to PowerPoint

There was no statistically significant influence of the location of the scar, ethnic origin of the subjects or age of the scar using mixed model statistics. For the striae study, there was a difference for the location of the striae but the vast majority had striae only located on the abdomen. Nevertheless, the changes from baseline of the POSAS scores for the striae on the different body sites improved statistically at all time points for the abdomen (P < 0.001) and the thigh (P < 0.05) following topical application with the moisturizing oil. The striae on the hip were only proven to have a statistical trend of improvement because of the low numbers of striae present on this location of the body (n = 5; P = 0.06).

Nevertheless, these studies were not placebo-controlled studies, so we cannot exclude the effect of the vitamin A palmitate and/or other antioxidants present in the oil, but it does provide a clinically identifiable improvement in the signs and symptoms of scars and striae. It is expected that these ingredients will have some effect as they are known to have anti-ageing and depigmenting effects, but other oils have been shown to have similar effects (unpublished results). Moreover, the same oil has been shown to have an effect on the signs and symptoms of photodamaged skin on several body sites compared to a no treatment control group [38].

The studies outlined in this review provide evidence of an improvement in the cosmetic appearance of scars and striae by skin hydration as assessed by POSAS and other clinical grading scales.

Conclusion

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

Over the last few years, the effect of moisturizers on scars and striae has been documented. The improvement in the appearance of scars and striae is expected to be derived from the occlusive and hydrating properties of the moisturizers as well as the active ingredients they contain. However, there are few placebo-controlled trials to demonstrate the efficacy of the active ingredients. This is easier with an emulsion product but when a multi-component anhydrous oil is used, it is more difficult.

The mechanism of action of moisturization on the appearance of scars and striae is not surprising as now there are many studies documenting the occlusion effects of silicone gel films, glycerol gel films, silicone oil-containing creams and other moisturizers on improving scars and striae by this route. Hydration by occlusion has become an accepted mechanism of improving the appearance of scars in recent years as there are functional changes in the SC above scars (decreased hydration and impaired barrier function). We presume the same is true of striae, although we have no direct evidence, but anatomy studies support the view that striae are scars. Elias et al. [3] and later Mustoe et al. [8] have provided elegant hypotheses of the mechanisms by which occlusion exerts its benefits. An improvement in SC function leads to beneficial changes in cytokines and growth factors diminishing the symptoms of scars. We believe the same mechanisms will lead to appearance improvements in striae. Improvements in SC moisturization obviously leads to the improvements in skin condition, and the studies conducted on scars and striae reported here are a good example of how knowledge on scar (and possibly striae) corneobiology leads to corneotherapies for these skin condition problems [11].

Acknowledgements

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References

The studies on the vitamin A and antioxidant-containing moisturizer were conducted by proDerm, Germany and fully funded by Union Swiss. Professor AV Rawlings is a consultant to Union Swiss. This review was written in memory of Professor Johann Wiechers who passionately believed in the efficacy of moisturizers on all aspects of skin condition, but in this case was intimately involved in the clinical studies reported herein.

References

  1. Top of page
  2. SynopsisRésumé
  3. Background
  4. Scars have changes in skin barrier properties
  5. Evidence for occlusion improving the appearance of scars
  6. Mechanism of action of occlusion
  7. Clinical evidence that topical products improve the appearance of scars and striae
  8. Conclusion
  9. Acknowledgements
  10. References