The effect of moisturisers on scars: a systematic review

Abstract

Introduction: Scars, including keloid and hypertrophic scars, are a common and unpleasant cosmetic and sometimes functional side effect of burn injury, trauma or surgery. Moisturising is one of the most common scar management techniques recommended by health professionals. Many clinicians believe that moisturiser application to scars can hydrate, reduce itch and increase pliability. Since trans-epidermal water loss (TEWL) is thought to be the mechanism of action behind the effectiveness of silicone gel sheeting/contact media, it may be that moisturisers also impact on TEWL to have an effect on scars. Some moisturisers also contain additional ingredients, such as vitamins or pharmaceuticals, which may also have an effect on scars. This systematic review aims to assess the effect of moisturisers on scars, excepting atrophic scars. The aim is to present recommendations that are relevant and useful to consumers and clinicians. Method: Databases searched were PubMed, CINAHL, Embase and Web of Science. Critical appraisal was conducted using Joanna Briggs Institute (JBI) tools. The search located 33 studies of low quality and high risk of bias and these were selected for inclusion: 14 RCTs, 11 quasi-experimental, seven case series and one case report. Overall there were 867 participants or scars included in the review. Data on the outcomes reported by the included studies was extracted using JBI tools. A subset of seven studies, including a total of 82 keloids, examining the outcome of recurrence of keloids post-excision and application of Imiquimod cream was subjected to a meta-analysis utilising StatsDirect software (Cambridge, UK) and the random effects model. In an attempt to determine if the location of the keloid or the excision method and resultant method of healing (primary closure versus healing by secondary intention) impacted these results, subgroup analysis was performed. Narrative synthesis was performed on the results of the remaining 26 included studies. The subjective nature of outcome/scar measurement was noteworthy. Despite the variable quality of the studies, all were included so as to provide a current view of the state of the evidence. Outcomes addressed in the narrative synthesis included cosmesis, scar parameters, itch and pain, TEWL and in vitro outcomes. Results: Thirteen moisturisers were examined for their effects on cosmesis. Moisturisers that were reported to have statistically significant positive effects on cosmesis included Lumiere Bio-Restorative Eye Cream, Tretinoin, Scarguard® and Cetaphil®. Imiquimod was the only moisturiser found to have a statistically significant detrimental effect on cosmesis. Studies examining 18 different moisturisers reported on scar parameters. Of these, those that reported a statistically significant effect on scar parameters were Imiquimod, Aquaphor®, Mederma®, Scarguard® HSE (hydrocortisone, silicone, vitamin E), Cetaphil®, Tretinoin, Eucerin®, Putrescine, Keratin Gel and Doxepin. Eight moisturisers were examined for their effects on itch and pain; statistically significant benefits on both outcomes were observed with Doxepin, Provase®, Mugwort lotion and Eucerin®. Only one study examined TEWL as an outcome measure and found Alhydran to have a statistically significant positive effect. Considering in vitro outcomes, only one moisturiser, Dermovate, did not have a statistically significant effect, whereas the others, Tretinoin, Wubeizi ointment and Imiquimod, did. Seven studies, examining a total of 82 keloids, investigated their recurrence post excision and application of Imiquimod. The similarity in design allowed for statistical meta-analysis. Meta-analysis revealed a recurrence rate of 39% following application of Imiquimod post scar excision. This result however was imprecise (95% CI = 8.4% to 74.4%) and the analysis showed significant statistical heterogeneity (I2 =87.5%, 95% CI = 75.7% to 92.2%). The use of primary excision and bilayer closure or shave/tangential excision did not alter the outcome as compared to when all studies were examined together. When analysis was conducted based on the location of the keloid scar, earlobe keloids had a recurrence rate of 5.4% (95% CI = 0% to 21.7%), (I2 = 52.9 %, 95% CI = 0% to 82.6%). Remaining keloids excised were predominantly on the trunk and their recurrence rate was higher, at 76.8% (95%CI = 36.1 to 100%), (I2 = 70.5%, 95% CI = 0% to 86.4%). Many of the included studies reported adverse events especially erythema and crusting resulting in a rest period at the two to three week mark. Discussion: Considering the results of this review and the availability and costs of the moisturisers investigated, recommendations are provided for practice. Costly and prescription moisturisers should be selected for application to scars appearing in small and/or cosmetically sensitive areas, such as the face. Clinicians managing scars covering a large surface area should consider readily available, low cost moisturisers that show some evidence of effectiveness. Of those classified as prescription only, based on their availability in Australia, only Doxepin and Putrescine can be recommended, but with reservations. For high cost, over the counter moisturisers, Tretinoin, Wubeize, Lumiere Bio-Restorative Eye Cream, Scarguard® HSE, Provase and Mugwort Lotion can be recommended, but with reservations. Only Alhydran can be recommended with any confidence. The low cost, over the counter moisturisers that can be recommended with reservations are Eucerin® and Cetaphil®. Use of subjective scales far outweigh the use of objective instrumentation among relevant studies. Future research needs to utilise appropriate and available instrumentation in the measurement of outcomes. As the included studies in the narrative synthesis group examined keloid and/or hypertrophic scars, recommendations for specific scar types cannot be provided. Some studies also utilised linear scars, which are commonly normotrophic and therefore were likely to have been resolved without any intervention. Further research is required to examine the effects of basic moisturisers that are regularly in use and readily available to the general public. A small number of these were included in studies as control. It is not known if these moisturisers are just as effective, if not more, than those that are costlier and contain additional specific ingredients.