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There is increasing evidence documenting the effects of ‘antiaging’ cosmetic moisturizers on the signs of photodamaged skin. Typical agents used in these moisturizers include hydroxyacids,[1, 2] retinol, and its esters,[3, 4] salicyloylphytosphingosine, peptides,[6-9] adenosine, niacinamide, creatine and folic acid, peroxisomal proliferator activated receptor agonists, hyaluronic acid fragments, and a variety of antioxidants including ascorbic acid and lipoic acid. Many of these agents have complex effects on the skin ranging from increasing dermoepidermal membrane restructuring through to inhibition of matrix metalloprotease activity and improving epidermal differentiation all of which are perturbed in photodamaged skin. However, these improvements are usually expressed to the consumer as reduced number and/or depth of wrinkles, more even skin tone, reduced hyperpigmentation together with smoother, firmer, and more luminous skin.
Until recently, however, the relative effects of these actives were considered to be inferior to the effects of retinoic acid. Nevertheless, the use of a niacinamide, peptide, retinyl propionate product regime was found to be as effective as that of retinoic acid in alleviating the signs of skin photodamage. Importantly, although, all these treatments, including the retinoic acid prescription products, are emulsion-based products and as far as we are aware there is no reported study of the effect of a totally anhydrous cosmetic antiaging moisturizing oil alleviating the signs of skin photodamage.
Antioxidants and retinyl palmitate were included in the oil for their potential effect in alleviating the signs of skin photodamage. However, as it has been reported recently, in a longitudinal study that simply having a drier cheek stratum corneum (SC) was predictive of more persistent skin wrinkling 8 years later, we considered that the simple moisturizing effect of the anhydrous moisturizing oil would also be effective in the treatment of aged skin. To demonstrate its effectiveness, we performed a randomized, controlled and efficacy grader-blinded clinical study examining the changes in skin condition of the face, neck, décolletage, lower legs, and the arms over a 12-week period compared to a no-treatment control group. We believe this is the first report of its kind demonstrating the improvements in the signs of skin photodamage of a cosmetic anhydrous antiaging moisturizing oil on both facial and body skin sites while at the same time recording the changes in skin condition for a no-treatment group over the same time period.
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To our knowledge, this is the first study demonstrating the effect of a cosmetic anhydrous antiaging moisturizing oil on the signs of photodamage on the face, neck, décolletage, arms, and lower legs. Compared to the no-treatment group, and to baseline, the oil improved fine lines, coarse wrinkles, mottled pigmentation, uneven skin tone, roughness, firmness and clarity of the skin on the face and neck and was also shown to improve crepey skin texture, dryness, scaling and roughness on the décolletage, arms and lower legs. The efficacy of the product appeared to be greater for the face compared with the neck for improvements in wrinkling scores, but similar for the skin color problems. This relative responsiveness on the different body sites would appear to be similar in other clinical studies using intense pulsed light. Grading of the photographs supported the live grading results. The roughness and dryness improvements were easier to treat on the legs than on the arms and the décolletage suggesting greater photodamage to the latter body site and thereby less responsiveness to treatment. In general, the décolletage appeared to be more difficult to treat and appeared to behave similar to the face and neck in terms of skin grading improvements. The neck was slightly harder to treat in terms of grading. In terms of overall numbers of subjects that improved on the face, neck, décolletage, legs and arms 94.3%, 80%, 88.6%, 88.6%, and 88.6% of subjects improved whereas only 25%, 31%, 25%, 15.6%, and 21.9% of subjects improved in the no treatment group.
The study was a grader-blind study and all product treatments were stopped 10–16 h before any skin assessments were made. The consistency in improvements in skin condition for all body sites implies the cosmetic oil can dramatically improve the signs of photodamaged skin. Similar effects can be also observed from the emulsion-based vehicle treatment groups for other reports,[1-17] but this study compares the improvements in photodamage to a no-treatment control group for the first time. As can be observed cumulative improvements are found with increasing treatment on all body sites.
The SC has been proposed to play an important role in wrinkle formation and indeed having a drier cheek SC has been shown to be predictive of more persistent wrinkling over an 8-year period. Fine wrinkle formation has been linked to the dryness of the SC and increased expression of fine wrinkles are observed in low humidity compared with high humidity environments. Moreover, its water holding capacity and elasticity decreases after repetitive UV exposure making it prone to wrinkle formation. Decreases in SC levels of filaggrin and natural moisturizing factors are known on photodamaged skin sites, which will reduce its mechanical properties. Deterioration in the fibrous ultrastructure of the keratin intermediate filaments has been reported to be caused by repetitive UVB irradiation associated with an increased skin wrinkling. Changes in keratin patterns have been followed after UV irradiation and increased expression of K6 and K16 were apparent.[24, 25] As these keratins are not as mechanically resilient as the normal K1/K10 pair, then these have also been associated with a loss in the elasticity of the epidermis. All these events are associated with a less flexible and more brittle SC. Moreover, computational models have been developed that show a decrease in SC modulus by 50% is likely to reduce wrinkle formation. This level of improvement in skin elasticity may be expected following moisturization of the skin, but equally lessening repetitive stress after moisturization may allow repair of wrinkles already formed.
Photoaged skin contains significantly fewer levels of basement membrane molecules at the dermoepidermal junction between the epidermis and dermis, such as collagens, fibrillins, and glycosaminoglycans etc., which are believed in part due to increased cutaneous expression of MMPs. These changes are likely initiated from the increased oxidative stress from the solar irradiation and the consequent activation of aberrant transcription factor signaling pathways, such as increased AP-1 and NfκB, which also lead to increased levels of inflammatory cytokines. Simple moisturization by occlusion, the primary mechanism of action of the oil used in this study, is likely to dampen these responses. Changes in epidermal cytokines are known in a variety of model systems. For instance, occlusion significantly decreased the epidermal expression of the profibrotic cytokine interleukin-1 beta and increased the epidermal expression of the antifibrotic cytokine tumor necrosis factor alpha in a rabbit hypertrophic scar model, a wrinkle has been considered to be a solar scar. These alterations in the epidermal gene expression also resulted in concomitant changes in the expression of the transforming growth factor-beta family members by cells in the dermis, resulting in a decrease in profibrotic signaling within the dermis.[29-31]
Nevertheless, improvements in skin aging biology are expected from the use of some of the ingredients in the product. Retinoic acid after it conversion from retinyl palmitate may be acting on the retinoic receptors. Alternatively retinyl palmitate with its UV radiation absorbing capacity or acting as an antioxidant together with other antioxidants in the oil may be contributing to the benefit. Vitamin E acetate is used in oil but it is widely known that it needs to be hydrolysed to free tocopherol to deliver its effects. This is known to occur only after several days of application and after its penetration into skin. Most recently, it has been shown to reduce protein carbonyls in the skin but that the acetate has less activity than the free tocopherol. Nevertheless, the acetate is used for product stability reasons. Bisabolol is another antioxidant in the product, which has been shown to reduce skin pigmentation. This together with the other ingredients may be helping in the reduction in mottled hyperpigmentation throughout the study.
However, this study was not designed as a vehicle-controlled study and as such; we cannot ascribe the efficacy of the moisturizing oil to any of its particular ingredients. Nevertheless, there is no reason to suspect that the vitamin A ester or other antioxidants would not be efficacious in a totally anhydrous oil format as they are in emulsion-based products. The product was effective not only compared to its own baseline but also to a no-treatment control group (which was primarily used to evaluate any potential changes in the environmental conditions during the time course of the study). We believe that the changes observed between the treatment and the no-treatment control group are real and that the changes observed in the treatment group are not just an emollient effect from the oil. The last application of the product in the treatment group was the evening before any assessment and subjects had also cleansed their skin the morning before any assessment thereby minimizing the presence of any likely residual oil that would mask any of the signs of aging. This is further corroborated by the cumulative improvements in the parameters graded for the signs of skin aging. This cumulative effect would not have been apparent if this was not the case.
Irrespective of the potential mechanisms of action, these studies provide the first evidence that the use of a cosmetic anhydrous antiaging moisturizing oil is able to provide a clinically identifiable improvement in the appearance of the signs of photodamaged skin. Not only that, differences in the relative performance occurs on different body sites with the arms and legs being easier to treat than the décolletage, neck and face probably due to the differences in levels of skin photodamage across these body sites.