The fundamental understanding of the effects of photodamage and aging on skin that has occurred over the past few decades has led to the identification and commercialization of various technologies that have a mechanistic rationale for potential treatment effects, including reversal of the appearance of fine lines and wrinkles and pigmentary disorders. These range from actual physical agents that either remove varying layers of the stratum corneum and epidermis to stimulate a wound repair process or directly restore the ECM content in thinned dermis of photodamaged skin. Hydroxy acids, such as salicylic, lactic, and phenol, have been used in ranges of concentrations to remove varying depths of the epidermis. Under extreme situations, in which a significant portion of the epidermis is removed, there are dramatic effects in reducing the amount of fine lines and wrinkles and the evening of texture and pigmentation. However, there can be significant side effects of skin burns, thereby limiting the actual physical levels of these materials in cosmetic products and thus rendering them somewhat effective but limited. Other types of materials that act in a physical and acute manner (benefits observed immediately) are dermal fillers. These types of materials are injected directly into the dermis of facial skin and include collagen, hyaluronic acid, and microspheres, the last of which provides more permanent effects. Another type of injec – tionable agent is Botox, the bacterial botulinum neurotoxin. Upon injection, the neurotoxin causes a temporary relaxation of muscles in the skin by blocking neural stimulation, thereby allowing the skin to relax and essentially makes fine lines and wrinkles unnoticeable.
More selective technologies that are connected to aspects of collagen synthesis include retinoids, ascorbic acid, and peptides, all of which have been shown to stimulate or enhance collagen synthesis from dermal fibroblasts in vitro and/or in vivo. In addition, there are numerous antioxidant-based technologies that in theory would impact the oxidative stress generated in the skin from UV and intrinsic aging. A more specific example includes niacinamide, which was identified based on its ability to restore the imbalance in key redox regulators that occur in aged skin. Relative to pigmentation, the usage of bleaching agents such as hydroxyquinone can be very effective in gross alteration of pigmentation but more selective agents such as retinoids, vitamin C analogues, and glucosamine derivatives can be used cosmetically with reduced negative side effects.
The last decade has seen a literal explosion of knowledge and development in the safe usage of devices in the professional marketplace to treat various skin ailments, including photodamage. This area is reviewed in more detail in Chapter 15 but essentially this methodology has significantly impacted the professional aesthetics marketplace financially as well as by providing to patients treatments that are both less invasive and deliver significant efficacy.
In the long run, continued understanding of the mechanisms and signaling pathways that are impacted in skin as a function of photodamage and intrinsic aging will provide additional mechanistic insight that should lead to more effective technologies. Equally important is that these technologies would be selective in their action, thereby in theory allowing for safe usage by consumers of both cosmetic and drug products. A separate but related, aspect is the continued development of home-use energy emitting devices that, either alone or in combination with topical agents, will provide to the consumer an even better arsenal to combat the ravages of time and environmental damage.