INTRODUCTION
Although the importance of protecting the skin from sunlight is widely recognized, ultraviolet (UV) light is the main cause of skin damage and premature aging. However, many other outdoor stressors have also been shown to affect skin health and compromise its physiologic properties. It is necessary to take into account that, over the course of an individual’s life, they are exposed to a wide range of non-genetic factors that can affect health. These factors, which are referred to collectively as the “exposome,” can contribute to skin damage, and include infrared radiation, ozone pollution, exhaust emissions, cigarette smoke, transition metals, inadequate nutrition, psychological stress, and even lack of sleep (Figure 1).1 Therefore, a more comprehensive approach to skin protection, extending beyond the use of sunscreen, is necessary to preserve optimal dermatologic health in the face of the diversity of environmental stressors.2
The Need for Comprehensive Skin Protection
Skin damage caused by sun and environmental exposure is brought about primarily by a cascade of reactions involving the generation of reactive oxygen species (ROS), which leads to peroxidation of cellular components, such as lipids, proteins, and nucleic acids.3 Altering the lipid composition of skin can compromise the epidermal barrier, leading to serious skin damage.2 In general, premature skin aging is characterized by visually macroscopic signs, such as rough texture, wrinkling, discoloration, and larger pores. The effects of exposure to outdoor stressors begin earlier in life than many people may realize; signs of aging can already be detected at around age 18 years to 25 years.
Therefore, a comprehensive approach to skin protection is needed to counter the damage caused by environmental stressors. In addition to daily use of sunscreen to prevent UV damage, inclusion of antioxidants and metal chelators in the routine skincare regimen is also necessary to decrease premature aging of the skin.6
The inflammatory process triggered by the exposome can further contribute to skin aging through a process referred to as “inflammaging,” which is directly correlated to the altered redox homeostasis of the tissue.4 In addition, this process may also exacerbate other inflammatory conditions such as eczema, psoriasis, or acne.5,6
Some components of the exposome that contribute to skin aging are usually modifiable. For example, individuals can take steps to improve their nutrition or sleep hygiene, and they can even limit their exposure to direct sunlight. However, pollution in the environment presents a much more complex challenge. There are multiple environmental pollutants and they have varying chemical, biological, and physical effects that contribute to skin damage. There is little that individuals can do to avoid these pollutants and, because they have differing mechanisms of activity, their individual effects on skin tissue appear to be additive and, in some respects, synergistic.7
Therefore, a comprehensive approach to skin protection is needed to counter the damage caused by environmental stressors. In addition to daily use of sunscreen to prevent UV damage, inclusion of antioxidants and metal chelators in the routine skincare regimen is also necessary to decrease premature aging of the skin.6
Mechanisms of Environmental Skin Damage
The specific mechanisms by which skin damage occurs can differ among individual environmental pollutants. The mechanisms
