Environmental Factors Impact on Skin Part 1
The environment can influence skin health by inducing changes on the cellular level, which can have lasting consequences. Often working in synergy, factors such as cold temperature, low humidity, and pollution, can affect skin hydration, morphology, and function.
REACTIVE OXYGEN SPECIES & POLLUTION
- Reactive Oxygen Species (ROS) are a natural occurrence in the body and are essential for cellular health at low concentrations. However, pollution, along with other environmental factors such as UV, can increase these levels causing these species to do more harm than good.
- Unstable by nature, ROS can oxidize important molecules present in the skin such as lipids and proteins, depleting skin barrier function.
- ROS can also be responsible for cellular damage. Furthermore, the natural defenses of cells in the form of antioxidant enzymes are often reduced by pollution, as well as the actual antioxidants, including glutathione and ascorbic acid.
SKIN MICROBIOME, POLLUTION & ALTITUDE
- In the uppermost layer of the skin called the stratum corneum, there are colonies of good bacteria that facilitate proper skin function known as the microbiome.
- The composition of this microbiome is dependent on factors such as age, location on the body, and lifestyle, and it constitutes an integral part of the human immune system.
- When excessive pollution comes in contact with the microbiome, it creates an environment which favors the growth of harmful bacteria, or pathogens such as Staphylococcus and Streptococcus varieties. These can then lead to skin conditions such as cellulitis and acne.
- Air pollution can also decrease the size of the microbiome, exemplified by a 50% decrease observed in a study of ozone exposure.
- High altitudes are associated with skin microbiome that has lower diversity. This development can be the result of selective evolution for typical environmental characteristics such as lower oxygen concentrations, lower temperatures, and greater ultra-violet radiation exposure.
INFLAMMATION & POLLUTION
- Some pollutants can penetrate deeper layers of the skin triggering inflammation by activating the Aryl Hydrocarbon Receptor (AhR) pathway. These receptors are a natural defense against toxins and pollution, as they prompt the production of cytokines, including certain interleukins, which, when activated for extended periods, can cause skin damage.
- Skin lesions and inflammatory skin conditions such as psoriasis and atopic dermatitis are all associated with increased activity of these receptors.
- Other inflammatory markers activated by pollution include transforming growth factor (TNF-alpha) and prostaglandins. Extended exposure to these markers is associated with skin aging and skin cancer.
- Air pollutants are also able to sit on the top of the skin, clogging pores and preventing oxygen permeation, creating a favorable environment for acne flares.
SKIN BARRIER FUNCTION, HUMIDITY & TEMPERATURE
- Filaggrin, an essential protein in skin barrier function, is more available in low humidity environments, which leads to increased NMF levels.
- The skin adapts to long term exposure to dry environments by developing a thick stratum corneum to decrease Transepidermal Water Loss (TWL) and increase skin barrier function.
SKIN HYDRATION, HUMIDITY & TEMPERATURE
- When exposed to low humidity, skin hydration decreases, which consequently causes more sebum production to combat the loss of moisture. Such changes can be observed after 7 hours in a 30% relative humidity environment.
- The capacity for the skin to hold water is not dependent on age according to a study of Chinese women aged 20 to 70 years. Instead, low humidity and cold temperatures were the primary causes of skin dryness observed in their Beijing sample compared to the Guangzhou sample, which lived in a hotter, more humid climate.
- Women between 20 and 30 years old exhibited considerable variation in sebum production in the winter and summer, but this variation decreased significantly for those more than 40 years.
- Inflammatory skin conditions such as dermatitis are associated with low levels of Natural Moisturizing Factor (NMF), which often decrease in the winter. However, these levels are generally higher in older people after taking into account the environment.
- Females also tend to have higher levels of NMF than males, after taking into account the general increase in NMF in the summer.