From Earth to Skin: Reviewing the Role of Environmental Factors in Dermatologic Conditions

Each year, April 22 is recognized globally as Earth Day.

Environmental factors such as temperature, weather, climate, and sun exposure all play a crucial role in the onset, exacerbation, and even relief of various dermatologic conditions. Human-made, or "built" environmental factors, such as the presence of lack of green spaces and air pollution, coupled with the changing climate, also play a role.

This Earth Day, Dermatology Times is taking a look at recent studies and conversations surrounding the role of the natural and built environments in skin conditions. We review its roles in atopic dermatitis, pigmentary disorders, aging skin, psoriasis, urticaria, and acne.

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Exposure to Heavy Traffic Affects Risk of Atopic Dermatitis

A study conducted last year by researchers from National Jewish Health in Denver, Colorado, found that living at least 1000 meters away from high-traffic roadways may reduce the risk of developing atopic dermatitis (AD) by 26.1%. The study, published in the Journal of Allergy and Clinical Immunology,¹ analyzed over 14,000 pediatric patients in the Denver area over a 13-year period. Researchers compared patients with AD to a control group without AD, considering their proximity to major roads using geocoded coordinates. They discovered that for every tenfold increase in distance from a major roadway, there was an 18.8% decrease in the odds of having AD.

Environmental Factors Affecting Pigmentation And The Skin Exposome

Arianne Shadi Kourosh, MD, MPH, FAAD, a former high school chemistry teacher turned dermatologist and Harvard Medical School professor, presented on the impact of environmental factors on the skin at the 2024 American Academy of Dermatology Annual Meeting. She discussed the effects of visible light, infrared radiation, location, and pollution on skin health.

Visible light, constituting half of solar radiation, penetrates deeply into the skin, causing DNA oxidation, generating reactive oxygen species, and affecting collagen and elastin fibers, leading to pigmentation changes, especially in darker skin types. Pollution, particularly air pollution, poses direct threats to skin health, with pollutants such as particulate matter, ozone, and volatile organic compounds contributing to pigment spot formation, wrinkle formation, and depletion of antioxidants.

Infrared radiation, which makes up 45% of solar radiation, penetrates deeply into the dermis and can damage collagen and elastin fibers, exacerbate pigmentation disorders such as melasma, and contribute to skin aging. Location plays a significant role, with proximity to the equator and altitude affecting the severity of skin damage due to differences in UV exposure. Reflective surfaces such as snow and sea foam further increase UV radiation exposure.

Sun Exposure, Pollutants, and Skin Aging

Jennifer Holman, MD, FAAD, a specialist from the Center for Aesthetic and Laser Medicine in Tyler, Texas, highlights how various environmental factors impact skin health and aging.³

Sun exposure, particularly to UVA and UVB rays, is the primary cause of accelerated skin aging. Additionally, infrared and blue light, emitted by electronic devices, can also contribute to skin aging. Airborne pollutants, especially in urban areas, can lead to premature aging by damaging healthy skin cells and causing dark spots and wrinkles. Preventing accelerated skin aging involves combating oxidative damage caused by environmental factors.

Psoriasis, Weather, and Short-Term Exposure to Pollutants

Short-term exposure to air pollutants was linked to increased cases of psoriasis among outpatients, according to a study published in Frontiers in Public Health.⁴ This suggests that individuals, especially those at higher risk for psoriasis, should limit their outdoor activities and enhance their skin protection measures during periods of poor air quality.

According to the National Psoriasis Foundation, weather may play a role in triggering or relieving symptoms of psoriasis in some patients. Colder, cooler weather may lead to the onset of flares due to a lack of humidity and sunlight. On the other hand, warmer conditions with ample natural sunlight and high humidity may ease symptoms of psoriasis, leading to improvements in some patients.⁵

Heat, Cold, and Sunlight Play Roles in Urticaria

In cases of patients with urticaria, precipitants, such as weather and exposure to sunlight, play a role in the onset or effectiveness of certain treatments.⁶ Temperatures such as extreme heat or extreme cold are considered factors, while an excess of exposure to sunlight may also trigger urticaria.

Natural Environmental Factors as a Pillar of Acne Influence

According to researchers Yang et al, influencing factors for the onset and development of acne in patients can be divided into 4 main pillars. While the other pillars include individual socio-economic and biological factors, social environmental factors, and built environmental factors, the effects of natural environmental factors can be profound.⁷

Temperature, humidity, sun exposure, and air pollution can all be considered triggers and exacerbate acne in patients. "Built" environmental factors, such as green spaces in crowded and more densely populated areas, may present negative opportunities for UV exposure in individuals with acne, and public transport may have detrimental impacts on air pollution, which in itself is considered a trigger for acne.

References

1. Nevid M, Hui J, Crooks J, Goleva E, Rabinovitch N, Leung D. Association of atopic dermatitis with proximity to major roads. J Allergy Clin Immun. 2023. Accessed April 22, 2024. doi:10.1016/j.jaci.2022.12.604
2. Kourosh A, Tsao S. Fifty shades of brown: science, symptoms, and strategies for acquired pigmentary disorders. Presented at: 2024 American Academy of Dermatology Annual Meeting; March 8-12; San Diego, CA.
3. US Dermatology Partners. Environmental causes of skin aging. September 20, 2023. Accessed April 22, 2024. https://www.usdermatologypartners.com/blog/environmental-causes-of-skin-aging/
4. Wang T, Xia Y, Zhang X, et al. Short-term effects of air pollutants on outpatients with psoriasis in a Chinese city with a subtropical monsoon climate. Front Public Health. December 22, 2022. Accessed April 22, 2024. doi:10.3389/fpubh.2022.1071263
5. National Psoriasis Foundation. Causes and triggers. Accessed April 22, 2024. https://www.psoriasis.org/causes/
6. Wong HK. Urticaria. Medscape. Updated September 16, 2020. Accessed April 22, 2024. https://emedicine.medscape.com/article/762917-overview#:~:text=Precipitants%2C%20such%20as%20heat%2C%20cold,or%20other%20nonurticarial%20dermatologic%20disorders
7. Yang J, Yang H, Xu A, He L. A review of advancement on influencing factors of acne: An emphasis on environment characteristics. Front Public Health. September 17, 2020. Accessed April 22, 2024. doi:10.3389/fpubh.2020.00450