By: Jessica J.
Affecting more than 50 million Americans annually, acne is the most common skin condition. While most people are familiar with the ailment, many are unaware of the actual prevalence and pathogenesis of it.
Acne typically appears on the face, neck, chest, shoulders, and/or back. Due to the way acne develops, it most typically appears on the face. Acne is a skin disorder that can occurs when the pores under the skin get clogged from bacteria or dead skin cells, resulting most commonly in skin blemishes.
Human skin contains many sebaceous glands, and there can be as many as 900 sebaceous glands per square centimeter on certain skin areas. Their function is to produce and exude sebum (a mixture that includes many complex elements such as: triglycerides, fatty acids, wax esters, squalene, and cholesterol), with the purpose of lubricating and protecting the skin’s moisture (Makrantonaki, et. al, 2011). The increase in sebum production can lead our pores to become blocked. Which can get clogged with dead skin cells or infected by bacteria that are naturally found on our skin, such as Cutibacterium acnes or C. acnes (it is also the most common bacteria that is known to cause acne), Corynebacterium acnes, and Staphylococci (Platsidaki & Dessinioti, 2018). The reaction leads to swelling, redness, and inflammation of the skin.
Role of P. acnes in the development of acne symptoms.
Diagram by Otsuka Pharmaceutical company.
Retrieved from: Otsuka
Caption: "Normal bacteria that are usually present on your face such as P. acnes can be found even in normal pores, however if abnormal keratinization happens at the pore’s exit it becomes a comedone. When the P. acnes multiplies it can cause inflammation, this leads to a papule. As the inflammation increases the wall of the pore breaks down, causing the inflammation to proliferate and become pustules.”
Acne symptoms can be split up into two major groups--non-inflammatory and inflammatory. Non-inflammatory symptoms include blackheads (open comedones) and whiteheads (closed comedones). A comedone is basically an enlarged hair follicle filled with sebum. A blackhead gets its appearance because the top of the pore is open which causes a reaction with the oxygen in the air. Whiteheads are comedones that have not pushed through the skin’s surface, but have a protruding bump appearance, and the material inside it is not oxidized. Inflammatory symptoms are essentially pimples that are red and swollen, caused and aggravated by the various bacteria.
Acne Vulgaris Non-Inflammatory Symptoms. Diagram by Harvard Health.
Retrieved from: Harvard Health Publishing
Acne Vulgaris Inflammatory Symptoms. Diagram by The Acne Lab.
Retrieved from: The Acne Lab
Various factors can trigger the development of acne. A study done by a group of researchers from Kunming Medical University concluded the determinants can be grouped into four main categories such as socio-economical and biological, natural environmental, social environment, and built environmental factors. Socio-economical and biological factors include: “gender, age, economic level, heredity, obesity, skin type, cosmetics products, sleep products, and overall physiological factors.” Natural environmental factors include: “temperature, humidity, sun exposure, air pollution and chloracne.” Built environmental factors include population density, food stores, green spaces, and other built environment features for transport (Yang, et. al, 2020).
The skin is a very important organ and plays a protective role as it serves as our first defense against external aggressors (ex. pathogens, changes in temperature and humidity, UV rays, etc. ) and their influences. Therefore the influence of exposome, a term used for the measure of the collective exposures of an individual during their health, due to environmental and occupational sources ,on the skin is a very essential detail in understanding the effect of natural environments on the skin and acne. A study done by Dreno et al. in 2018 found environmental factors to have a heavy influence on acne characteristics such as frequency, and appearance.
A pollutant is a “substance that is present in concentrations that may harm organisms (humans, plants, and animals) or exceed an environmental quality standard.” (OECD, 2005). The pollutants that most commonly affect the skin are air pollutants. Air pollution results in the skin being exposed to “ultraviolet radiations and environmental pollutants (such as hydrocarbons, volatile organic compounds, oxides, particulate matter, ozone, and cigarette smoke). The prolonged and repetitive exposure to them results in exceeding the skin’s usual defensive potential. Increasing the oxidative stress on the skin results in major alterations to the normal function of lipids, DNA and/or the proteins in the human skin (Drakaki, et al. 2014). Two clinical studies conducted by Lefebvre et al. done in Mexico and the Shanghai area concluded changes in skin quality after extended air pollution exposure. The exposure to air pollutants also showed an increase in sebum levels, and greater appearance of both non-inflammatory and inflammatory acne symptoms. There is a high correlation between air pollution and its influence on acne.
Oxidative Stress Phases. Retrieved from: Helvetica Health Care
Apple visualization of the process of oxidation.
Retrieved from: Genomic Medicine Works
Climatic conditions such as sun exposure/UV light exposure, heat, intense, temperature and humidity have been linked to the development of acne. An increased amount of sunlight exposure also means an increased exposure to UV light. While receiving vitamin D from moderate sunlight exposure is vital to the skin, exceeding the moderate amount can hurt the skin. The increased exposure to ultraviolet light has been known to create an increase in the number of cells (hyperplasia) in the sebaceous glands, thicken the outermost layer of the epidermis, increase sebum secretion, which overall increases the amount of comedones (Lee, et al. 2013). This happens because the UV cells target the cells and molecules of the skin, and trigger the production and release of antimicrobial peptides, that activate the innate immune system, and end up suppressing the adaptive cellular immune response. As a result, there is an increase in the skin microbiota because it multiplies and eventually causes acne.
UVA and UVB can penetrate deep into the skin.
Retrieved from: Mission to Mars at Duke University Medical Center
Discussion Question:
How do environmental aspects affect the biological factors of acne?
How could certain factors (such as the ultraviolet light) cause other skin conditions (ex. skin cancer)?