Free radical is the common name of a large family of molecules known as Reactive Oxygen Species (ROS). These molecules are highly reactive, meaning they have the tendency to interact with other molecules around them such as cellular components, enzymes, proteins, lipids and genetic material; this interaction results in damage. Under normal conditions, there is a balance between these oxidants and our own antioxidant defense system, but this is not always the case; there are two ways in which free radicals can overwhelm our antioxidant defenses:
- Free radicals may be overproduced due to our exposure to environmental factors.
- With aging and with exposure to environmental factors such as UV and ozone our levels of antioxidants decrease making us more susceptible to free radicals induced damage.
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How do free radicals damage the skin?
There are many ways in which free radicals are capable of causing damage to our skin:
- They damage the DNA of the skin cells
- They damage the membrane of the skin cells
- They cause damage to collagen, elastin and other proteins and other components of the dermis such as hyaluronic acid causing their degeneration.
- They decrease the production of collagen
- They interact with receptors in skin cells leading to inflammation
Not only free radicals cause premature aging, but they also cause inflammation and play a role in the development of skin diseases and tumors.
What generates free radicals in the skin?
There are many factors playing a role in free radical formation in the skin. Some are well known such as UV rays, others are less known. The following are the major factors.
Sun light and the skin
UV-A and UV-B light emitted by the sun has many negative effects on the skin. When it comes to oxidative stress, UV rays both generate ROS (reactive oxygen species) and deplete our antioxidant enzymes. UV light accounts only for 3-5% of the total solar radiation reaching the Earth’s surface, while visible light (42-43%) and infrared light (IR – 52-55%) make up for the rest. Both IR and visible light have been found to increase free radicals in the skin, causing damage and pigmentation.
Pollution and the skin
Pollution, to which we are exposed on a daily basis, is another source of oxidative damage for the skin. What we generally call pollution is actually made up of several different chemicals such as:
- Particulate matter (PM 10, PM 2.5)
- Ground-Level Ozone (O3)
- Carbon Monoxide (CO)
- Lead
- Sulfur Dioxide (SO2)
- Nitrogen Dioxide (NO2)
All of these chemicals penetrate the skin to different depths causing a complex cascade of events beginning with free radical formation and ending with a wide variety of oxidative damages and inflammation.
Smoking and the skin
Smoking affects the skin both by reducing blood flow hence decreasing the oxygen delivered to the tissues and due to the many harmful chemicals (over 3,800) inhaled while smoking that among the many also cause the generation of free radicals and the inhibition of antioxidant defenses.
Stress
Although there is not much evidence of the direct effects of stress on the skin, stress is known to cause nervous system and hormonal changes that cause ROS production, immunosuppression, inflammation and DNA damage.
Lack of Sleep
Sleep deprivation is known to increase the risk of several diseases. It is also suggested that during sleep there is an increase in antioxidant activity, while sleep deprivation leads to free radicals accumulation.
Poor Nutrition
Nutritional deficiencies are known to affect the health of the skin. On the contrary, a healthy diet rich in fruits and vegetables, legumes, unsaturated fatty acids and low in sugar and saturated fats may delay aging by providing all essential micronutrients and increasing the antioxidant intake. Alcohol is another dietary factor the leads to premature skin aging.
Temperature
Under normal conditions, the skin temperature is about 33 °C (91 °F); studies show several negative effects of heat on the skin composition both directly and due to oxidative damage. This is also supported by the severe skin aging observed on baker’s arms and glass blowers faces. When out in the sun, the infrared portion of sun light can heat the skin deeply to over 40 °C (104 °F).
What can we do to prevent free radicals from damaging the skin?
We can’t change our genes, but we can change our lifestyle: trying to stick to a healthy diet rich in fruits and vegetables, avoiding alcohol, avoid smoking, sleeping at least 9 hours per night, trying to avoid the sun and always wearing protective clothing and sunscreen, trying to find ways to cope with stress are effective ways to prevent free radical formation both in the body in general and in the skin. The use of cosmetic products containing antioxidant ingredients has also been shown to reduce and prevent aging in clinical trials, check out the dedicated article for more info about antioxidant skincare products.
Sources
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DOI: https://doi.org/10.1016/j.jdermsci.2016.09.015 - Atmospheric skin aging-Contributors and inhibitors.
D McDaniel, P Farris, G Valacchi – Journal of Cosmetic Dermatology, Apr 2018
DOI: https://doi.org/10.1111/jocd.12518 - Irradiation of Skin with Visible Light Induces Reactive Oxygen Species and Matrix-Degrading Enzymes.
F Liebel – Journal of Investigative Dermatology, Jul 2012
DOI: https://doi.org/10.1038/jid.2011.476 - An overview about oxidation in clinical practice of skin aging.
SAMe Silva – Anais Brasileiros de Dermatologia, Jun 2017
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