Free Radicals

Written by: Dr. Leslie Baumann



Time to read 7 min

In the world of skincare, the term "free radicals" is often thrown around, but what exactly are they, and why should we care? In this blog post, we'll dive deep into the science of free radicals, also known as reactive oxygen species (ROS), and explore their impact on our skin's health and appearance. We'll discuss what causes free radicals, why they're harmful, and most importantly, what we can do to protect our skin from their damaging effects of ROS.

ROS: Reactive Oxygen Species

In the skin care world, you will often see the term ROS when free radicals are discussed.  This is because oxygen is a common free radical. When it loses an electron, it becomes reactive. Just as we need chocolate or food when we become reactive, oxygen needs to be given an electron to calm down.

What are Free Radicals?

Free radicals are molecules, usually made from oxygen, that are missing an electron, making them highly unstable and reactive. In a sense, they're like a person craving a piece of chocolate, searching relentlessly for that missing element to feel complete. In their quest for stability, free radicals will steal electrons from other molecules in our skin, setting off a chain reaction of damage.

Causes of ROS

Free radicals can be generated by both internal and external factors. Internally, our bodies produce ROS as a natural byproduct of cellular metabolism. However, external sources such as UV radiation, air pollution, cigarette smoke, and certain medications can greatly increase the production of free radicals in our skin.


Oxidation is a fundamental chemical process that involves the loss of electrons from a substance. When a molecule loses electrons, it becomes oxidized, which means it has undergone oxidation. In the realm of skincare, oxidation can be triggered by a variety of factors, such as exposure to UV radiation, air pollution, and certain chemical reactions between incompatible ingredients.

When a skincare product becomes oxidized, it means that its chemical composition has been altered, often leading to a decrease in its effectiveness and potential harm to your skin. Oxidized products may change color, odor, or texture, indicating that their ingredients have broken down or reacted with one another in an undesirable way.

The process of oxidation often results in the formation of free radicals, which are highly reactive molecules that can damage skin cells and contribute to premature aging. Free radicals are unstable because they have an unpaired electron, causing them to seek out other molecules to steal an electron from, thus oxidizing them in turn. This chain reaction of oxidation and free radical generation can lead to oxidative stress, a state in which the skin's natural defenses are overwhelmed, and cellular damage accumulates.

Skin Care Products Can Cause ROS

Certain skin care products such as benzoyl peroxide cause oxidation. You can also generate free radicals when you mix certain ingredients together.  This is why your skin care routine design maters so much. If you take out skin type quiz, we can help you design a skin care routine to avoid these issues.

Incompatible Ingredients Cause ROS

Using the wrong skin care products in your skin care routine can cause free radicals. It's essential to be mindful of the products you use together in your skin care routine and how you combine them. Certain ingredients, such as benzoyl peroxide and hydrogen peroxide, can oxidize other components in your skincare products when mixed together. This oxidation process can lead to the formation of free radicals, causing oxidative stress and potential damage to your skin.

For example, using benzoyl peroxide in combination with ascorbic acid (vitamin C) can cause the ascorbic acid to oxidize, rendering it less effective and potentially harmful. When exposed to benzoyl peroxide, ascorbic acid undergoes a chemical reaction that transforms it into dehydroascorbic acid, which is an inactive form of vitamin C. This oxidation not only diminishes the antioxidant benefits of ascorbic acid but can also generate free radicals that can damage your skin cells.

You can read more about using retinol, Vitamin C and niacinamide together here.

Why not to use Benzoyl peroxide and Vitamin C Together

Sunscreen and Free Radicals

Chemical sunscreens have been shown to generate free radicals when exposed to UV radiation. They longer you are in the sun, the more likely this is. In some cases the ROS generated by SPF will cause other ingredients to change into allergens. This phenomenon is known as phototoxicity, and it can lead to oxidative stress and skin damage to your skin cells. To minimize this risk, consider opting for physical (mineral) sunscreens that contain ingredients like zinc oxide or titanium dioxide. These sunscreens work by reflecting UV rays away from your skin, rather than absorbing them like chemical sunscreens do. 

Oxygen May Increase Oxidation

Oxygen is essential for healthy skin, as it plays a crucial role in cellular respiration and energy production. However, the use of topical oxygen in skincare products has been a topic of debate among skincare professionals and researchers. Some products claim to deliver oxygen directly to the skin, promising to revitalize and rejuvenate the complexion. While oxygen is necessary for skin health, the idea that applying topical oxygen can benefit the skin is questionable.

In fact, the use of topical oxygen on the skin may actually increase the production of reactive oxygen species (ROS). When oxygen molecules are applied to the skin, they can react with other molecules and generate ROS, such as hydrogen peroxide and superoxide anion. These ROS can cause oxidative stress, leading to cellular damage, inflammation, and premature aging.

Why Oxidation and Free Radicals Are Harmful

When free radicals steal electrons from other molecules in our skin, they cause oxidative damage to crucial components like DNA, proteins, and lipids. Over time, this damage accumulates, leading to visible signs of aging such as fine lines, wrinkles, and uneven skin tone. Free radicals can also break down collagen and elastin, the proteins responsible for keeping our skin firm and youthful-looking.

Preventing Free Radical Damage

While it's impossible to completely avoid exposure to free radicals, there are steps we can take to minimize their impact on our skin. One of the most important things you can do is protect your skin from UV radiation by wearing a broad-spectrum sunscreen with an SPF of at least 30 every day. Also use antioxidant ingredients in your skin care routine. Adopting a healthy lifestyle that includes a diet rich in fruits and vegetables, regular exercise, and avoiding smoking and excessive alcohol consumption can help reduce the production of free radicals in the body.

Free radicals may be tiny molecules, but their impact on our skin's health and appearance is significant. By understanding the science behind these reactive oxygen species and taking steps to prevent and combat their damaging effects, we can help our skin look and feel its best for years to come. Incorporating antioxidant-rich skincare products, adopting a healthy lifestyle, and practicing daily sun protection are all powerful tools in the fight against free radicals.

While antioxidants are a crucial weapon in the fight against free radicals, they work best as part of a protective personalized skincare routine.

Level up your skin care knowledge with medical advice from dermatologists

How to reduce free radicals in skin?

Avoid ultraviolet radiation and take oral antioxidants and use topical antioxidants like Vitamin C.  Also avoid getting inflammation of the skin.

What causes free radicals in the skin?

Ultraviolet light, inflammation. and natural cellular processes lead to free radicals in the skin. 

What are the best antioxidants to look for in skincare products?

There are many good antioxidants to use in your skin care routine. It is best to combine many different ones internally and externally. Here you can find a list of good antioxidants used in skin care.

Can a diet rich in fruits and vegetables help protect my skin from free radical damage?

Yea your diet can help protect your skin from free radicals.

What are the best skin care products to protect skin from free radials?

The best way to protect skin from reactive oxygen species in your skin care routine is with anti-inflammatories, antioxidants, and sunscreen. You also need ingredients to help the skin repair itself such as DNA repair enzymes, Coenzyme Q10, and niacinamide.

Best References and Scientific Publications on free radicals

  1. Baumann L. Antioxidants in Ch. 37 of Baumann's Cosmetic Dermatology Ed 3. (McGraw Hill 2022)
  2. Baumann, L. Ch. Cosmeceuticals and Cosmetic Ingredients (McGraw Hill 2015)
  3. Baumann, L. (2005). How to prevent photoaging?. Journal of Investigative Dermatology125(4), xii.
  4. Baumann, L. (2007). Skin ageing and its treatment. The Journal of Pathology: A Journal of the Pathological Society of Great Britain and Ireland211(2), 241-251.
  5. Baumann, L. (2018). How to use oral and topical cosmeceuticals to prevent and treat skin aging. Facial Plastic Surgery Clinics26(4), 407-413.
  6. Baumann, L. (2009). The Baumann skin-type indicator: a novel approach to understanding skin type. Handbook of Cosmetic Science and Technology, 3rd Edition, Informa Healthcare, New York, 29-40.
  7. Baumann, L. (2008). Understanding and treating various skin types: the Baumann Skin Type Indicator. Dermatologic clinics26(3), 359-373.
  8. Poljšak, B., & Dahmane, R. (2012). Free radicals and extrinsic skin aging. Dermatology research and practice2012.
  9. Emerit, I. (1992). Free radicals and aging of the skin. Free radicals and aging, 328-341.
  10. Nakai, K., & Tsuruta, D. (2021). What are reactive oxygen species, free radicals, and oxidative stress in skin diseases?. International journal of molecular sciences22(19), 10799.
  11. Herrling, T., Jung, K., & Fuchs, J. (2006). Measurements of UV-generated free radicals/reactive oxygen species (ROS) in skin. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy63(4), 840-845.
  12. Packer, L. (Ed.). (1994). Oxygen radicals in biological systems (Vol. 233). Elsevier.

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