What is the Function of Skin as a Protective Barrier

What is the Function of Skin as a Protective Barrier?

By Britton Strickland, Ph.D.

FEB 12, 2023

Our skin’s outermost layer–known as the skin barrier–is responsible for regulating and protecting our bodies from the outside world. Skin is unique compared to our other organs in that we are largely able to observe its status and health visually; however, there is much more to the skin’s structure and function than meets the eye.

In this blog, we’ll discuss the structure of the skin barrier, how many layers of protective barriers exist in our skin, and the function of the skin as a protective barrier. We’ll also discuss how to incorporate different topical skin care products, foods, and lifestyle choices to nurture all layers of the skin and keep our skin barrier functioning as best as possible.

Why is the skin barrier important?

Our skin is the outermost and largest organ in the body. It protects us from external stressors and pathogens, regulates our body's functions and homeostasis, and provides us with sensations vital to our survival. One of the skin’s most important functions is its role as a barrier against external factors such as UV rays, pollution, infection-causing pathogens, and physical harm.

The skin barrier is designed to withstand harsh environments and must retain its ability to quickly repair, reshape, and regenerate itself over time. As the skin barrier becomes weakened due to damage, age, or stress, your body’s first line of defense against its external environment is compromised.

This puts your internal system at risk for infection, inflammation, and injury. Additionally, your body expends precious immune system resources focused on skin barrier repair rather than fending off internal damage, putting your entire system at higher risk for system-wide disorders.

Why is skin an effective barrier?

The skin is an effective barrier because of its multi-layered, highly-regulated network of cells that can withstand shearing forces and varying climates. Healthy skin can quickly and effectively regenerate, keeping your body protected even when it’s exposed to external harm. In addition, the skin helps maintain your internal water balance, temperature, vitamin synthesis, and sensation, all vital to your homeostasis and survival1.
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How does the skin function as a protective barrier?

The skin’s protective barrier functions to keep harmful environmental stressors out. The outermost layer acts as a physical barrier to keep bacteria, viruses, and other pathogens from entering your body. Other pollutants (i.e., free radicals) and ultraviolet light can directly disrupt cells at a genetic and molecular level, and the skin barrier does its best to prevent these factors from reaching and affecting those cells, especially within your vital internal organs. Additionally, the skin can balance its pH and produce surfactants, which gives it an antimicrobial defense function against invading pathogens2.

The skin also serves as a moisture barrier. The lipid barrier prevents water from evaporating from the surface of the skin. This helps to keep the body hydrated and healthy. Additionally, the natural moisturizing factor in the skin helps to attract and bind water molecules, keeping the skin strong and flexible.

Finally, the skin helps to regulate the body’s temperature. The deeper layers of the skin contain fat cells that help to insulate the body. This, along with your skin’s ability to sweat, helps to regulate the body’s temperature and protect it from varying temperatures.

What are the 3 barriers of the skin?

The skin barrier is composed of three layers that work together to form a strong barricade3:
  • Epidermis, the outermost layer: composed of dead skin cells. This layer forms a wall-like structure of dead skin cells to protect against damage and infection. This barrier is also referred to as the “moisture barrier” because of its impressive, water-retaining properties.
  • Dermis, the middle layer: composed of a network of collagen and elastin fibers. This layer helps to keep the skin strong and resilient and supports molecular and immune function. Here is where you’ll find connective tissue, hair follicles, blood vessels, and sweat glands.
  • Hypodermis, innermost layer: composed of fat cells to insulate the body and give a denser structure.

What are the 2 main functions of the skin barrier?

The two main functions of the skin barrier are to protect the body from harmful environmental factors and to retain moisture. The epidermis is composed of dead skin cells that act as a physical barrier to keep pathogens and damaging factors out of the body. Additionally, the skin has an acid mantle, which helps to maintain the skin’s pH balance and protect it from bacteria, fungi, and viruses. The lipids, fatty acids, ceramides, and hyaluronic acid in the skin form a “barrier” that prevents water from evaporating from the surface of the skin.

What is the protective barrier of the skin called?

The upper layer of the epidermis–called the stratum corneum–is your body's first line of defense. This barrier is often described as a brick wall composed of skin cells called corneocytes bound together by keratin and natural moisturizers. Without it, harmful toxins and infectious pathogens could penetrate your body and cause significant effects and disease.

What is the skin's barrier made of?

Skin is made up of a complex network of various cells, proteins, fatty acids, and lipids. Proteins serve as the building blocks of the physical skin structures and key signaling molecules for the skin’s regulation ability. Fatty acids, such as ceramides and hyaluronic acid, are chemical building blocks that help to strengthen the skin barrier and retain moisture. Lipids are a group of fats that form a barrier to keep water from evaporating from the surface of the skin. These components give the skin structure and help to attract and trap water.

The skin also has natural moisturizing factors that help to keep the skin hydrated and the barrier strong. These factors are made up of amino acids, lactic acids, and urea, which attract and bind water molecules. Additionally, the skin has an acid mantle, which is a thin protective layer of fatty acids and sebum that helps to maintain the skin’s pH balance and protect it from bacteria and other pathogens.

What causes skin barrier damage?

Many intrinsic and extrinsic factors can contribute to a damaged skin barrier.
  • Cold, dry environments can significantly contribute to a compromised skin barrier due to the rapid removal of moisture essential oils in the skin needed to maintain tissue homeostasis.4
  • Damaging or ineffective skin care and skin products can also lead to the accumulation of dirt/pollutants or over-exfoliation, which can compromise the structure and function of the skin. Additionally, skin barrier damage can be caused by certain skin care ingredients, such as parabens, fragrances, sulfates, and alcohol. These ingredients can strip the skin of its natural oils and disrupt its pH balance, resulting in a dysfunctional lipid barrier.5
  • Diet and lifestyle can also greatly affect skin function and appearance. Irregular or inadequate water intake can lead to skin dehydration. Unhealthy foods rich in trans fats can cause acne-prone and oily skin 6. Other lifestyle choices, such as smoking, alcohol intake, and stress, can increase the skin’s biological age and compromise its function7.
  • Overexposure to Ultraviolet (UV) rays can cause extensive DNA damage in our skin cells and be devastating to our body’s overall health. Stress can also provoke endocrine and immune-mediated tissue remodeling in the skin, which can alter the lipid barrier8.

How can I promote a healthy skin barrier?

Skin and longevity researchers have discovered and developed many ways to protect, reverse, and restore skin barrier function.
  • Moisturize and use sunscreen. Fortifying your skin’s lipid barrier with an effective peptide moisturizer and protecting skin from UV rays (even in the winter!9) is key to skin barrier protection.
  • Avoid smoking and engage in stress-reducing activities such as meditation and yoga, and be sure to eat healthily! Research shows that a healthy diet with whole foods and healthy fats (fish oils, antioxidants, green veggies), and avoidance of tobacco and alcohol, can truly promote younger-looking and better-functioning skin.
  • Revamp your skincare routine. Proper facial cleansing and moisturizing are key ways to preserve skin function. OneSkin has developed a scientifically validated line of skin health products powered by the OS-01 peptide: scientifically proven to increase the epidermal thickness of lab-grown ex vivo human skin models. OS-01 FACE is clinically validated to improve skin barrier function by +15% on average (trans-epidermal water loss measured via a vapometer in a 12-week clinical study performed by a third-party CRO).


  • The skin is the largest organ of our body and is responsible for protecting us from harmful environmental factors such as UV rays, bacteria, and viruses. Maintaining a healthy skin barrier is an important part of maintaining whole body health, as it helps to keep the skin, our largest organ, hydrated and protected.
  • The skin barrier is made up of several components, including lipids, fatty acids, ceramides, and hyaluronic acid. These components work together to form a strong, healthy skin barrier. The skin functions as a protective barrier in several ways, including fending off harmful environmental factors, keeping moisture in, and regulating the body’s temperature.
  • Knowing how to tell if your skin barrier is damaged is key. Skin barrier damage can be caused by a variety of factors, including environmental factors and certain skincare ingredients. Incorporating topical skin care products to nurture all the important layers of the skin, making lifestyle choices that promote healthy skin, and eating foods that strengthen our skin can all help to keep our skin barrier functioning as best as possible.


  1. https://pubmed.ncbi.nlm.nih.gov/21938268
  2. https://pubmed.ncbi.nlm.nih.gov/17008883/
  3. https://www.ncbi.nlm.nih.gov/books/NBK441980/
  4. https://oneskin.co/blogs/reference-lab/dry-flaky-skin-on-face
  5. https://www.oneskin.co/blogs/reference-lab/benefits-of-cleansing-face
  6. https://www.oneskin.co/blogs/reference-lab/what-foods-cause-acne
  7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6715121/
  8. https://pubmed.ncbi.nlm.nih.gov/26449379/
  9. https://www.oneskin.co/blogs/reference-lab/yes-you-need-sunscreen-during-winter
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