What your skin does for you:
- Skin is the body’s primary defense system, acting as a physical and chemical barrier and shielding the internal tissues of the body from the outside environment. The skin protects internal tissues from ultraviolet radiation, free radicals, microorganisms, and other environmental hazards.
- Skin is the body’s primary regulator of temperature.
Most important in understanding skin function is understanding the epidermal permeability barrier, which plays a crucial role in your skin’s ability to perform its duties. In the past, much of the medical community believed a compromised permeability barrier was merely a symptom of skin disease. However, recent research suggests that a compromised barrier is actually a primary pathophysiological factor for many skin diseases (such as psoriasis, atopic dermatitis). This means a compromised barrier leaves you vulnerable to an array of problems.
Within the epidermis (outer skin layer) are molecules that perform these defensive duties, including:
- UV-absorbing molecules (melanin, trans-urocanic acid, Vitamin D and C metabolites)
- heat-shock proteins (keratinocytes), which support UV-barrier and thermal functions
- antimicrobial peptides and proteins (defensins and cathelicidins), which defend against invading microorganisms by inhibiting growth of various bacteria, viruses and fungi. Antimicrobial peptides also regulate inflammation.
The permeability barrier function, which impedes the transcutaneous movement of water and other important electrolytes, is the most important defensive functions for terrestrial life…
Epidermal permeability barrier function has the crucial role of maintaining skin homeostasis and the perturbation of barrier function has significant effects on overall skin quality. Recently, many studies have suggested that the defects in permeability barrier function are not secondary consequences, but critical factors for various skin diseases. Therefore, understanding the molecular basis of barrier function and its homeostatic responses can provide not only a more rational therapy of barrier-disrupted skin diseases, but also improve the specificity and efficacy of treatments for human skin with abnormal SC structure and function.*
Within the dermis (inner skin layer) are molecules that provide structural support and nutrients. These include:
- extracellular proteins (collagen) that provide structural support and elasticity to the skin.
- blood vessels, which supply nutrients to all skin layers
- immune cells (monocytes, macrophages and dermal dendrocytes) support skin’s defense system and regulate the skin’s response to injury
- subcutaneous fat cells provide further structural support, energy reserves, and assist in regulating body temperature to prevent excessive cooling/warming.
The skin faces daily challenges, including:
- Ultraviolet light, which produces free radicals and can potentially damage cells. The skin’s defense system can combat free radicals and repair proteins, but excessive exposure to UV light overwhelms the defense system and leads to permanent damage, referred to as photodamage. In order to prevent permanent damage, we should limit UV exposure and use sunscreen daily. (However, sunscreen may present other challenges to the skin. Wearing sunscreen that contains harmful chemicals can cause disruptions in the skin barrier and skin damage . Sunscreen can also cause inflammatory reactions within the skin. So choose sunscreen wisely. For more information about choosing sunscreen, click here.)
- Excessive dryness, which is usually accompanied by changes in the epidermal barrier and increased water loss. The roots of dry skin can be a number of things, including chemicals found in skin washing detergents, lack of fatty acids in the diet, or atmospheric conditions (like temperature, humidity, and air flow) that pull water from the skin and reduce barrier integrity. According to the Linus Pauling Institute at Oregon State University, “If left untreated, dry skin is often predisposed to insults from other sources, leading to cycles of cell damage and inflammation that perpetuate the condition.” It’s vital that our diet and topical skin care regime provide moisture and help maintain healthy barrier function.
- Intrinsic aging, which is a continual decrease in the support the dermis provides to the epidermis.
Ridges on the interface between the two layers are diminished, preventing the dermis from providing adequate mechanical support to the epidermis. Collagen levels are lower and extracellular proteins in the dermis are more disorganized in skin of older individuals compared to younger adults. These changes result in increased skin fragility and laxity, as well as decreased size of the dermis and reduced vascularization, which reduces nutrient availability to the skin. Aged skin keratinocytes are relatively slow to differentiate and shed, which alters their ability to maintain the stratum corneum. These changes may lead to an overall dull skin appearance and loss of protective ability of skin…
Most of intrinsic skin aging cannot be avoided. The cumulative effects of decades of skin wear cannot be reversed, although the effects on skin appearance may be temporarily masked. Aging skin has a diminished ability to respond to stress; therefore, skin damage from other sources can enhance the signs of skin aging. This is particularly true for ultraviolet (UV) exposures, because antioxidant capacity, immune function, and melanin production may all be impaired in aged skin. Therefore, treatments designed to attenuate damage from other sources are also important factors in limiting age-associated skin damage.**
Things we can do to help our skin flourish:
- Protect your skin! Use a non-toxic sunscreen and moisturizer daily, and be sure to reference the Skin Deep Cosmetics Database to understand potential toxins your skincare products may contain. Eat a diet filled with antioxidant-rich foods to help reduce damage caused by free radicals.
- Be sure to include essential fatty acids in your daily diet. Click here to understand how you can integrate these beneficial fats into your diet. Click here for further information the relationship between fatty acids and the skin.
- Consider including additional nutrients in your skin care regime. Click here for more information on Vitamin C and the skin. Click here for more information on Vitamin E and the skin.
Sources
*Hun Lee, Seung; Kyoo Jeong, Se; Ku Ahn, Sung. An Update of the Defensive Barrier Function of Skin. Yonsei Medical Journal. US NAtional Library of Medicine National Institutes of Health. June 30 2006. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2688147/#B66. December 20 2012.
**Michels, Alexander J, Ph.D. Micronutrients and Skin Health. Linus Pauling Institute. Oregon State University. September 2011.
