Thursday, 28 March 2013 09:37

How Sun Damage Presents in the Skin

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Although some skin breakdown occurs simply due to the passage of time, the majority of visible aging is attributed to external offenders. Up to 85 percent of all skin aging is a result of unprotected ultraviolet (UV) exposure, smoking and other preventable causes. UV rays are a clear and well-documented affront to our skin's health and youthful appearance. From a simple sunburn to dramatic dermal atrophy, sun damage is clearly something that will affect the majority of our patients, to some degree, at some point in their lives.

In order to properly council our patients of all ages about the effects and dangers of UV exposure,it is important to understand the different presentations of sun damage, how it accumulates over time, and how to protect skin and prevent further damage.

 

girlThe Anatomy of Healthy Skin

Healthy skin is comprised of a strong and well-functioning stratum corneum; a hydrated, smooth and evenly colored epidermis; and a dermis with an organized framework of structural proteins and elastic fibers. This dermal structure is referred to as the extracellular matrix (ECM): a complex infrastructure designed to support and protect the dermal cells. If protected and unexposed to sun, tobacco and other pollutants, the dermis will only degrade about 20 percent by age 80, simply due to the passage of time. The dermal structural proteins (collagen and elastin), adhesive proteins (laminins and fibronectin), and glycosaminoglycans (GAG) break down dramatically when exposed to negative external forces – primarily UV exposure, oxidative stress and the increase in matrix metalloproteinase (MMP) activity that results. A plethora of studies confirm that unnecessary sun exposure resulting in actinic damage is the number one culprit in visible aging.

More Than Meets the Eye

Unfortunately, sunburn is not uncommon. Even the most diligent of sunscreen users will eventually forget to reapply or find themselves in an unexpected time of extended UV exposure. A sunburn is simply the visible expression of the inflammation caused by UV overexposure. But think, just one tenth of the sun exposure that is required to cause that visible sunburn is enough exposure to turn on the MMP enzymes that begin to break down healthy matrix proteins, eventually leading to wrinkling and laxity. Protecting young skin from overexposure is highly important, as just one blistering sunburn increases the chances of developing skin cancer tenfold. Once the inflammation from the burn subsides, we are left with a "healthy" tan, right? No, that tan is an outward representation of our skin's attempt to protect its DNA from mutation. Younger tanners rarely see or acknowledge the accumulating damage that is occurring with each episode of tanning because it is not visible. Regardless, it is still happening and will eventually appear later in life as hyperpigmentation, wrinkling, laxity, coarse texture and enlarged pores. It can be hard to impress upon teenagers and young adults the true cause and effect of UV exposure, but it is important to educate them about the invisible damage they are inflicting on their skin that will age them more quickly and potentially lead to skin cancer.

UV-Induced Hyperpigmentation

 skin-healthy

Healthy Skin

 skin-unhealthy

Dry and Hyperpigmentation Skin

 

Initially, many seek time in the sun when they are younger to achieve the golden brown tan often depicted as healthy or beautiful. The paradigm is shifting, however, toward an acceptance of a healthy, even complexion, regardless of color. Unfortunately, old habits die hard, and many teenagers and young adults still seek out time in tanning beds and in the sun. What many do not fully understand is that even if they avoid skin cancer, the even, brown tan that they achieved in their younger years will resurface in uneven and unappealing spots as they age. Even if they begin sun avoidance and avid sunscreen use, once the damage is done, the mottled pigmentation will appear later in life.
There are multiple presentations of hyperpigmentation, but actinic damage (UV-induced hyperpigmentation) is one of the most common. This is a result of melanogenesis, the process by which melanin is generated in response to inflammation, and UV exposure significantly increases inflammation levels throughout the epidermis and dermis. Sun-induced hyperpigmentation most often appears as random, sporadic freckling that may be more prevalent on the higher, more exposed areas of the face, such as the top of the forehead or the bridge of the nose. Although treatable, we know that the visible hyperpigmentation is not the only damage done to the skin through exposure; the unwanted pigmentation is a reminder of other, less treatable damage that has already occurred.

A Wrinkle in Time

Dynamic fine lines that result from repeated facial expressions, passage of time, and gravity are normal. Deep wrinkling, on the other hand, is not a function of normal intrinsic aging and is therefore largely avoidable. Deep wrinkles are a result of UVA rays penetrating deeply into the dermis, causing the breakdown, disorganization and cross-linking of collagen. Cross-linking refers to collagen fibers that break down and reconnect to one another in a crisscross pattern. Cross-linked collagen leads to reduced support and structure, which in turn causes these avoidable deep wrinkles. Collagen and elastin are also broken down more quickly when matrix metalloproteinase (MMP) enzymes are upregulated due to UV exposure. The two MMP that break down collagen and elastin are collagenase and elastase, respectively. These MMP are increased within minutes of UV exposure, making any time spent outdoors potentially destructive to the skin. Enlarged pores are also a direct result of the dermal collagen and elastin network becoming disorganized and degenerated, resulting in reduced support to the follicle walls and allowing pores to become lax and appear larger.

Necessary Moisture

Many important processes that occur within the skin rely on water moisture to make them happen. Additionally, a lack of moisture within the skin decreases the plump, moist and youthful look most patients seek. Think of the difference between a grape and a raisin. Dehydration of the skin is common in nearly all cases of sun damage. This lack of moisture is common in patients with aging skin due to a decrease in the skin's natural moisturizing factor (NMF). Some drop in NMF levels is expected with age, but it is accelerated by UV exposure. Even the smallest disruption in NMF can significantly decrease surface moisture levels and slow cell turnover. Additionally, the MMP responsible for the degradation of hyaluronic acid, hyaluronidase, increases in response to UV exposure and free radical damage. Patients suffering from sun damage may experience a thickened, dry stratum corneum that appears flaky, dull
and rough.

An Ounce of Prevention

It is recognized that sun exposure is the worst offender in extrinsic skin aging. Because broad spectrum sunscreens can limit UV-induced skin damage and MMP production, they are, without a doubt, the most beneficial anti-aging products to add to every patient's regimen. It is important to understand the variety of ingredients available to make informed recommendations regarding the effective use of sunscreens. Sunscreens can have either chemical or physical ingredients, or a combination of both. It is critical for skin health and anti-aging benefits that the sunscreen product protects against both UVA and UVB wavelengths, as UVA rays have a longer wavelength that gives them the ability to penetrate into the dermis and breakdown the ECM. According to the FDA Final Rule of 2011, it is required that sunscreen products have a critical wavelength of at least 370 nm (the mean level must be equal to or greater than 370 nm) to be labeled as providing broad spectrum protection. This wavelength is sufficiently difficult to achieve and will ensure that sunscreen products meeting this threshold provide a significant amount of broad spectrum protection. Currently, only four of the ingredients approved by the FDA provide true broad spectrum protection when used at appropriate levels: zinc oxide, titanium dioxide, avobenzone and ecamsule. For this reason, a true broad spectrum sunscreen should include one of those four in addition to UVB-protecting ingredients. Typically, a blend of multiple ingredients is necessary to provide a cosmetically elegant and effective sunscreen product that patients will likely commit to using daily.

Stop it before it Starts

Unprotected and unnecessary UV exposure is clearly a threat to healthy skin. Robust patient education starting at a young age can help mitigate the avoidable, early aging and potential skin cancers caused by UV rays. Try to share details about how little exposure it really takes to start a cascade of long-term damage within the skin. It may just seem like an uncomfortable sunburn when you are young, but the science tells us differently. If we can change the thought process about sunscreen use by labeling it the number one most effective anti-aging product available today, we may be able to help save our patients from premature, visible aging and skin cancer in the future. Also, make sure patients know it is never too late to start protecting their skin from future UV damage. So much of what we treat in our practices is a direct result of avoidable causes.

 

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