Skin Science

Warning: Winter Dry Skin Can Lead to Itchy Skin (Winter Itch)

Cold, dry air during the winter months is the principal source of low indoor humidities that exert drying stresses on skin, which in turn increase the likelihood of dry skin— often referred to as “Winter Dry Skin”.  Dry skin may be an aggravation to deal with, but when it also results in itchy skin, or “Winter Itch” as its called, the motivation for seeking relief grows dramatically.

Dry skin (i.e., xerosis) is recognized as a leading cause of itchy skin (i.e., pruritis) among the elderly (Garibyan et al., 2013), although there are also a variety of other causes, ranging from medications to comorbidities involving kidney and liver function (Cohen et al. 2012). Consequently, as wintertime drying stresses increase, the incidence of dry skin among seniors is expected to rise as well, along with complaints of itchy skin.

Dry Skin and Itchy Skin

Long and Marks (1992) reported that the severity of itchy skin in a sample of elderly patients was directly correlated to the degree of observed skin dryness. To further examine the relationship between dry skin and pruritus, I used Google Trends to examine search trends for the terms "winter dry skin" and "winter itch" in the United States. As the graph below shows, both search terms track each other over a five-year period and their linear correlation coefficient is 0.94, where 1 equals perfect correlation or tracking. 

Winter Itch Relief

Based on the link between skin dryness and itchiness, it is reasonable to assume that increasing skin hydration (e.g., via application of a moisturizer) will reduce both skin dryness and itchy skin. Indeed, Cristaudo et al. (2015) found that the topical application of a moisturizing cream to fifty elderly patients with varying degrees of xerosis for 28 days substantially reduced their dry skin as well as itching.  But even though this particular dry-skin treatment approach for itchy skin was successful, it is important to seek personalized care from a dermatologist regarding treatment of pruritus because there are other causes for this condition.

Key Points

  • Winter dry skin and winter itch track each other as indoor drying stresses on skin change during the winter months.
  • The primary population at risk for "winter itch" consists of senior citizens due to their increased susceptibility to skin drying stressors caused by changes in skin composition with age.
  • Maintaining healthy skin hydration is an essential goal in reducing the occurrence of dry skin as well as related skin itchiness.

References

Cristaudo, A, Francesconi L, Ambrifi M, Frasca M, Cavallotti C, and Sperduti E. 2015. “Efficacy of an Emollient Dermoprotective Cream in the Treatment of Elderly Skin Affected by Xerosis.” Giornale Italiano Di Dermatologia E Venereologia : Organo Ufficiale, Societa Italiana Di Dermatologia E Sifilografia 150: 297–302.

Cohen, Kenneth R., Jerry Frank, Rebecca L. Salbu, and Igor Israel. 2012. “Pruritus in the Elderly.” Pharmacy and Therapeutics 37: 227–39.

Garibyan, Lilit, Albert S. Chiou, and Sarina B. Elmariah. 2013. “Advanced Aging Skin and Itch: Addressing an Unmet Need.” Dermatologic Therapy 26: 92–103.

Long, C. C., and R. Marks. 1992. “Stratum Corneum Changes in Patients with Senile Pruritus.” Journal of the American Academy of Dermatology 27 (4): 560–64.

 

Your skin is aging--now what?

Biochemical changes occurring in the outer layer of your skin (i.e., the stratum corneum, or SC) as you grow older degrade the skin’s barrier function as well as its ability to retain water. Consequently, you’re more apt to experience dry skin in response to decreases in relative humidity and temperature—especially during the winter months (winter dry skin). In fact, studies have shown that a significant fraction of older adults have to deal with dry skin (or even itchy dry skin).

Background

So, what are these biochemical changes that increase the risk of dry skin with age? First of all, there is a gradual reduction in skin lipids (fats) that serve as the “cement” in the spaces between the corneocytes, or the flattened, nonviable skin cells in the stratum corneum that serve as the “bricks” in the skin barrier. Lipids inhibit the transport of water from deeper skin layers to the skin surface, and hence a reduction in lipids can adversely impact skin water losses. The primary lipids in the SC are ceramides, cholesterol, and free fatty acids. Second, the corneocytes contain a mixture of water-soluble compounds referred to as the Natural Moisturizing Factor (NMF), which are very effective in binding water and are critical to the hydration of the stratum corneum. Major components of NMF include free amino acids, pyrrolidone carboxylic acid (PCA), lactates, and urea.

In healthy, hydrated skin, enzymes are able to break down the corneodesmosomes that serve as “rivets” holding the corneocytes in place. As these rivets or connectors are degraded, the corneocytes are continually lost or shed from the skin surface (a process called desquamation). Normally the skin cells that are shed from the skin’s surface are not really visible. However, when the enzymatic processes are impaired by low water content or reduced NMF levels, the corneocytes tend to clump together and become visible as flakes or what is termed “cosmetic” dry skin.

Moisturizers for dry skin that contain natural lipids and NMF

The increased risk of dry skin as you get older is attributable in part to decreases in the lipid and the Natural Moisturizing Factor content of the stratum corneum. Not surprisingly, there are over-the-counter lotions and creams that are specifically formulated to contain one or more of the organic compounds in these natural moisturizing mixtures. 

CeraVe has both a moisturizing cream and lotion that incorporate ceramide lipids for enhancing the skin’s barrier function as well as occlusive agents that reduce water loss and humectants that help hydrate skin.  

Amlactin contains lactic acid for absorbing and retaining moisture plus enhancing the exfoliation or shedding of skin cells.

Skin Saver Tips

  • Dry indoor air caused by low water vapor levels in outdoor air increases the risk of dry skin as you get older. Use the Skin Saver Alert Tool to check if the levels merit remedial measures such as moisturizing lotions and a room humidifier.

  • Use lotions and creams that contain ceramides, urea, and/or lactate that can compensate for losses in skin lipids and natural moisturizers as you age.

  • Whatever skin-care product(s) you end up using, be sure to use them on a regular basis, as this has been shown to be a crucial aspect of their effectiveness.

References

Harding, C. R., A. Watkinson, A. V. Rawlings, and I. R. Scott. 2000. “Dry Skin, Moisturization and Corneodesmolysis.” International Journal of Cosmetic Science 22: 21–52.

Lodén, Marie. 2012. “Effect of Moisturizers on Epidermal Barrier Function.” Clinics in Dermatology, Epidermal Barrier Function: Clinical Implications and Therapeutic Relevance, 30: 286–96.

 

Skin cancers, UV sunlight exposures, and Proactive Skin Care

Two key challenges in year-round skin care involve (1) dealing with dry skin caused by changes in indoor humidity and temperature (i.e., external drying stressors) and (2) managing exposures to ultraviolet (UV) radiation from the sun to reduce the risk of skin cancer as well as photoaged skin. The benefits of improved skin hydration derived from the application of moisturizing lotions and/or the operation of room humidifiers can be observed within days. In contrast, control of UV exposures includes both short-term benefits (i.e., prevention of sunburned skin) and long-term benefits (i.e., reduced skin cancer risk).

But while the motivation to avoid sunburns can be quite high, depending in part on your susceptibility to skin reddening, the motivation to prevent skin cancer years into the future may not be as strong because the benefits are uncertain. But the good news is that skin cancer prevention can be incorporated into your daily skin care practices so that you enjoy both the immediate benefits of healthy skin now as well as a reduced risk of skin cancer in the future.

Before I outline the features of an integrated skin care strategy, let’s review some background information on skin cancer.

Types of Skin Cancers

  • Basal cell carcinoma (BCC) originates in the basal cells of the epidermis, primarily in areas that are exposed to sun such as the head and neck. Although it is the most common type of skin cancer, it doesn’t usually metastasize or spread to other organs and is rarely fatal if properly treated.
  • Squamous cell carcinoma (SCC) is a skin cancer that starts in squamous cells or the flattened cells present in the outer layer of skin. This cancer is less common than BCC, but it can be more invasive if untreated and in some cases can be fatal. Skin lesions from SCC are normally found on sun-exposed areas of the body. Basal and squamous cell carcinomas are often referred to as Nonmelanoma Skin Cancers (NMSC), and they typically occur in people older than 50 years. In 2006 there were over 2 million medical treatments for these NMSCs among the US Medicare population (Rogers et al. 2010).
  • Cutaneous melanoma (CM) is the rarest of the three primary types of skin cancer, but it is the most dangerous if untreated. This cancer forms in melanocytes located in the basal layer of the epidermis.  Unlike BCC and SCC, which are concentrated on the head and neck, cutaneous melanoma is capable of developing anywhere on the body, such as on the trunk of the body and legs.

UV radiation and skin cancer

Ultraviolet radiation (UVR) reaching the earth’s surface from the sun consists of UVA (wavelengths of 315 to 400 nm) and UVB (280-315 nm) electromagnetic radiations. Ultraviolet B radiation is more energetic that UVA, but UVA penetrates deeper into the skin. Both UVA and UVB radiation have been shown to damage dermal DNA (although by different mechanisms) and can also impact the skin’s immune system (Narayanan, Saladi, and Fox 2010). Cumulative exposure to solar UVB radiation is the primary determinant of SCC, whereas BCC is a function of both cumulative and intermittent UVR exposures (e.g., sunburns)—particularly during childhood.  Cutaneous melanoma is related mainly to intermittent UVR exposures, but the relative roles of UVA and UVB are still debated (Moan et al. 2015).

Ultraviolet radiation (UVR) from the sun is grouped into two categories based on wavelength: UVA (315 to 400 nm) and UVB (280-315 nm). The biological effects of each UVR are not identical because the mechanisms of how they interact with skin tissue differ.

Ultraviolet radiation (UVR) from the sun is grouped into two categories based on wavelength: UVA (315 to 400 nm) and UVB (280-315 nm). The biological effects of each UVR are not identical because the mechanisms of how they interact with skin tissue differ.

                    

Susceptibility (Modifying Factors) to Skin Cancer

Skin pigmentation is perhaps the most important physiological factor that controls skin cancer. The melanin pigment absorbs UV radiation irradiating skin and thus serves as a natural photoprotective agent (Brenner and Hearing 2008). Epidemiological studies have consistently shown that people with light skin have a greater risk of skin cancer than those with dark skin, which is consistent with the photoprotective properties of melanin.

Skin Cancer Prevention

Research conducted in Australia has demonstrated that regular sunscreen use reduces the risk of SCC and CM, but not BCC (Iannacone, Hughes, and Green 2014).  Failure to observe a protective effect for BCC may be due to the mechanism(s) by which basal cell carcinomas are induced. For example, if UV exposures during adolescence are an important determinant of BCC risk, then UV protection later in life may be less effective, even though BCC is related to cumulative UV exposures. Nevertheless, since BCC, SCC, and CM risks are moderated by UVR exposure, on-going UVR protection is important for the maintenance of healthy skin.

Integrated Skin Care Strategy for Addressing Dry Skin and Skin Cancer Risks

The approaches for managing the risks of dry skin and skin cancers are similar because they both rely on three concepts: LEARN, MONITOR, and MANAGE. For example, as we improve our understanding of the relationships between external skin stressors together with other risk factors and skin endpoints of concern, we are better able to devise successful strategies for mitigating effects. In this regard, an essential activity is to routinely MONITOR the external stressors that impact skin and then to implement the appropriate remedial measures (i.e., MANAGE).  The two relevant measures of external skin stressors are the Dry Skin Index (DSI) and the Ultraviolet Index (UVI). The DSI represents the drying stress of indoor relative humidity and temperature on skin, whereas the UVI is a measure of the biologically-weighted exposure to UVA and UVB radiation from the sun.

Both indexes follow distinct seasonal trends, with the UVI following sunlight intensity and the DSI changes in outdoor water vapor levels. By routinely tracking these indexes and then adapting skin care responses appropriately, you will have established a lifestyle that helps ensure year-round healthy skin and decreases the risks of skin cancer as you age. Your skin-care tools will consist of (1) moisturizing lotions/creams and a room humidifier to enhance skin hydration for dealing with dry skin and (2) broad-spectrum sunscreens, protective clothing, hats, and sunglasses to reduce UVR exposures for reducing risk of skin cancer. In addition to these skin care practices, you’ll have to incorporate lifestyle changes that mean limiting time in the sun during the peak hours of 10 am to 4 pm. If you are a parent, then an added benefit of your routine skin care practices should be an increased awareness of the need for sun protection for children under your care.

Summary

  • Exposure to ultraviolet radiation from the sun is a leading cause of skin cancers, including basal cell carcinoma, squamous cell carcinoma, and cutaneous melanoma—particularly in people with light colored skin.
  • Managing the risks of skin cancers and dry skin caused by environmental skin stressors involves the same core practices, namely, monitoring the stressors and then adopting the appropriate skin-care responses.
  • Routine monitoring of the Dry Skin Index and the Ultraviolet Index represents a core practice for maintaining healthy skin throughout the year!

References

Brenner, Michaela, and Vincent J. Hearing. 2008. “The Protective Role of Melanin Against UV Damage in Human Skin.” Photochemistry and Photobiology 84: 539–49. doi:10.1111/j.1751-1097.2007.00226.x.

Iannacone, Michelle R., Maria Celia B. Hughes, and Adèle C. Green. 2014. “Effects of Sunscreen on Skin Cancer and Photoaging.” Photodermatology, Photoimmunology & Photomedicine 30: 55–61. doi:10.1111/phpp.12109.

Moan, Johan, Mantas Grigalavicius, Zivile Baturaite, Arne Dahlback, and Asta Juzeniene. 2015. “The Relationship between UV Exposure and Incidence of Skin Cancer.” Photodermatology, Photoimmunology & Photomedicine 31: 26–35. doi:10.1111/phpp.12139.

Narayanan, Deevya L., Rao N. Saladi, and Joshua L. Fox. 2010. “Review: Ultraviolet Radiation and Skin Cancer.” International Journal of Dermatology 49: 978–86. doi:10.1111/j.1365-4632.2010.04474.x.

Rogers HW, Weinstock MA, Harris AR, and et al. 2010. “Incidence Estimate of Nonmelanoma Skin Cancer in the United States, 2006.” Archives of Dermatology 146: 283–87. doi:10.1001/archdermatol.2010.19.

The Stratum Corneum: Protector of Your Internal Organs

Layers of skin, click to expand.

Curious to learn more about the layers of skin?

Want to know what the epidermis function – the epidermis is the outermost layer of the skin – is all about? Scientist, David Layton, takes a look at one of the integumentary system’s most important components: the stratum corneum.

The outer or top layer of skin, known as the stratum corneum, provides an essential physical barrier between external environmental agents such as harmful chemicals and microbes and our internal organs. It also controls the loss of body water through the epidermis to ambient air. The barrier function of the stratum corneum (SC for short) depends on a complex combination of skin structure plus biomechanical and biochemical processes. Key components of the SC are corneocytes, which are flat, non-viable cells with protein and lipid envelopes. The extracellular matrix between the corneocytes contains lipids (fats) arranged in lamellar, sheet-like structures or bilayers. In simple terms, the corneocyte and lipid matrix is often described as a “brick and mortar” construct, with the corneocytes representing the bricks and the lipids the mortar. Each strata, or layer, works together to form the stratum corneum. Cohesion of the corneocytes is facilitated by protein structures called corneodesmosomes that connect adjacent corneocytes.

Normal Functioning for Healthy Skin

New skin cells are constantly being produced, while at the same time corneocytes are simultaneously released from the skin surface to create a healthy, homeostatic balance. An important aspect of the normal shedding of corneocytes is the gradual degradation of near-surface corneodesmosomes via enzymatic processes. Weakened corneodesmosomes, which hold corneocytes together, facilitate their release to the exterior environment. Because corneocytes are very small, their discharge from the skin surface is not even noticeable. Nevertheless, it may come as surprise to know that shed skin cells are an important component of the organic matter content of indoor dust!

Proper functioning of the stratum corneum is maintained by the hydration properties of the SC, which primarily involve (1) the transport of water from within the deeper layers of the skin to the surface and (2) retention of water. The corneocytes contain a mixture of hydroscopic (water loving) compounds collectively referred to as the Natural Moisturizing Factor (or NMF) that absorb free or unbound water to maintain skin hydration. The lipid matrix in turn serves as a semipermeable membrane that helps control the transport of water from the hydrated inner skin layers to the exterior environment. The major lipids include ceramides, fatty acids, and cholesterol.

Dry Skin Formation (Xerosis)

The proximate cause of “cosmetic” dry skin that is manifested as visible flakes on the skin surface is the reduced action of hydrolytic enzymes in degrading the corneodesmosomes. As a result, corneocytes are released in visible clumps rather than single cells due to the continuing adherence to corneodesmosomes. A trigger event for the dry-skin process is typically low environmental humidity and temperature. Drying stresses in turn can disrupt the micro organization of the lipid matrix, which contributes to its dehydration. Changes in the level of the NMF in corneocytes can also exacerbate dry skin formation.

Dry Skin Management

Moisturizing lotions and creams on the market today contain a large variety of ingredients that can serve to inhibit the movement of epidermal water to air by forming an occlusive barrier (e.g., petrolatum) and/or absorb water (e.g., a humectant substance such as glycerin) to increase skin hydration. Diligence in monitoring the occurrence of dry skin and then proactively applying moisturizing lotions to both prevent and control skin dehydration can go a long way to restoring the healthy functioning of the stratum corneum.

Takeaways

  • A dehydrated stratum corneum can lead to dry skin formation and reduced barrier function, which can subsequently increase the risk of harmful exposures to environmental agents and negatively affect your overall skin anatomy.
  • Proactive management in detecting dry skin conditions and then actively treating the impacted areas with moisturizing lotions and creams is the key to restoring a healthy stratum corneum. 

References

Harding, C. R., A. Watkinson, A. V. Rawlings, and I. R. Scott. “Dry Skin, Moisturization and Corneodesmolysis.” International Journal of Cosmetic Science 22, no. 1 (February 2000): 21–52. doi:10.1046/j.1467-2494.2000.00001.x.

Proksch, Ehrhardt, Johanna M. Brandner, and Jens-Michael Jensen. “The Skin: An Indispensable Barrier.” Experimental Dermatology 17, no. 12 (December 1, 2008): 1063–72. doi:10.1111/j.1600-0625.2008.00786.x.

Why you need to monitor indoor humidity and temperature for effective dry-skin care

The lack of physiological indicators of skin drying stressors along with the low sensitivity of thermal comfort to humidity means that people have no way of knowing when to use skin moisturizers or room humidifiers to prevent dry skin! Instead, millions of people simply deal with dry skin after it appears, and then delayed treatment with over-the-counter moisturizers may take longer to become effective.