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Understanding and Fighting Winter Itch
By: Ahmed Abdullah, MD
Posted: October 28, 2011, from the November 2011 issue of Skin Inc. magazine.
Between November and March, one of the most common questions faced by skin care professionals relates to the treatment of dry winter skin. After all, it’s a condition to which few who live in Northern climates are immune. In fact, according to a report from the National Health Interview Survey (NHIS), a whopping 81 million Americans claim to experience dry, itchy or scaly skin during the winter months.
Given the prevalence of the condition, also known as “winter itch,” it is imperative that skin care professionals are prepared to combat the problem. Of course, providing clients with tips to improve the symptoms of dry winter skin is vital, but to ensure the recommendations you provide are those that will make a discernible improvement in a client’s skin, it’s necessary to have a sound understanding of the cause of the condition. What’s more, by presenting your clients with the reasons why they are enduring the discomfort of winter itch, they will be more likely to diligently implement your recommendations for how to remedy it.
Physiology of the stratum corneum
To understand skin hydration, it’s necessary to look at key components of the stratum corneum—the outermost layer of the epidermis that makes skin impermeable, and protects deeper skin tissue and the body at large from bacterial invasion and other environmental aggressors.
The stratum corneum is comprised of corneocytes, which are flattened, dead skin cells; desmosomes, the proteins that hold the corneocytes together; and intercellular lipids. Under a microscope, these components appear to be arranged in a brick-and-mortar manner, with corneocytes serving as the bricks, connected by desmosomes, and lipids playing the role of mortar that surrounds and protects the corneocytes. Collectively, these components create a physical wall intended to prevent moisture loss. However, the individual roles of corneocytes and lipids are equally important.
Corneocytes are mainly composed of keratin, which holds water and gives skin its strength, along with various other compounds called natural moisturizing factors (NMFs). As humectants, NMFs not only hold water, but also attract it; thus, they are essential to the skin’s flexibility and water-holding capabilities. However, they’re water-soluble, which is why skin dries out upon extended water contact from showering, bathing, swimming and hand-washing.