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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.
page 2 of 6
Intercellular lipids are comprised of ceramides, free fatty acids and cholesterol. In the stratum corneum, their role is to prevent the loss of NMFs from within the corneocytes. On the topmost layer of skin, they combine with sweat to form the thin acid mantle—the chemical barrier that kills bacteria and regulates moisture loss. What’s more, lipids lubricate the skin and, as such, are a major factor in ensuring smooth texture.
Environmental impact on the stratum corneum
For the stratum corneum to properly protect the body, it must be elastic and flexible, which is only possible when the skin is properly hydrated. Normal, healthy skin is 20–35% water. Each day, it loses approximately a pint of water through transepidermal water loss (TEWL), the continuous process by which water leaves the body and enters the atmosphere via evaporation and diffusion. However, when humidity drops, as it does in cold-weather months, there’s a dramatic increase in TEWL as the dry air pulls moisture from the skin. When the skin’s water content drops below 10%, it begins drying and brings discomfort characterized by redness, itchiness and flakiness. With less water in the skin, the production of NMFs becomes impaired and lipid levels fall, setting in motion a vicious cycle that is hard to remedy.
Add to the mix ongoing or prolonged exposure to irritants, such as soap and even water, and you have a far worse situation. This exposure causes the skin’s acid mantle to disintegrate, which further increases the rate of TEWL and decreases lipid levels. The result is even drier skin that may crack and even become infected.
With less water and fewer lipids to lubricate and protect it, skin no longer exfoliates properly. This is what results in the excessive buildup of dead cells on the skin’s surface, giving it an ashy appearance. It also results in an overall degradation of skin health; skin can no longer properly heal itself. In order to address the discomfort caused by these conditions, following are a variety of solutions that can be recommended by skin care professionals in order to help remedy winter itch.
Of course, the primary objective in treating dry skin is to first minimize discomfort. Lotions and moisturizers can bring temporary relief; however, contrary to popular belief, these products do not add moisture to the skin. Rather, they help to restore the barrier function of the stratum corneum and cover fissures in the skin. Moisturizers typically utilize the following categorical ingredients.