A Scientific Look at Moisturizers (pt.1)

Moisturizers are widely used products that are important in many dermatologic and cosmetic skin therapies. They contain varying combinations of emollients, occlusives, and humectants to achieve their beneficial effects, and there is an overwhelming number of formulations available. To develop a rational approach for prescribing moisturizers, commercially available products can be categorized on the basis of application site.

There is a vast array of moisturizers available on the market today and consumer demand for these products is growing. These products range from value brands that provide basic moisturization to luxury therapeutics with claims of anti-aging benefits. A recent US study found that moisturizers are the third most commonly recommended OTC topical skin product (13.4%) behind hydrocortisone (27.6%) and anti-infectives (23.4%).

What Are Moisturizers?

The term moisturizer is a marketing term with little or no scientific meaning. Consumers see moisturizers as actively increasing the water content of the skin. Dermatologists see moisturizers as bland oleaginous substances that are applied to the skin by rubbing. The term “moisturizer” does not necessarily imply that moisture or water is being added to the skin. Moisturizers are a key component of basic skin care especially when there is alteration of the epidermal barrier and reduced water content in the epidermis.
They are used to restore the barrier function of the epidermis, to cover tiny fissures in the skin, provide a soothing protective film, and increase the water-content of the epidermis. They may, thus, slow evaporation of the skin’s moisture, thereby maintaining hydration and improving the appearance and tactile properties of dry and aging skin. Newer products claim to have other properties such as anti-aging, skin-firming, anticellulite, and sun-protectant effects.

How Do Moisturizers Work?

For many years, epidermal water content has been known to be crucial for skin plasticity and the prevention of “dry skin”. Traditionally, moisturization was believed to inhibit transepidermal water loss (TEWL) by occlusion. Water originates in the deeper epidermal layers and moves upward to hydrate cells in the stratum corneum (SC), eventually being lost to evaporation.

The SC architecture is the most important factor in water flux and retention in the skin, and in overall level of moisturization. The four key processes for the formation and functioning of the SC are the corneocyte process, SC lipid process, natural moisturizing factor (NMF) process, and desquamation process. Corneocytes are the physical barrier of the SC and, when hydrated, contribute to elasticity. The lipid bilayers of the SC function as a moisture barrier and although they prevent the entry of many chemicals, they are the means of entry for most topically applied substances. The NMF is found within corneocytes and is a mix of hygroscopic molecules that, by helping maintain hydration in the corneocyte, keep the SC hydrated. Half of the NMF is amino acids derived from the protein filaggrin in keratinocytes, and the other half is salts, including lactates, urea, and electrolytes. Production of NMF is directly related to external humidity. In desquamation, corneodesmosomes are degraded by water-dependent hydrolytic agents. When there is low moisture in the SC, these enzymes do not work efficiently. Corneocytes accumulate on the skin surface producing the signs of dry skin, e.g., when the moisture content is less than 10%, and when there is loss of continuity of the SC.

The moisturizing treatment involves repairing the skin barrier, retaining/increasing water content, reducing TEWL, restoring the lipid barriers’ ability to attract, hold and redistribute water, and maintaining skin integrity and appearance. Moisturizers perform these functions by acting as humectants, emollients, and occlusives. Moisturizers containing collagen and other proteins, i.e., keratin and elastin, claim to rejuvenate the skin by replenishing its essential proteins but whether or not they have any effect on skin hydration is questionable. Moisturizers also act to reduce skin friction and increase skin hydration by providing water directly to the skin from their water phase and by increasing occlusion, as measured as a decrease in TEWL. Loden suggests that skin care products not only form an inert, epicutaneous layer, but that they also penetrate and influence the structure and function of the skin.

Moisturizers have little effect on the mechanical properties (i.e., distensibility, hysteresis, and elasticity) of the skin but do increase skin hydration significantly, as shown by an increased skin capacitance.10 When moisturizers are used to improve skin plasticity it is suggested that lipid-rich formulations be used.

Emollients

Emollients, which are mainly lipids and oils, hydrate and improve the appearance of the skin by contributing to skin softness, enhanced flexibility, and smoothness. The “skin slip” or lubricity of some moisturizers, contributes to consumer satisfaction and product preference. Consumers desire smooth skin following moisturizer application. Emollients serve to fill the cracks between clusters of desquamating corneocytes and are not usually occlusive unless applied heavily.

Long chain saturated fatty acids and fatty alcohols are commonly used in topical pharmaceuticals and cosmetic formulations. They exert their benefits through effects on the skin barrier, partially through improved repair, and on permeability. Examples include stearic, linoleic, linolenic, oleic, and lauric, which can be found in palm oil, coconut oil, and wool fat. A sterol-enriched fraction from canola oil reduced clinical signs of sodium lauryl sulphate (SLS)-induced irritation. Other lipids (e.g., fish oil, petrolatum, shea butter, and sunflower seed oil) had no effect on the degree of irritation. Loden and Andersson suggested that canola oil assisted the skin in supplying the damaged barrier with adequate lipids. Essential fatty acids (i.e., linoleic and alpha-linoleic acids) influence skin physiology and pathology via their effects on skin barrier functions, eicosanoid production, membrane fluidity, and cell signaling.

Next article will focus on emollients, occlusives, and humectants and what an ideal moisturizer should be….

J. N. Kraft, BSc (Hons)1 and C. W. Lynde, MD, FRCPC2
1Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
2University Health Network (Western Division) and Department of Dermatology, University of Toronto, Toronto, Ontario, Canada

Treatments for Chapped Lips

By Van Le | We have all experienced occasional chapped lips, but for those who experience this condition year-round, the pain and irritation can be frustrating.  Medically known as “cheilitis,” chapped lips can have several causes, including dehydration and excessive exposure to elements such as wind, sun, cold or dry air.  While most cases of chapped, dry lips are results of environmental factors, in some cases, they may be an indication of an underlying medical or nutritional problem.  There are several ways to prevent dry lips from escalating into a bigger health issue.

Dehydration
Chapped lips are often a sign that there is not enough water in the body for proper hydration.  The number one cause for dry lips is dehydration, therefore, it is important to drink at least eight 8-ounce glasses of water a day and avoid dehydrating fluids like caffeine and alcohol.  Also try to avoid licking your lips, since saliva dries quickly and leaves your lips even more dry.  In addition to keeping your body healthy, water keeps your lips looking moist and attractive.

Avoid extreme weather exposure
Just like our skin, our lips are exposed to external factors 24/7, but unlike our skin, our lips lack the melanin that protects the skin from sun exposure.  We moisturize our face daily to protect against dry air, put on sun block to protect your skin against harmful UV rays, but we often forget about protecting our lips against the very same elements.  Wear a lip balm that contains SPF protection and apply it several times a day when in the sun or exposed to extreme temperatures.  Use a humidifier when indoors to help get rid of dry air inside your house or room.

Use the right products
Fight the urge to hide dry, flaky lips under thick layers lip gloss, since some ingredients in these products can contribute to the problem.  Instead, choose a moisturizing lipstick that contains Vitamin E, shea butter, or macadamia nut oil, and avoid matte, ‘last-all-day’ products since they can be very drying.

Exfoliate
Buff away the dead skin on your lips with a lip exfoliator and soft toothbrush or warm washcloth.  Then, use a moisturizing lip product or simply apply honey to your lips and wash away after five minutes.  Honey is an excellent moisturizer and a common ingredient in most natural skin care products.  Exfoliate your lips at least once a week.

Herbal remedies
There are several herbal alternatives to help treat dry, chapped lips without exposing them to harsh chemicals.  Aloe vera gel has been a great remedy for inflammations, and drinking Aloe vera juice can help relief pain associated with dry lips.  Applying a zinc oxide treatment before bed can also help heal and lubricate lips.

A healthy diet
Chronic chapped lips can be a sign of vitamin deficiency, specifically Vitamin B.   Foods such as cauliflower, wholegrain cereal, and soy bean are great sources of this vitamin, and can help fight dry lips from the inside out.

Van Le is a staff writer for the CSU Daily Titan and writing intern for Vivoderm Laboratories in Los Angeles, California. She is currently pursuing a Journalism degree at California State University, Fullerton.

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