Moisturizers and Dry Skin Tips

Because there are very few sebaceous (oil) glands on the arms and legs, moisturizers are very important. Winter, dry climates, and windy climates are very hard on the skin of the body. Many body lotions incorporate sunblocks for a daily routine. This is very important for sun exposed skin.

Not every skin will be dry, there is the occlusive layer that waterproofs the skin. This is called the stratum corneum. This is essentially a fat protein sandwich, sebum that is secreted from the oil glands will also have a moisturizing effect on the skin. Moisturizers are essentially a combination of occlusive and humectants. There are a number of different skin types that require different skin care.

Oily Skin:
The moisturizers for patients with oily skin should be non-comedogenic or oil-free.

Dry Skin:
There are a small percentage of people who actually have dry skin on their face, these people will be dry on the cheeks and jawline. Many of these patients work outside in rough elements, and many of these people are over 50 years of age. For these patients a creamy moisturizer in a lotion or cream is very effective. If they do not have sensitive skin, they can wear whatever products feels good.

Dry skin is more commonly seen in lighter coloured individuals. Moisturizing should be applied to the skin after washing. It should be used when the weather is cold, small amounts of moisturizer should be applied, and it is best to have multiple applications rather than using an excessive amount at one time.

Moisturizing Of The Hands:
Moisturizers that are best used for the hands will have an oil-based silicone. This is a water repellent. It also will not allow the normal fats of the surface of the skin to be washed away. These products protect the skin even after washing the hands.

The reason for the paucity of dry skin on the face, is that there is an abundance of sebaceous glands on the face to prevent dryness. These are particularly active in young people, in men, and in many normal women. If a person is scaly in the center of the face central forehead, around the nose, and on the central chin, this may be seborrheic dermatitis. The use of a heavy moisturizer in people who have central facial dandruff (seborrheic dermatitis) could lead to acne.

Normal - Combination Skin:
Most people have oily skin on the forehead, nose, and chin (called th T-zone), and dryer skin on the cheeks and neck. When the humidity is low, it may be necessary to moisturize the face. The most prudent of patients ,male or female, will select a non-comedogenic moisturizer which contains a minimum SPF of 15 in it for daily use. There are legions of such products reasonably priced, which will prevent cancer and photoaging.

Moisturizers - Body Skin:
Often heavy moisturizers such as petrolatum Aquaphor, Cetaphil cream, Neutrogena Norwegian Formula, and other Jar or tube moisturizers are needed for dry climates. What may be appropriate for facial skin may be too thin for the arms, legs, hands, and feet.The water content of the skin varies but for the epidermis it is approximately 80%, this is the same water content as in other cells. The very surface of the skin, the stratum corneum, is made up of dead skin cells and this layer is much drier, with the water content varying between 10-30%.

The stratum corneum, when it is dry, will tend to lose its luster and produce what we know as dry skin. In normal circumstances there will be movement of water from the dermis up through the more superficial layers of the skin, the water then in turn will evaporate. Skin that has low water content will dry and fissure, this makes it more prone to both bacterial and fungal infection.

Moisturizers are designed to reduce water loss from the epidermis. These do not reverse sun damage but they do prevent further dryness. They also can protect the barrier to soot and dirt and there is a temporary feeling of smoothness when these are used. The skin may swell slightly and cause some loss of fine wrinkles. The pores may appear to be smaller because of this swelling. Moisturizing is not required for those with oily skin.

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