Introduction

The resolution of skin disease involves correct diagnosis, treatment of the acute condition, and proper skin care maintenance to prevent recurrence. Without any of these three key steps, skin health cannot be maintained. One aspect of healthy skin is the preservation of the skin barrier, consisting of protein-rich corneocytes surrounded by organized intercellular lipids (Bouwstra et al., 2001). These intercellular lipids are arranged as an orthorhombic laterally packed gel with a 13-nm periodicity lamellar phase induced by linoleate containing long-chain ceramides (Rawlings et al., 1994). The skin barrier can be damaged through acute insults, such as those inflicted by certain cleansing surfactants and some therapeutic anti-aging interventions such as topical retinoids, or through chronic insults such as the cumulative effect of photodamage. In some instances, the skin barrier is defective due to diseases such as atopic dermatitis or rosacea. This creates the need to restore skin health through careful selection of cleansers and moisturizers that supplement prescription therapy.

Discussion

Skin cleansing

Cleansing is important for the maintenance of skin health and disease prevention. The original bar soap cleansers represented a monumental improvement in public health and the spread of contagious disease. Perhaps soap, more than any medication developed to date, has improved health standards worldwide. Soap is formed by reacting fat with an alkaline material. The resulting fatty acid salt has detergent properties (Willcox and Crichton, 1989). Bar soaps were improved upon by the development of synthetic (that is, non-soap) surfactant liquid cleansers, many of which are capable of cleansing the skin without excess barrier damage (Fulmer and Kramer, 1986).

The more recent development of body washes allowed one to cleanse and moisturize the skin with one product in one step. These products contain a cleanser and petrolatum-based moisturizer, representing an emulsion within an emulsion. Petrolatum has been shown to repair barrier properties (Ghadially et al., 1992; Mao-Qiang et al., 1995) and to be delivered into the stratum corneum lipid bilayer when deposited from a body wash (Ertel et al., 2006). The surfactant emulsion removes the environmental dirt, microorganisms, and sebum from the skin surface, while the moisturizer emulsion remains suspended in the lather during the cleansing process. During rinsing, the lather becomes dilute and the moisturizer emulsion breaks, depositing petrolatum onto the skin, resulting in improved barrier layer lipid structure (Figure 1; Warner et al., 2003). This technology, thus, allows maintenance of skin health, but also minimizes surfactant-induced skin damage in eczematous disease conditions. A recent study (Draelos et al., 2004) demonstrated the additive benefit of a moisturizing body wash in addition to triamcinolone acetonide 0.1% in the treatment of mild-to-moderate body eczema (Table 1). Additionally, a high-depositing petrolatum-containing body wash was shown to improve barrier function even when compared with a regimen that included a regular body wash and a dermatologist-recommended leave-on body lotion (Figure 2; Ertel et al., 2005).

Figure 1.

Stratum corneum lipid organization in dry skin. Tape strips of environmentally dry leg skin were collected, fixed in Karnovsky's, post-fixed in 0.25% RuO₄, dehydrated, and embedded for transmission electron microscopy. (a) Transmission electron microscopy of dry skin before treatment; note that intercellular regions are filled with amorphous material with sparse Landmann units (intercellular lamellar lipid). (b) The intercellular lipid structure improves after using a moisturizing body wash, with more Landmann units visible. Dry skin appearance also improved.

Full figure and legend (54K)

Figure 2.

A high-depositing petrolatum-containing body wash (HDPCBW) improves barrier function compared to a regular body wash (RBW) followed by a dermatologist preferred petrolatum-based leave-on body lotion. Adult females (n=16) with environmentally dry leg skin underwent controlled leg washing for 21 days. TEWL measurements were taken at baseline and at day 21. TEWL, transepidermal water loss.

Full figure and legend (59K)

Table 1 - Investigator-assigned mean values for rosacea signs and symptoms after 4-week treatment with a niacinamide-containing facial moisturizer (n=46).

Full table

Skin moisturization

Moisturizers reduce transepidermal water loss, creating an environment optimal for barrier repair and maintenance of skin health (Warner and Boissy, 2000). In addition to a traditional moisturizing agent such as petrolatum, other materials are also effective, for example, occlusion with dimethicone; humectants such as panthenol and glycerol (Rawlings et al., 1995); emollients such as vitamin E; and skin-conditioning additives such as niacinamide (Bissett, 2002; Rawlings and Matts, 2005). A well-constructed therapeutic moisturizer might contain this variety of ingredients to address multiple mechanisms to improve skin moisturization and barrier.

Niacinamide is a relatively new barrier-repair ingredient. Niacinamide increases the epidermal production of skin barrier lipids, such as ceramides, and proteins (keratin, involucrin, and fillagrin) (Matts et al., 2002; Bissett et al., 2003), and has been reported to inhibit inflammatory cytokines (Ungerstedt et al., 2003). This enhances barrier function (Figure 3) and can prevent damage from surfactants and prescription agents such as retinoids, which can irritate skin and damage the barrier. For example, a niacinamide-containing moisturizing body lotion was shown to be more effective than traditional emollient and lactic acid-containing moisturizers in relieving dry skin in the treatment phase of a typical Kligman-type regression study (Rawlings and Matts, 2005). Additionally, in separate studies by Draelos et al. (2005, 2006), the barrier-enhancing properties of niacinamide applied topically, improved the signs and symptoms of rosacea (Table 1) and augmented the treatment response during topical tretinoin therapy (Table 2).

Figure 3.

Skin barrier enhancement by topical niacinamide. Adult female subjects (n=41) were treated with control versus 2% niacinamide for their forearm skin for 24 days, and TEWL was determined at the time points indicated in the graph. S indicates significance at P<0.002. TEWL, transepidermal water loss.

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Table 2 - Investigator-assessed signs of photodamage at baseline and after 8-week treatment with topical tretinoin plus a facial moisturizer with niacinamide (A) or a basic moisturizer (B) (n=50).

Full table

Summary

Cleansers and moisturizers can aid in the maintenance of skin health and the resolution of dermatologic disease. New body wash technologies have allowed skin cleansing to occur without additive barrier damage and the induction of eczematous skin disease. Skin cleansing followed by the use of a moisturizer can optimize barrier repair, resulting in better patient outcomes in dermatology. Skin research offers the promise of improved understanding of the effects of dermatologic disease or aging and new topical treatments to maintain or improve skin health.

Conflict of Interest

The author received an honorarium for consultant's services from Procter & Gamble toward preparation of this paper.

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