Cutaneous Cleansers

B. L. Kuehl, PhD¹ , K. S. Fyfe, H BBA², N. H. Shear, MD, FRCPC³

¹Scientific Insights Consulting Group, Mississauga, Ontario Canada
²GlaxoSmithKline, Consumer Healthcare, Oakville, Ontario Canada
³Departments of Medicine (Divisions of Dermatology and Clinical Pharmacology), and Pharmacology, University of Toronto Medical School; and Division of Dermatology, Sunnybrook & Women’s College Health Sciences Centre, Toronto, Ontario, Canada

ABSTRACT

Skin cleansers may be an important adjunct to the regimen of those who use cosmetics, have sensitive or compromised skin, or utilize topical therapies. Cleansers emulsify dirt, oil and microorganisms on the skin surface so that they can be easily removed. During cleansing, there is a complex interaction between the cleanser, the moisture skin barrier, and skin pH. Cleansing, with water, soap or a liquid cleanser, will affect the moisture skin barrier. Soap will bring about the greatest changes to the barrier and increase skin pH. Liquid facial cleansers are gentler, effecting less disruption of the barrier, with minimal change to skin pH, and can provide people with a cleanser that is a combination of surfactant classes, moisturizers and acidic pH in order to minimize disruption to the skin barrier.
Key Words: cleansers, emulsifiers, detergents, surfactants, soaps

Skin cleansers are surface-active substances (i.e., mulsifiers/detergents/surfactants/soaps) that lower the surface tension on the skin and remove dirt, sebum, microorganisms and exfoliated corneum cells in an emulsified form. The ideal cleanser should do this without irritating, damaging or disrupting the skin and the moisture skin barrier. Water alone removes approximately 65% of oil and dirt from the skin, but is less effective at removing oils of cosmetic import and some environmental insults. Soaps are the oldest surfactants, and are chemically defined as the alkali salt of fatty acids with a pH of 9.5-10. Synthetic detergents vary in composition and surfactant types (i.e., anionic, amphoteric, cationic, non-ionic, and silicone) and pH. In modern usage, the term “soap” generally refers to any cleansing agent regardless of chemistry.¹

Skin cleansers consist of the following:
• Water
• Surfactants (to emulsify the debris)
• Moisturizers (to hydrate the skin and maintain the skin barrier)
• Binders (to stabilize the formulation)
• Lather enhancers (found in some products)
• Fillers (generally used to harden bar soaps and cleansers)
• Preservatives (to prevent the growth of microorganisms)
• Fragrance (generally used to mask the odour of surfactants)
• Dyes or pigments (found in some products)

Skin cleansing may disrupt or disturb the moisture skin barrier, affect the skin surface pH, and irritate the skin. The moisture skin barrier protects against transepidermal water loss, chemical insult and xenobiotic penetration while preserving water to moisturize and maintain the smoothness and flexibility of the skin. A compromised barrier has been correlated with psoriasis, ichthyoses, and atopic dermatitis.² Moisturizers, both emollients and humectants, within cleansers can maintain skin hydration as well as maintaining and restoring barrier function.³ Emollients impair evaporation of skin moisture by forming a film on the skin surface to impede water loss. Humectants attract and bind water, drawing it up from the dermis into the epidermis. The acid mantle of the skin plays an integral role in skin barrier function as well as regulating bacterial flora.⁴ Studies have shown that skin barrier regeneration/repair proceeds more slowly at neutral pH (7.2) than at physiological pH 5.5.⁵ Cleansers may also cause irritant or allergic contact dermatitis and this effect is enhanced if the skin barrier is compromised.

Table 1: Different forms of cleansers

Types of Cleansers

Surfactants can be utilized quite differently in personal hygiene products. They are selected for their functionality and ability to act as detergents/emulsifiers and foaming agents. Personal hygiene products include soaps, superfatted soaps, beauty bars, dermatological bars or cakes, liquid cleansers including facial liquid cleansers, antiseptic foaming solutions, antibacterial washes, and emulsions. Table 1 outlines different types of cleansers.

Soap, the most commonly used, is a combination of fats and oils (of animal or vegetable origin) and salt.¹ Soap is the simplest anionic surfactant, forming soap salts in water that emulsify whatever is on the skin surface while increasing the pH of the skin. Soap salts also provoke stratum corneum swelling and loss of natural humectants and water leaving the skin dry and the barrier compromised. Enriching soaps (superfatted soaps and beauty bars) with lanolin, sweet almond oil or glycerin helps to alleviate the drying of the skin.⁶

Dermatological bars or cakes are chemically different from soaps, and contain modified detergents to enhance their use. Weak organic acids and emollients need to be added to lower the pH of the product and reduce drying of the skin caused primarily by anionic surfactants. Liquid cleansers are complex formulations that contain a combination of surfactants including anionic, amphoteric, nonionic, and silicone. Liquid cleansers also offer anti-bacterial activity by maintaining the skin at physiological pH and by the activity of the surfactants that emulsify and encapsulate (depending on surfactant and formulation) bacteria for easy removal. One study demonstrated that, following hand cleansing, a liquid cleanser removed 85% of bacteria while a bar soap was able to remove only 65%.⁷ Other studies have shown a relationship between cutaneous surface pH, bacterial microflora and the influence of skin cleanser. Use of an acidic liquid cleanser led to a reduction in inflammatory acne lesions and the number of Propionibacterium acnes (P. acnes) on the skin.^4,8 Generally, liquid cleansers are mild, have an acidic pH, and have a high rinsibility factor.

Antiseptic foaming and antibacterial washes are used as an adjunct to acne treatment, since they contain bacteriostatic agents. When used properly, these washes may effect a reduction in P. acnes and prevent secondary infections in acne skin, but they are drying and irritating to most skin.

Effectiveness/Recent Research Findings

Surfactants cause the majority of adverse skin reactions and disrupt or disturb the moisture skin barrier as surface debris and microorganisms are removed. Anionic/sodium containing surfactants such as sodium lauryl sulphate, sodium tallowate and sodium stearate have been shown to disrupt lipids in the moisture skin barrier, as well as increase the pH of the skin by as much as 2-3 units.^9,10 Disruption and depletion of barrier lipids and an increased skin pH leads to a compromised skin barrier¹¹ leaving the skin in a negative physiologic state with an increased sensitivity to potential irritants.⁸ Other ?”entler” surfactant types, i.e., amphoteric (cocamidopropyl betaine) and nonionic (propylene glycol), have been shown to cause a range of skin and sensory irritations.^12,13

Preservatives are required in all cosmetic, especially liquid, formulations to prevent the growth and infection by microorganisms. Liquid formulations are also protected from microorganisms by being enclosed in a container, so that the bulk of the formulation remains protected from contamination, which can occur with handling. Preservatives, fragrances and dyes used in cleansers also cause irritant or allergic contact dermatitis. Parabens and formaldehyde donors (e.g., diazolidinyl urea, Quaternium-15, DMDM hydantoin) are the major classes of preservatives. Both classes have reported incidents of allergic and contact sensitivity and dermatitis.^14-16 Some compounds are more allergenic than others and cause greater numbers of reactions. One example is Quaternium-15, which is the sixth most common allergen in cosmetic products.¹⁶

Table 2: Comparison of Cosmetic Liquid Cleansers
*Cost in Canadian dollars to consumer as determined from one supplier (Shopper’s Drug Mart, Ontario, Canada)

Liquid facial cleansers are the most effective and beneficial cleansers for sensitive and compromised skin. Their formulations are complex, utilizing a combination of surfactants, moisturizers, binders and preservatives to form a product that will cause the fewest problems and the greatest benefits. Awell-designed liquid facial cleanser will use nonionic and silicone surfactants. Nonionic surfactants (e.g., polysorbate) combine low irritancy with surfactant class and pH compatibility. Silicone surfactants (e.g., dimethicone), provide both a surfactant that can penetrate follicles and crevices thereby bringing debris to the skin surface, and an emollient that softens the skin and creates a film to impede transepidermal water loss.¹⁷ Silicone surfactants also offer properties such as low irritation, and are noncomedogenic and hypoallergenic. Liquid facial cleansers should also contain a mixture of emollients and humectants to help restore the moisture skin barrier and limit the disruption caused by the surfactant. Tolerance is an issue for people with skin conditions such as rosacea, atopic dermatitis, acne vulgaris and sensitive skin. A compromised skin barrier results in their being more susceptible to the effects of topical treatments including cleansing. A liquid facial cleanser with an acidic pH, nonionic/silicone surfactants, moisturizers, and minimal skin residue (high rinsibility) offers the greatest benefits and synergy with topical or systemic therapy. Although liquid facial cleansers are formulated to be less irritating to the skin, some of its components may disrupt the skin barrier or cause contact sensitivities.

Table 2 outlines five cosmetic liquid cleansers that represent a combination of those recommended by dermatologists and those most popular with consumers in Canada. Some of these products are not available outside Canada, and one (Derma Jel®) is the in-store brand for Shopper’s Drug Mart, a nationwide drugstore chain. Most retailers in Canada have a store brand cleanser that is positioned to compete with Spectro Jel®. However, from an ingredients comparison the products are quite different.

Limitations/Adverse Effects

Liquid cleansers are the best choice for whole body cleansing, but cost can be prohibitive. Liquid facial cleansers are more expensive than soap ($2.20 to $7.50/100mL versus $1.00/bar respectively), but prices also vary widely even within the category. The greatest differences between soaps and liquid cleansers are the degree of disruption to the moisture skin barrier and the change to the skin pH. It is difficult, when reading a product label, to determine the function of each ingredient. Many ingredients have more than one function, and the packaging can also be confusing, i.e., phrases such as no preservatives, no surfactants, and fragrance free can be misleading. For example, propylene glycol is a moisturizer but also provides anti-bacterial and emulsifier activity. The term fragrance free can be used in a product if a natural ingredient (not a synthetic ingredient) is used to alter the scent of the product.

Conclusion

The choice of facial cleanser is important for people with normal skin, as well as for those people with sensitive skin and skin diseases such as atopic dermatitis, acne vulgaris. Liquid facial cleansers are the best choice for facial cleansing as they have an acidic pH, moisturizers and high rinsibility. Within the liquid cleanser category, the least irritating cleanser will contain non-ionic/silicone-based surfactants combined with moisturizers, as they will cause the least disruption to the moisture skin barrier and the normal skin flora.

References

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