Susan Griffiths-Brophy, Erik J. Hasenoehrl, and Karl Wei Procter & Gamble Company, Mason Busines Center, Cincinnati, OH, USA Do you think that choosing a cleanser to wash your face is a simple task? You may think so, but with the myriad of specialty cleanser product forms and devices that currently exist, the choice may prove daunting. Today, more than ever, facial cleansing plays an important role in the lives of many consumers. Cleansing is not only a means to remove dead skin, dirt, sebaceous oil, and cosmetics but also a first step in the overall skin care routine, preparing skin for moisturizers, and other treatments. Facial cleansing also plays an important role, well beyond skin care, in maintaining the psychological wellbeing of women by helping to provide a ritualistic sense of renewal and rejuvenation. Dermatologists have a wide variety of cleansing technologies – ranging from water to a traditional bar of soap – at their disposal to meet the facial cleansing needs of different skin types and soil loads and can usually incorporate patient preference into selection as well. This chapter will (1) provide an overview of the many specialty facial cleanser technologies available; (2) recommend which technologies are best suited to each skin type and cleansing need; (3) provide an in‐depth understanding of substrate‐based facial cleansers; and (4) give an overview of cleansing devices, which represent newest technology available for cleansing one’s face. The earliest form of facial cleansing existed well before Homo sapiens inhabited earth. Early facial cleansing consisted primarily of a quick splash or rinse of the face with cold water. In fact, this habit can still be observed in the animal kingdom today among many primates [1]. The first recorded use of facial cleansing utilizing more than water was among the ancient Egyptians in 10,000 BC [2]. Egyptians were heavy users of makeups made from a base of metallic ores which contained natural dyes for color; this mixture was then painted onto the face. In this period, early Egyptians typically bathed and removed makeup in a river. Their cleansers consisted of animal fat mixed with lime and perfume and were similar to some of the homemade natural soaps in use today. Facial cleansing and body cleansing were done with the same soap. During the Middle Ages, the crusaders brought back soap from the Far East to Europe which was used for bathing and facial cleansing. In the early 1900s, bar soap was used to cleanse the face, and in the mid‐1950s, cold cream, an emulsified cleanser, was introduced. In the past 20 years, specialty facial cleansers have become quite mainstream, a result of an explosion in cleansing technology which has led to a multitude of high‐quality, relatively low‐cost cleansers. More recently, cleansing devices have been introduced to the consumer. Over the years, technical developments in facial cleansing have focused on three primary areas: (1) better removal of exfoliated skin, dirt, soil, excess sebaceous oil, and makeup; (2) synthetic surfactants that induce less skin barrier damage and are thus less likely to dry skin; (3) incorporation of cleansing chemistry onto cleansing cloths; and (4) introduction of cleansing devices that assist the performance of facial cleansers. Patients tend to take more care with cleaning and maintaining their face than the rest of their body. As such, consumer product companies have developed many different technologies and cleansing forms that benefit different facial skin types, cleansing rituals, and soil loads. Since there is such a broad array of cleansing forms, specialty facial cleansers (including devices) have become a very fragmented category of products which utilize more different technologies than most other cleaning applications. Although a wide range of products is available, these products share four common goals: (1) to clean skin (removing surface dirt and all makeup); (2) to provide a basic level of exfoliation; (3) to remove potentially harmful microorganisms (bacteria); and (4) to cause minimal damage to the epidermis and stratum corneum. In addition, facial cleansers are required to remove a myriad of chemicals and biological materials, ranging from the latest waterproof makeup to excess skin oils and upper layers of stratum corneum (exfoliated skin). It is well understood that the use of harsh surfactants and/or over‐washing skin can result in over‐removal or distortion of stratum corneum and intercellular lipids, which can lead to reduced skin barrier function [3]. While the wide array of facial cleanser technologies all provide basic levels of skin cleansing, they all clean skin slightly differently. The mechanisms by which cleansing is accomplished can be grouped into three main categories: (1) cleansing by chemistry; (2) cleansing by physical action; and (3) in many cases, cleansing by a combination of both chemistry and physical action. Two classes of chemicals are used in facial cleansers and are responsible for the cleaning effect: surfactants and solvents. Both of these types of chemicals interact with dirt, soil, and skin to remove unwanted material. Surfactants and solvents work via two different chemical mechanisms to effect removal of these materials. Understanding these mechanistic differences provides dermatologists with the insight needed to prescribe a cleansing regimen based on individual patient needs. Surfactants or “surface active agents” are usually organic compounds that are amphiphilic, meaning they contain both hydrophilic groups and hydrophobic groups. The combination of both hydrophilic and hydrophobic groups uniquely makes surfactants soluble in both oil and water. Surfactants work by reducing the interfacial tension (the energy that keeps water and oil separated) between oil and water by being adsorbed at the oil–water interface. Once adsorbed at the interface, cleaning surfactants assemble into a low‐energy aggregate called a micelle. Surfactant needs to be present at high enough concentration to form a micelle, a level called the “critical micelle concentration” (CMC), which is also the minimum surfactant concentration required to clean sebaceous oil, cosmetics, etc. When micelles form in water, their tails form a core that encapsulates an oil droplet, and their (ionic/polar) heads form an outer shell that maintains contact with water. This process is called emulsification. Surfactants clean skin by emulsifying oily components on the surface of skin with water. Once emulsified, the oil can be easily rinsed from skin during the postwash or rinse process. The stronger the surfactant, the more hydrophobic (oil‐based) material removed, the greater the potential skin damage due to excessive removal of naturally occurring skin lipids, and the greater the ensuing compromise of optimal skin barrier function, therefore, correct/careful formulation of these surfactants is required to ensure proper mildness. Recently marketed products show that with careful formulation very strong surfactants such as sodium laurel sulfate (SLS) can be well tolerated by skin. All surfactant‐based cleansers require water and generally include a rinsing step. They are best suited to removal of oily residue. Unfortunately, two problems have been associated with cleansing with surfactants (one real and one largely folk‐lore). First, because of their powerful cleansing action, overuse may completely eliminate the protective lipid barrier on the surface of skin, resulting in irritation and dryness. Second, consumers for years have heard negative stories regarding the alkaline (pH around 9) nature of these products. Wrongly assuming that since skin pH is about 5, washing with these high pH surfactants can lead to an increase in skin pH. Recent data suggest that that the skins natural buffering capacity is more than adequate to eliminate any unwarranted impact of the pH of these products. Classical surfactants used in facial cleansers are categorized into four primary groups: cationic, anionic, amphoteric, and nonionic. Cationic surfactants used alone are generally poorly tolerated and are now rarely used in skin care products without careful formulation into coacervate systems. Anionic surfactants, such as linear alkyl sulfates, consist of molecules with a negatively charged “head” and a long hydrophobic “tail.” Anionic surfactants are widely used because of their good lathering and detergent properties. Amphoteric (zwitterionic) surfactants, such as the betaines and alkylamino acids, are well‐tolerated and lather well, and are used in facial cleansers. Nonionic surfactants, such as polyglucosides and sorbitan esters, consist of overall uncharged molecules. They are very mild (tolerated better than anionic, cationic surfactants on skin) but do not lather particularly well. Some surfactants are harsh to the skin while others are very mild. Because of the wide variety of available surfactants, not all surfactant‐based cleansers are the same. It is important for patients to use products that best fit their skin type. Today, most cleansers use synthetic surfactants. A solvent is a liquid that dissolves a solid or another liquid into a homogeneous solution. Solvent‐based systems clean skin by dissolving natural sebaceous oil and external oils applied to skin via cosmetics and similar materials. Solvents work under the chemical premise that “like dissolves like.” Solvents can be classified broadly into two categories: polar and nonpolar. Typical nonpolar solvents used in facial cleansing, such as mineral oil or petrolatum, are from the oil family, whereas typical polar solvents used in cleansing, such as isopropyl alcohol and ethanol, are from the alcohol family. Solvent‐based cleansers are usually not used in conjunction with water; rather, they are applied and then “wiped” off with a tissue or cotton ball. Solvent‐based cleansers should be chosen carefully on the basis of cleansing need. Nonpolar solvents work well for removing oil‐based makeups and cosmetics but have little effect on water‐based formulations. Similarly, alcohol‐based systems work well on water‐based makeups. It is also important to note that alcohol‐based systems can dry skin, a benefit for younger consumers with acne‐prone skin but a potential disadvantage for older consumers and those with dry skin. On the other hand, oil‐based products can leave a greasy or oily residue, which is beneficial for consumers with dry skin, but undesirable for those with normal. However, recent studies have shown that a patient with oily skin can benefit from using an oil‐based or emollient cleanser. By using an oil to cleanse the skin, dirt, and excess oil are removed while leaving the skin conditioned. Hence, the skin is not totally void of the natural skin oils and the body does feel the need to generate excess oil. Choosing a solvent‐based cleanser based on skin type is critical. An alternative to chemical cleansing is physical cleaning of skin. Essentially physics, primarily in the form of friction, also plays an important role in cleansing. In facial cleansing, friction is generated primarily by the direct interaction of a washcloth, tissue, cotton ball, cleansing cloth, or mechanical device with the surface of skin. Friction works to help dislodge soils, as well as increase the interaction of chemical cleaning agents (surfactants and solvents) with soils. The role of friction will be covered in more detail in the section on substrate cleansers. Seven primary and popular forms of facial cleansers exist (other rarely used forms exist but are not covered in this chapter). These cleansers can be categorized as follows: lathering cleansers, emollient cleansers, milks, scrubs, toners, dry lathering cleansing cloths, and wet cleansing cloths. Each form is described in detail below. A summary of cleansers, technologies, and uses is shown in Table 14.1.
CHAPTER 14
Facial Cleansers and Cleansing Cloths
A brief history of facial cleansing
How facial cleansers work
Chemistry of cleansing
Surfactants
Solvents
Physical cleaning
Types of facial cleanser
Lathering cleansers
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