Editor’s note: Complementing his regular “Anatomy of a Formula” column that explains how to build formulas from individual ingredients, Eric Abrutyn now takes a top-down approach by breaking commercial products down to examine their individual components in this new column, “Formulas Deciphered.”
Facial washes, offered either as clear liquids or opaque base creams, have been around for some time. The primary performance characteristics include: a creamy lather with some level of foam that spreads without dripping, exhibits low irritation, imparts a soft/silky after-feel, is non-drying and is easy to rinse off. In the case of facial wash, it is appropriate to reduce the surface cleaning properties so as not to strip away desirable lipids on the skin surface.
The surfactant system is the key building block to any facial wash. This system is comprised of anionic, cationic, nonionic and amphoteric surfactants. Anionic surfactants such as carboxylic acid, sulfates, sulfonic acids and phosphoric acid derivatives are incorporated for their surface activity and have negatively charged polar head groups. Cationic surfactants have positively charged polar head groups, such as amines, alkylimidazolines, alkoxylated amines and quaternary ammonium. These materials are used for their substantivity and electrostatic attractive properties to skin.
Nonionic surfactants, which have no charge, are incorporated into facial washes as emulsifiers, conditioning agents and solubiliziers/coupling agents. These surfactants have a diverse representation, including alkylene oxides, polyglucosides, fatty alcohols, ethanolamines and dimethylamine oxides. Finally, amphoteric surfactants are used in facial care washes as secondary surfactants to help boost foam, improve conditioning and reduce irritation. They are zwitterionic and can be positively or negatively charged, depending on the pH of their environment.
Besides the surfactant system, other important components in a facial wash are stabilizers such as fatty alcohols, emollients and moisturizers including glycerin, fatty acid esters and polymers, rinse-off aids, chelating agents, pH adjusters, viscosity modifiers such as salt and gums, UV stabilizers for colorants, and antioxidants.
During the past few months, a few innovative facial cleansers have been launched on the market. The most recently launched cleansers have focused on brand positioning using botanical claims or natural ingredients, refreshing cooling agents, fragrance appeal, new product forms or packaging changes. The key benefits this category must provide are: effective removal of facial oils, pleasurable experience during application, aesthetic after-feel on skin, and improved moisturization of dry skin.
Recent Facial Cleansing Patents
Following are some recently issued patents relating to the development of facial washes. These patents are highlighted for their unique approaches to this conventional product category; e.g., through antimicrobial performance, a mild and alkoxylate-free emolliency approach, anti-acne action and exfoliation.
Antimicrobial wash formulation: This invention relates to soap-based liquid body and facial wash compositions.1 In particular, it relates to such compositions comprising anti- microbial agents (e.g., silver, zinc, copper particles or mixtures thereof), and to a method for enhancing the deposition of these antimicrobial agents. Specifically, using high solvent/low water compositions together with incompletely neutralized fatty acids, which helps to structure compositions, in combination with modified benefit agents including particles and oils, the deposition of the antimicrobial agents from unpredictably stable compositions is enhanced.
Water-compatible emollient: This cleansing technology relates to improved alkoxylated derivatives of glyceryl cocoate that may be used in cleansing compositions such as body washes, shampoos, liquid hand soap, facial washes, dish detergents and car wash detergents.2 The alkoxylated derivatives of glyceryl cocoate provide improved multifunctional performance properties including conditioning and skin-feel characteristics such as skin and/or hair softness and moisturization; viscosity building; emulsification including improved stability, reduced and uniform droplet size; and foaming and skin-feel properties.
Hypohalous acids for anti-acne exfoliation: This invention aims to provide topical application of an effective formulation for the treatment and/or prevention of Acne vulgaris and related skin conditions such as acne rosacea, and for the exfoliation of the skin for aesthetic effects. The formulation contains at least one active ingredient from a group of hypohalous acids including but not limited to hypochlorous acid, hypobromous acid and hypoiodious acid.
Featured Ingredient: Betaine
Betaine often is formulated into facial cleansing products as a secondary surface active agent and a skin conditioning agent. Although its primary use is as a humectant and for foaming in hard or soft water, as stated, it also is used for its anti-static, hair conditioning and viscosity-controlling properties. The global personal care market formulates with betaine primarily in face/neck care, but also includes it in shampoo, skin care and shower products. Betaine can be used as an emulsifier and thickening agent in emulsions. It also has anti-septic properties and can be used in sanitizing products.
A number of derivatives of betaine with similar properties have also enjoyed popularity in personal care formulations, such as cocoamidopropyl betaine, behenyl betaine, cetyl betaine, babassuamidopropyl betaine and coco-betaine. Derivatization of a simple betaine can improve mildness, modulate foam-boosting qualities and change the synergy with other surfactants.
Physical properties: Coco-betaine, shown in Figure 1, has a positively charged cationic functional group such as a quaternary ammonium or phosphonium cation. Therefore, coco-betaine can be considered a zwitterion.
When a cocamidopropyl constituent is attached to the coconut fatty acid, cocoamidopropyl betaine results, as shown in Figure 2. Cocamidopropyl betaine is derived from coconut oil and dimethylaminopropylamine, and its primary physical property is as a medium-strength surfactant.
Betaine is compatible with anionic, cationic and nonionic surfactant systems. It is an effective secondary surfactant used to enhance foam and viscosity. Betaine can replace cocamide DEA or MEA and has good water solubility within a wide pH range. It typically is formulated into personal care formulations at 29–33% w/w, oftentimes with 4–7% sodium chloride. Use levels of actives formulated with betaine vary based on application but are generally added at 0.5–3.0% into betain-containing formulations.
Finished Facial Cleansers
Following are two recent facial cleanser launches. The soothing facial cleanser represents a contemporary approach to mild, natural surfactants, and the overnight facial wash represents a more traditional surfactant system in a wide range of acne-cleansing products. The information presented here is taken from publicly available resources. The sample formulations provided are for illustrative purposes only and include estimated ingredient ranges to give formulators a starting point from which to build their own unique formulations.
Neutrogena Oil-free Acne Wash Redness Soothing Facial Cleanser: This cleanser, shown in Figure 3, is formulated with salicylic acid to prevent and treat acne. It also employs the company’s MicroClear brand technology, which appears to be based on a combination of menthol lactate and botanical extracts. The product claims to not over-dry skin, as it contains naturally derived moisturizing botanical extracts such as aloe and chamomile to help calm and soothe the feel of sensitive, red, acne-prone skin. The menthol lactate delivers a refreshing coolness to the skin, eliciting a “clean skin” signal. A breakdown of the ingredients featured on this product label, along with their accompanying functions and approximate concentration ranges, is shown in Table 1.
Reckitt Benckiser Clearasil Ultra Overnight Gel Face Wash: This cleanser, shown in Figure 4, is a recent launch to the Clearasil brand range of anti-acne products. It is a cleanser designed to be used before bedtime, when the skin is reportedly regenerating. This face wash is said to work visibly to help reduce the size and redness of acne spots. A more traditional anionic-nonionic surfactant system, this product is based on sodium laureth sulfate, coco-glucoside and a betaine to provide good skin cleansing and consumer-pleasing foam structure to signal mild cleansing. Salicylic acid is used as an anti-acne agent. A breakdown of the ingredients featured on this product label, along with accompanying functions and approximate concentration ranges, is shown in Table 2.
It is important for formulators to note that facial cleansing products are a mainstay category in skin care, and that the development of these formulations requires knowledge of the surfactant types needed to effectively cleanse the facial skin. The product should not leave a residue, which could denote inadequate cleansing; however, squeaky clean typically is not a target signal of clean, as it may signal the skin is too dry. Skin moisturization for this category typically is signaled by a natural softening/smoothness of the skin. The surfactant most frequently used in this category is sodium laureth sulfate, although its use appears to be decreasing, and is being replaced with naturally derived surfactants such as fatty acid glucosides and betaines. Emollients formulated into facial skin cleansers for skin softness are those with low surface tensions and high spreading coefficients, such as lactate ester, low molecular weight dimethicones (< 20 cst) and dibasic fatty acid esters.
Finally, while the present column does not address processing conditions, is important for the formulator to understand: the pH of the system, the order of addition for surfactants, effective preservative systems to minimize incompatibilities, solubilization of the surfactants, proper balance of cleansing and foam, and robustness of the preservatives. Further, UV absorbers are required for clear formulations in clear containers, and it is always helpful to include an antioxidant and chelating agent to maintain clarity of the formula and integrity of the fragrance.
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1. US Patent Application 20100098776, Soap-Based Liquid Wash Formulations with Enhanced Deposition of Antimicrobial Agents, JO Carnali, P Shah, Quang Qiu and A Lips, assigned to Conopco Inc., D/B/A Unilever (Apr 22, 2010)
2. US Patent Application 20090181873, Water Compatible Emollient For Cleansing Products, Irma Ryklin (Jul 16, 2009)
3. US Patent Application 20080014289, Vehicle and Method for Treating And Preventing Acne Vulgaris and Exfoliating The Skin Hypohalous Acid, Jianping (Jan 17, 2008)