Surfactants, also known as surface-active agents, constitute a key group of auxiliary substances used in the cosmetics industry. They exhibit wetting, solubilising, emulsifying, foaming, and cleansing properties, while also improving the solubility of active ingredients. What exactly are surfactants, and what role do they play in modern cosmetic formulations?
What Are Surfactants?
According to the definition provided in European Commission Regulation 2006/257/EC, a surfactant:
“reduces the surface tension of cosmetic products and supports the even distribution of the product during application.”
Surfactants are commonly referred to as surface-active agents or tensides. Their defining characteristic is the ability to reduce surface tension between two substances (for example, water and oil), allowing ingredients that would normally be immiscible to combine effectively. This functionality is the result of their molecular structure. Surfactants typically consist of two distinct parts: a hydrophilic (water-soluble) moiety and a lipophilic (oil-soluble) moiety, enabling them to act as a “bridge” between substances with differing solubility profiles.
Types of Surfactants
Based on their electrical charge in aqueous solutions, surfactants are classified into four main categories:
- Anionic Surfactants – The most commonly used surfactants in cleansing products such as soaps, shampoos, and shower gels. At higher concentrations, they may cause skin irritation. Typical examples include Sodium Lauryl Sulfate (SLS), Sodium Dodecyl Sulfate (SDS), and Sodium Coco-Sulfate (SCS).
- Cationic Surfactants – Due to their softening, antistatic properties and strong affinity for hair fibres, cationic surfactants are primarily used in hair care products. Examples include Quaternium-23 and Cetrimonium Chloride.
- Non-ionic Surfactants – These surfactants carry no electrical charge in aqueous solutions and are generally milder than anionic and cationic surfactants. As a result, they are widely used in products designed for sensitive, dry, or irritation-prone skin. Examples include Lauryl Glucoside, Decyl Glucoside, and Cocamide DEA.
- Amphoteric Surfactants – Amphoteric surfactants can exhibit either a positive or negative charge depending on the pH of the formulation. They are commonly used alongside other surfactant types to reduce irritation potential. Examples include Cocamidopropyl Betaine, Coco-Betaine, and Disodium Cocamphodiacetate.
Applications of Surfactants in Cosmetics
In modern cosmetic formulations, surfactants perform several essential functions:
- Cleansing – As surface-active agents, surfactants readily bind to unwanted particles, facilitating the removal of dirt, impurities, and makeup residues. Anionic surfactants, such as SLS, are particularly effective due to their strong cleansing and foaming properties.
- Emulsifying – Thanks to their molecular structure and ability to reduce surface tension, surfactants play a critical role in stabilising emulsions—systems composed of naturally immiscible phases such as water and oils. Proper surfactant selection ensures uniform texture and enhances product stability and shelf life.
- Foaming – Foaming properties improve product spreadability, making it easier to distribute products such as soaps, shampoos, and shower gels across the skin and hair.
- Softening and Conditioning – Cationic surfactants bind to hair fibres, providing softening and conditioning effects in hair care products. They improve smoothness, reduce static, and facilitate easier detangling.
Currently, the cosmetics industry relies largely on synthetic surfactants, which may exhibit irritant or allergenic potential and are often poorly biodegradable. In response, biosurfactants—innovative, naturally derived surface-active agents—are gaining increasing attention.
Biosurfactants – Innovative Surface-Active Agents
With the growing demand for eco-friendly cosmetics and sustainable “green” manufacturing, biosurfactants have attracted significant interest from innovative cosmetic brands. Biosurfactants are biodegradable surface-active compounds produced by microorganisms—primarily bacteria, and less frequently fungi or yeasts—or derived from renewable raw materials. These ingredients stand out not only for their reduced environmental impact but also for their low toxicity and gentle interaction with the skin. For these reasons, biosurfactants are particularly valuable in the development of natural cosmetic formulations and products designed for sensitive user groups, such as children and the elderly.
Examples of Biosurfactants Used in Cosmetics
Biosurfactants can be divided into two main groups:
- Low-Molecular-Weight Biosurfactants – These compounds effectively reduce surface and interfacial tension. They include:
- Glycolipids – composed of a carbohydrate hydrophilic moiety and a fatty acid lipophilic chain. Depending on the sugar unit present, they are classified as rhamnolipids, sophorolipids, trehalolipids, or cellobiose lipids.
- Lipopeptides and Lipoproteins – consisting of a peptide-based hydrophilic segment and a lipid lipophilic chain. Notable examples include surfactin, viscosin, fengycin, and lichenysin C.
- High-Molecular-Weight Biosurfactants – Primarily used as emulsion stabilisers. This group of polymeric surfactants includes compounds such as emulsan, biodispersan, alasan, and liposan.
Literature:
- Lukic M, Pantelic I, Savic S. An Overview of Novel Surfactants for Formulation of Cosmetics with Certain Emphasis on Acidic Active Substances. Tenside Surfactants Detergents, 2016; 53(1): 7-19.
- Moldes AB, Rodríguez-López L, Rincón-Fontán M i wsp. Synthetic and Bio-Derived Surfactants Versus Microbial Biosurfactants in the Cosmetic Industry: An Overview. International Journal of Molecular Sciences. 2021; 22(5): 2371.
- Musiał C. Rola i zastosowanie glikozaminoglikawnów w trychologii i kosmetologii. Aesthetic Cosmetology and Medicine 2021; 10(1): 33-37.
- Stępieniowska A. Biosurfaktanty w kosmetykach [w:] Chwil M, Denisow B. Wybrane aspekty biokosmetologii. Wydawnictwo Uniwersytetu Przyrodniczego w Lublinie, Lublin 2021.
