Surfactants are substances with a highly unique chemical structure and are widely used in the cosmetics industry. They serve as auxiliary ingredients in cosmetic formulations—though used in small quantities, they play a significant role. Surfactants are found in most products, including facial cleansers, moisturizing lotions, skin creams, shampoos, conditioners, and toothpaste. Their functions in cosmetics are diverse, primarily including emulsification, cleansing, foaming, solubilization, antibacterial action, antistatic effects, and dispersion. Below, we detail their four main roles:
(1) Emulsification
What is emulsification? As we know, the creams and lotions we commonly use in skincare contain both oily components and a large amount of water—they are mixtures of oil and water. Yet, why can’t we see the oil droplets or seeping water with the naked eye? This is because they form a highly uniform dispersed system: the oily components are evenly distributed as tiny droplets in water, or water is evenly dispersed as tiny droplets in oil. The former is called an oil-in-water(O/W) emulsion, while the latter is a water-in-oil(W/O) emulsion. Cosmetics of this type are known as emulsion-based cosmetics, the most common variety.
Under normal circumstances, oil and water are immiscible. Once stirring stops, they separate into layers, failing to form a stable, uniform dispersion. However, in creams and lotions (emulsion-based products), the oily and aqueous components can form a well-mixed, uniform dispersion thanks to the addition of surfactants. The unique structure of surfactants allows these immiscible substances to blend uniformly, creating a relatively stable dispersion system—namely, an emulsion. This function of surfactants is called emulsification, and the surfactants that perform this role are termed emulsifiers. Thus, surfactants are present in the creams and lotions we use daily.
(2) Cleansing and Foaming
Some surfactants exhibit excellent cleansing and foaming properties. Soap, a well-known example, is a commonly used type of surfactant. Bath soaps and bar soaps rely on their soap components (surfactants) to achieve cleaning and foaming effects. Some facial cleansers also use soap components for cleansing. However, soap has strong cleaning power, which can strip the skin of its natural oils and may be slightly irritating, making it unsuitable for dry or sensitive skin.
Additionally, bath gels, shampoos, hand washes, and toothpaste all rely on surfactants for their cleansing and foaming actions.
(3) Solubilization
Surfactants can increase the solubility of substances that are insoluble or poorly soluble in water, allowing them to dissolve completely and form a transparent solution. This function is called solubilization, and the surfactants that perform it are known as solubilizers.
For example, if we want to add a highly moisturizing oily component to a clear toner, the oil won’t dissolve in water but will instead float as tiny droplets on the surface. By leveraging the solubilizing effect of surfactants, we can incorporate the oil into the toner, resulting in a clear, transparent appearance. However, it’s important to note that the amount of oil that can be dissolved via solubilization is limited—larger quantities are difficult to fully dissolve in water. Therefore, as the oil content increases, the amount of surfactant must also rise to emulsify the oil and water. This is why some toners appear opaque or milky white: they contain a higher proportion of moisturizing oils, which the surfactants emulsify with water.
Post time: Nov-11-2025