Which surfactant allows oil and water to mix?

The correct choice, emulsifiers, refers to substances that facilitate the mixing of typically unmixable ingredients, particularly oil and water. This is essential in many cosmetic and skincare formulations, where a stable blend of oils and water is necessary for effective product performance. Emulsifiers work by reducing the surface tension between the oil and water phases, enabling them to combine into a uniform mixture known as an emulsion.

While surfactants, detergents, and foaming agents can also have roles in altering the properties of mixtures, they do not specifically prioritize the stabilization of emulsions in the same way emulsifiers do. Surfactants generally lower the surface tension of liquids but are not always effective in creating stable mixtures of oil and water, especially in the long term. Detergents serve to remove dirt and grease and can act as surfactants, but their primary function is cleaning rather than emulsification. Foaming agents produce bubbles or foam and are often included in products to enhance texture or sensory appeal but do not directly facilitate the mixing of oil and water.

This distinction is crucial in understanding how different types of ingredients interact in formulation science within esthetics.