Surfactant - emulsifying

Ingredients with this function help combine water and oils into a stable mixture so that the cream, lotion or serum does not delaminate during storage and application. In fact, they work at the boundary of two immiscible phases and hold them together, forming a more homogeneous, comfortable texture. Due to this, the product is more easily distributed over the skin or hair, leaves a more even coating and helps the active and caring components to evenly get to the surface. CosIng's European base uses the emulsifying function for cosmetic ingredients, and the FDA also describes emulsions as systems where oil and water phases are combined using surfactants. (single-market-economy.ec.europa.eu)

For the skin, this means a more pleasant glide, less feeling of greasy film or, conversely, dry "tightening", depending on the formula. In hair products, such components help to make conditioners, masks and creams smoother in texture, so that they are better distributed along the length and evenly envelop the hair. In addition, emulsifying surfactants directly affect the stability, appearance and sensorics of the product: from density and creaminess to shine, softness and ease of dosing. (fda.gov)

Typical examples include Glyceryl Stearate and Polysorbate 20: both are often used in creams, lotions, and cleansing formulas where water needs to be "befriended" with oil components and maintain a stable consistency. It is important to understand that this function itself does not automatically make the ingredient irritating or, conversely, particularly useful: the result depends on the specific substance, its concentration and the entire formulation of the product. (joint-research-centre.ec.europa.eu)