A compound that changes surface tension and facilitates, among other things, washing, wetting or combining ingredients. It is sometimes called a surfactant. Different substances of this group have different properties, so the name of the category itself does not determine the gentleness of the product.
Why a surfactant can play different roles
Surface-active substance molecules have parts with different affinity for water and fats. Thanks to this, they can facilitate wetting, removing dirt, creating foam or stabilizing systems. Not all of them do it to the same extent. The amount of foam is not a simple measure of the cleaning power, and the presence of one surfactant does not describe the entire gentleness of the recipe. What matters in a product is the concentration, the list of materials, the pH and whether the preparation is rinseable.
Surfactants are classified according to their structure and properties, not one common rating of mild or strong. Also, a combination of several materials may behave differently than each material alone. For this reason, the list of names itself should not be treated as a ready result of testing the tolerance of the entire recipe.
Meaning and application
The presence of a surfactant is related to the function of the formulation and does not determine its mildness. When assessing a cleansing gel or emulsion, take into account its intended use, method of use and overall composition. A single name is not enough to create a ranking.
In practice
Check whether the cosmetic requires rinsing and what area it is intended for. Use it as directed on the label. The amount of foam is not an independent measure of cleansing quality or skin tolerance, so do not add the product just to make more foam.
Do not use body cleanser internally or assume compatibility with intimate areas. Do not dilute the product in a large supply of home mix. Changing the formula and storage may undermine the conditions provided by the manufacturer.