Mildness of surfactant

The mildness of surfactants on human skin, eyes, and hair, and especially on skin and eyes, is a difficult concept to define. So far, there is no uniform standard. The irritation or sensitization of mucosa by surfactants is mainly caused by three factors:

(1) Dissolution refers to the degree of dissolution of the skin's own moisturizing ingredients (such as the moisturizing factor NMF), intercellular lipids, and free amino acids and fats in the stratum corneum. Excessive dissolution of these ingredients will damage the skin oil and surface layer, reduce the skin's ability to retain water, and cause the cells to peel off into dandruff, which will cause skin tension, tingling, or dryness. What's more, in addition to the peeling effect on the cells, the surfactant also has a lytic effect on the cells. For example, SDS is a very effective lysing agent for biofilms.

(2) Penetrability refers to the ability of a surfactant to permeate the skin. This effect is considered to be one of the causes of various skin inflammations. Surfactant infiltration changes the original structural state of the skin and the compatibility between adjacent molecules, thereby causing contact dermatitis, dermatitis, causing skin irritation and even allergic reactions, causing erythema and edema on the skin. Surfactants have the most stimulating effect on skin and mucous membranes, followed by anions, and nonionic and zwitterionic types.

(3) Reactivity Refers to the role of surfactants in absorbing proteins, causing protein denaturation and changing skin pH conditions. Experiments show that the reactivity of non-ionic PEGs is low, and the reactivity of LAS and other anions is greater.