What constitutes “mild” soap?

Zoe Dianna Draelos, M.D.Mildness is a marketing term that has consumer meaning when applied to soaps.  A mild soap is considered to be less damaging to the skin, since most cleansers are irritating and drying.  The original cleansers introduced were true soaps formulated at an alkaline pH of 9-10.  Use of these cleansers alkalinized the skin, causing swelling of the stratum corneum proteins, as well as removal of the intercellular lipids.  Newer synthetic detergents, known as syndets, possessed a lower  pH of 5.5-7, closer to the natural neutral skin pH.  The reduced irritation and dryness seen with syndets is related to their reduced tendency to cause protein denaturation due to the charge density of protein-bound micelle-like surfactant aggregates.  Thus, anionic syndets, such as sodium lauryl sulfate and sodium laurate and sodium cocoyl isethionate, are milder producing less skin damage following cleansing.

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