We offer lists of mild and harsh surfactants

I am unaware if anyone has gone through and systematically tested and ranked a wide variety of surfactants for harshness on hair (would love a reference if something like that is published), but based on what I know of their structure, I can put forth some educated guesses as to relative harshness for some of the more commonly used materials. This is not a comprehensive list, and I am glad to offer opinions on any you come across that are not on the list (as the number of materials used is very large).

Also, remember that surfactant performance is affected by temperature, pH, concentration of the surfactants in the formula, addition of moisturizers to the formula, and concentration of other materials (such as addition of salts which provide counterions that can decrease repulsion between head groups and allow more surfactants to pack into a micelle and co-surfactants that perform similarly) in the formulation, so this is a rough guideline at best.

Harsh Surfactants

  • sodium laureth, myreth, lauryl sulfate: harsh, small molecule surfactants, with very small polar head group

  • sodium coco sulfate: very slightly milder than sodium lauryl sulfate, but not much (made from coconut fatty acid and not purified, has some molecules with longer tail groups and some with shorter), similar to sodium laureth sulfate

  • ammonium lauryl and laureth sulfate: very slightly less harsh due to larger head group (ammonium)

  • sodium C14-16 Olefin sulfonate: very harsh

  • TEA lauryl sulfate: harsh, slightly less harsh than ammonium lauryl sulfate, (larger head group than sodium or ammonium versions)

  • TEA-dodecylbenzenesulfonate: irritant and can be drying if used in too high amounts in the formula

  • sodium alkylbenzene sulfonate: harsh

  • ammonium or sodium xylenesulfonate: fairly harsh

Some Gentler Surfactants

  • sodium cocyl isethionate: extremely gentle

  • cocamidopropyl betaine: mild surfactant, in part due to its zwitterionic character

  • sodium lauryl sulfoacetate: large molecule surfactant, very mild, very gentle

  • sodium cocoyl (or lauryl/lauroyl) sarcosinate: very mild

  • ethyl PEG-15 cocamine sulfate: very mild due to being a large molecule (PEG modified)

  • dioctyl sodium sulfosuccinate (also known as aerosol-OT or AOT): mild due to its branched structure

  • sodium lauryl glucose carboxylate: very mild due to its large structure

  • disodium laureth sulfosuccinate: very mild surfactant

  • Sodium methyl 2-sulfolaurate/ disodium sulfolaurate: (synonym) Sodium Methyl Cocoyl or Lauryl Taurate - mild, derived from coconut fatty acids

  • sodium cocoyl glycinate: mild

  • Pluronic and Tetronic surfactants (gentle, nonionic, biodegradable polymeric materials)

  • polyglucosides: very mild, nonionic sugar-based surfactants

  • poly decyl glucoside carboxylate: very mild non-sulfate surfactant