Natural soaps have certain disadvantages—they exhibit poor hard water tolerance, leading to the formation of insoluble calcium soaps. In addition, their inherently high pH in solution is associated with harshness and a dry after-feel; this can be compensated to some extent by adding skincare ingredients, super-fatting agents, and others, but it cannot be completely alleviated.
Syndets (synthetic detergents) are mild surfactants developed for use in toilet soaps. While more costly than natural soap, they have perceivable benefits in skin mildness and elimination of calcium soaps, giving a pH close to neutral.
Essential ingredients in use today include sodium acyl isethionate and disodium lauryl sulphosuccinate; these combine the benefits of syndet mildness with relatively good processability—the latter is a significant limitation of most syndets, which do not possess the excellent phase structuring behavior of soaps.
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Other commonly used syndet ingredients include sodium lauryl (ether) sulfate, alkyl polyglucosides, sarcosinates, and coco betaines. Lever Fabergé’s ‘Dove’ moisturizing bar is the market-leading syndet worldwide and uses sodium cocoyl isethionate as the principal surfactant.