Yeast extract is found in some iS Clinical products and its purpose is as a symbiont to complex with other ingredients and either potentiate their activity or allow their activity in topicals. For example, SOD (superoxide dismutase) is contained in both Reparative Moisture Emulsion and Youth Intensive Crème. Within the last few years, ingredient technology has advanced to the extent that SOD was absorbable into the skin in topical form. Complexing the SOD and forming a mutually beneficial relationship (symbiosis) with the yeast has allowed this innovation.