Ceramide 6-II is a type of ceramide that is naturally found in the stratum corneum (the uppermost layer of skin). It accounts for approximately 8.8% of the total ceramide pool in the stratum corneum. Ceramide 6-II may also be referred to as Ceramide AP on a product’s ingredient label, which represents the new INCI nomenclature for this ingredient. The “A” stands for Alpha-hydroxy fatty acid and the “P” refers to the Phytosphingosine base. Topical application of Ceramide 6-II improves the skin barrier function, which helps to keep harmful environmental irritants out and also prevent skin dehydration. Ceramide 6-II can be found in skin care products that are intended to moisturize and replenish skin.