Alcohol form of the B vitamin pantothenic acid. Panthenol is used in skincare products as a humectant because of its ability to attract and hold moisture. Sometimes called pro-vitamin B5, panthenol mixes readily with many different types of ingredients, making it a versatile ingredient to be used in formulas because it improves the look and feel of skin.
References for this information:
Journal of Cosmetic Science, July-August 2011, issue 4, pages 361-370