Aquaporins are proteins that reside in the cellular membrane. In response to osmotic forces, they control the passage of specific materials into and out of the cell. As reported previously in Cosmetics & Toiletries,1 one type of aquaporin in human skin is aquaporin-3 (AQP3), a pore by which water, glycerin and certain other moisturizing agents gain access to the interior of epidermal cells. The importance of moisturization for skin health and appearance means that personal care companies have a reason to be interested in the activity or presence (expression) of aquaporins, especially AQP3. As reported in the technical literature, four personal care companies have studied the world of biochemicals to discover AQP3 stimulators from three different sources: vitamins, steroids and sugar alcohols.