Moisturizers are complex formulations designed to maintain the water content of the skin between 10% and 30%. Water is essential to maintain skin plasticity and barrier integrity. Skin that is water deficient, such as the thickened skin commonly present over the heels, fissures readily with trauma and is rough to the touch. Water is necessary to allow skin distensibility, a mandatory requirement in an organ that is in constant motion. Skin hydration is important to maintain an intact skin barrier, tactilely perceived as smooth, soft skin.

This article begins by reviewing the barrier function of the skin to gain an understanding of the physiologic role moisturizers play in skin barrier repair. Then, substances that are used to provide skin moisturization and how they function in this role are discussed. Specialty additives to enhance skin functioning are reviewed. Lastly, a discourse on the currently available therapeutic moisturizers and their efficacy is presented, including the incorporation of hydroxy acids and vitamins. Moisturizers are probably the one skin care product that affects the condition of skin dramatically. Proper moisturizer selection can aid in the treatment of disease, whereas poorly selected, poorly formulated products can initiate the disease process.