Moisturizers are an important category of personal care products, and such formulas are designed to add moisture to the skin. Developing a good moisturizer requires carefully balancing the ingredients in a formula so that, upon application, the product maintains proper water content in the skin, i.e., 10–30%, to maintain its plasticity and barrier integrity. Insufficient water content can lead to the thickening or thinning of skin; fissure development, which produces chapped, rough and cracked skin; and the loss of pleasing skin aesthetics. Therefore, choosing the right moisturizer requires knowledge of its chemical, physical and performance properties and how to best utilize it against the targeted performance claims and consumer expectations. In addition, it requires knowledge of the skin to which it will be applied.
In general, skin conditioning needs can be classified based on skin health: normal, varying degrees of dry, oily, sensitive, dermatologically damaged and mature. There are other ways to classify skin types, most notably by the well-known and modified Fitzpatrick systems, all of which are more centered on the physiological health of skin and effects of sun exposure. Skin discomfort is unacceptable to consumers, thus moisturizers containing emollients and humectants are used to help alleviate the symptoms of skin discomfort. Since moisturizing lotions provide temporary relief of these symptoms, they are applied to the skin as a constant routine for skin management, to help to provide a healthy skin feeling. Following is an abbreviated explanation of the performance criteria of moisturizers, humectants and emollients.