Moisturizers and soaps for dry skin are a very important part of dermatology since keeping the skin moist is one of the key factors in maintaining healthy skin. Most moisturizers are composed of some formulation of oil and water, with added ingredients that may or may not help to combat dry skin. Note that moisturizers are only capable of keeping moisture from escaping out of the skin, not putting moisture back into the skin.
The most effective moisturizing agent available is petrolatum or Vaseline, which provides a coating over the skin through which water cannot escape. Unfortunately, because it is greasy, not many people like to use it. Ointments are usually like petrolatum, since most have an oily base. They are also very greasy and are usually used at bedtime rather than during the day. Moisturizing creams contain more oil than water and, as a result, are also very effective. These may also feel a little greasy, but less so than ointments or petrolatum. Lotions are the most popular moisturizer, but because they contain more water than oil, they are not as effective. Humectants are a class of moisturizers which do not contain oil. These contain glycerin, propylene glycol, urea, hyaluronic acid, glycolic acid and lactic acid. Humectants are extremely effective, and some, such as alpha-hydroxy acids, actually improve the skin's ability to retain moisture.
Ingredients that are often added to moisturizers include lanolin (from sheep's wool, it may cause an allergic reaction), vitamins, essential fatty acids, collagen, elastin, and keratin. Compounds such as collagen, elastin, and keratin may add a little to the moisturizer, but they also drive the price of the moisturizer up more than it is worth. Vitamins may be of benefit and are found in many reasonably-priced moisturizing products.
Important Tip: Apply moisturizers to damp skin. This traps more moisture in the skin.
A new treatment in the fight against dry skin is the use of topically applied lipids such as ceramides, sphingolipids, or cholesterol. These products are often applied before the regular moisturizer and work by replacing the skin's own lipid molecules that may have been lost with age or through sun exposure. Lipids are located in the outer layer of the skin and work by trapping water within the skin. When the lipid content is reduced, water in the skin evaporates quickly, resulting in dry skin. Use of lipid products can help to restore the lipid content in the skin, allowing the skin to retain water naturally.
Deodorants or antibacterial soaps can dry out the skin. If the odor-fighting capabilities of these soaps are desirable, then it is recommended that they be used only on areas such as the armpits, feet, private parts and so on.
Cleansing creams and lotions are the most useful treatments for particularly dry or sensitive skin. They leave behind a layer of oil that helps lubricate the skin much as moisturizers do, but they are only moderately effective at cleansing the skin. Mildly moisturizing soaps are probably the most useful for general use since they clean adequately without stripping the skin of its natural oils.