Moisturizers can be grouped into several broad categories: those for a specific skin type, those designed for day or night, those that offer added benefits and those designed for specific parts of your body. All moisturizers provide a temporary barrier that protects the stratum corneum, or the top layer of skin, allowing it to repair itself. The stratum corneum is 30 percent water, so maintaining that level is important for healthy-looking skin [source: Schwartz].
Many moisturizers contain humectants and emollients. Humectants draw water from the air to your skin and help keep it there. This works well if you live in a very humid climate, but is not as effective in dry weather. Urea, glycerin and alpha hydroxy acids are examples of humectants.
Emollients sink into the spaces between skins cells where they help replace lipids, or fats, which make skin look healthier. Emollients are oils from plants, minerals or animals. Shea butter, cocoa butter, petrolatum, cholesterol and silicones are all emollients. Water-based moisturizers (which contain smaller amounts of oil dissolved in water) are lighter and non-greasy, but don't last as long as oil-based moisturizers [source: Mayo Clinic].
Moisturizers for oily skin are oil-free, for obvious reasons. Formulations for dry skin, on the other hand, specifically contain oil-based ingredients such as petrolatum. Products for sensitive skin may be free of preservatives, dyes, scents or lanolin -- the worst offenders for causing irritation. Night creams are heavier than day creams to give you eight-hour protection.
Body lotion may seem similar to face lotion, but there are some key differences. If you run out of body lotion, it's fine to use your face cream on other areas, but the opposite isn't necessarily true. Body lotions may not be formulated to use near your eyes, and lotions designed specifically for trouble spots like elbows are often too heavy for your face.
Finally, moisturizers may have various additional ingredients that offer more potential benefits, such as vitamins, minerals and plant extracts. For daytime use, it may be wise to select a moisturizer that includes sunscreen.
With all these ingredient options, you need to consider what your personal needs are before making a purchase. Read on to learn how to determine your skin type and choose a product that fits it best.