Skin moisturizer ingredients can be divided into three categories: humectants, emollients and preservatives. Humectants, such as urea, glycerin and alpha hydroxy acids, help absorb moisture from the air and hold it in the skin. Emollients, such as lanolin, mineral oil and petrolatum, help fill in spaces between skin cells, lubricating and smoothing the skin. Preservatives help prevent bacteria growth in moisturizers. Other ingredients that moisturizers may contain include vitamins, minerals, plant extracts and fragrances [source: Kraft].
The emollient part of moisturizers can be oil-based or water-based. Oil-based emollients are heavier and may leave a residue on your skin, so they're best for people who have dry skin that needs intensive moisturizing. Water-based emollients, on the other hand, are lighter and less greasy, which make them ideal for people with normal, oily or acne-prone skin [source: Bruno].
If you want to avoid using moisturizers made from animal-based additives, such as animal fat, beeswax and milk protein, look for vegan or environmentally friendly skincare lines that contain synthetic moisturizers or vegetable glycerin [source: Carpenter].
Now that you understand how moisturizers keep your skin soft and smooth, read on to learn about the different types of moisturizers.