Combination skin occurs when oily, dry, or normal skin types are present simultaneously. It is unclear why this happens; however, the most common forms of combination skin tend to be either normal cheeks with an oily T-zone or dry cheeks with a normal T-zone. The skin generally is not dry and oily at the same time. Oily skin, however, can have areas that are dehydrated and require moisture. For normal to oily or oily skin with normal/dry-dehydrated patches, oil-free products that contain water-based humectants such as glycerin or sodium PCA are recommended. Products that contain ingredients that stimulate and/or repair the skin’s moisture retention capacity, for example glycolic or lactic acids, essential fatty acids, ceramides and/or cholesterol, are better suited for normal to dry skin types.