Generally, oil-free products can be divided into two groups. The first group contains strictly oil-free products, which are usually drying though there are some excellent exceptions, i.e. glycerin, propylene glycol and silicone bases which are not oils and are not drying. Usually strictly oil free products are used to complement topical acne therapy for people with acne condition that is resistant to treatment. These shall include solutions, gels as well as emulsions of oil-free ingredients. In fact, ingredients such as fatty acids, fatty alcohols, sterols, and silicones are acceptable in a strictly oil-free preparation.
The second is made up of borderline oil-free products called esters (i.e. oil-like emollients that may found in skin care products). It is good to know that, many of the ingredients that have been classified as comedogenic (i.e. products that induce open or closed comedones to form) are emollient esters. Also oil-free emulsions of emollient esters and water are kind of weak moisturizer which is best to be used by people with slightly oily to slightly dry skin.
Another thing to note is that powders are used to absorb water and oil, and many of them have been modified to be less drying and more cosmetically acceptable for people with a wider range of skin issues.