Before we get into how lotions have mattifying properties that fight oil, let's first look at the chemical makeup of lotions themselves. A basic lotion is typically a semi-solid emulsion; that is, it's a combination of two liquids that can't usually be put together, such as oil and water. In order to combine them, one is added to the other in droplet form. Other ingredients such as emulsifying agents and stabilizing agents are added to the substance to help it form and keep it together [source: Personal Care Products Council].
To create a lotion that controls sebum and gives the skin a mattified appearance, the product must also contain an absorbent, an ingredient that can soak up other liquids. One typical absorbent is talc, a powdered hydrous magnesium silicate. This is a clay-like substance that contains silicon, oxygen and at least one metal, and it acts as an absorbent to soak up excess water or oil on the skin. Talc is an ingredient in many color cosmetics, as it helps control shine, yet is a soft substance for the skin. Some mattifying lotions use these clay-based silicates as a key ingredient in how they control sebum.
Other mattifying lotions may contain polymers, or plastics, to help aid in sebum absorption. A polymer is a chemical compound made up of repeating structural units, and they come in a variety of structures. Silicone polymers, which have been used for decades in skin care products, add emollient, or moisturizing, factors to make the products more soothing to the skin. Silicone also helps reduce levels of stickiness and foaming within the product.
Dimethicone is one of the more common silicone polymers, and its repeating chemical unit is shaped in a linear structure. This ingredient is important for a lotion's consistency, and when it dries, it provides a protective layer or film on the skin that acts as a barrier to unwanted substances [source: WebMD].
Although silicone polymers are still used as a significant ingredient in many mattifying lotions, the development of silicone elastomers furthered the chemical capabilities of sebum-controlling products. On the next page, we'll look at how silicone elastomers transformed the oil-control industry.