Substances

Some of the most commonly used silicone substances, called cyclosiloxanes, are:

Octamethylcyclotetrasiloxane (D4)
Octamethylcyclotetrasiloxane (D4) is an odorless, colorless non-oily volatile silicone fluid used primarily to make other silicone materials. During this manufacturing process, virtually all of the material is consumed, with only a tiny amount of D4 remaining. In a small handful of personal care products, D4 can be used as an additive, providing certain application-related benefits preferred by consumers.

Decamethylcyclopentasiloxane (D5)
Decamethylcyclopentasiloxane (D5) is an odorless, colorless non-oily volatile siloxane fluid used primarily to make other silicone materials. It is also used as an ingredient in personal care and consumer products and in dry cleaning. In personal care products, D5 acts as a "carrier," allowing products to spread smoothly and easily, providing a silky, luxurious feel during application. In dry cleaning, D5 carries detergent to clothes and rinses away suspended dirt and oils trapped by the detergent. It does not interact with textiles and therefore, helps maintain the quality and color of clothes that are dry cleaned.

Dodecamethylcyclohexasiloxane (D6)
Dodecamethylcyclohexasiloxane (D6) is a clear, odorless, siloxane fluid that is used in some applications including cosmetics, where it provides certain application-related benefits preferred by customers. 

These substances are basic members of the silicone family, serving as the building blocks for many silicones. They are used to create a diverse range of silicone materials, called polymers, that provide beneficial characteristics to a wide variety of applications and products. D4, D5, and D6 are most frequently used as raw materials, meaning that the substance is employed in the manufacturing process but is only present at very low levels in the end products.

D4, D5, and D6 are some of the most extensively studied chemicals used in consumer applications. The data generated from studies assessing D4, D5, and D6 support their safety when the products in which they are a component are used as intended.