Dimethicone, a pure a synthetic silicone, is one of the most frequently used emollient ingredients in moisturizers due to its gentleness and effectiveness. Dimethicone is considered a synthetic ingredient, even though it’s derived from natural silicon. Contrary to popular belief silicones are non-comedogenic and non-sensitizing. Dimethicone is considered safe as used in cosmetic products.

Applied to skin, dimethicone forms an occlusive permeable barrier that works to prevent moisture loss and impart a wonderfully silky feel.When applied to the skin, its known for creating a subtle gloss that feels smooth and silky to touch. It also acts a mild water repellent by forming a protective barrier on the skin, and can fill in fine lines/wrinkles on the face, giving it a temporary “plump” look.

Dimethicone (Wikipedia)

Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, as its versatility and properties lead to many applications.

Polydimethylsiloxane

Names
IUPAC name poly(dimethylsiloxane)
Other names PDMS dimethicone dimethylpolysiloxane E900
Identifiers
CAS Number	9006-65-9 Y
3D model (JSmol)	n = 12: Interactive image
ChemSpider	None
ECHA InfoCard	100.126.442
E number	E900 (glazing agents, ...)
UNII	92RU3N3Y1O Y
CompTox Dashboard (EPA)	DTXSID0049573
SMILES n = 12: C[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)C
Properties
Chemical formula	CH3[Si(CH3)2O]nSi(CH3)3
Density	0.965 g/cm3
Melting point	N/A, vitrifies
Boiling point	N/A, vitrifies
Pharmacology
ATC code	P03AX05 (WHO)
Hazards
NFPA 704 (fire diamond)	1 1 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

It is particularly known for its unusual rheological (or flow) properties. PDMS is optically clear and, in general, inert, non-toxic, and non-flammable. It is one of several types of silicone oil (polymerized siloxane). Its applications range from contact lenses and medical devices to elastomers; it is also present in shampoos (as it makes hair shiny and slippery), food (antifoaming agent), caulk, lubricants and heat-resistant tiles.