By having a Silicon layer on top of skin, the moisture is prevented from escaping, thus helping keep skin moisturized.
Silicon is a chemically derived product with occlusive qualities. What this means in terms of skincare is that it covers the skin to protect and keep the moisture in. By doing so, Silicon also fills in uneven skin texture like fine lines and acne scars so it gives the illusion of great skin when foundation is applied over it. The molecules in Silicon are too large to penetrate into skin layers and only sit on top of the skin. By having this layer on top of skin, the skin moisture is prevented from escaping, thus helping keep skin moisturized. it is also better for those with sensitive skin due to this occlusive nature. It does not irritate skin nor does it cause acne.