Water is a great solvent. It’s neutral and doesn’t provide any strong positive or negative effects. It just helps components to mix better and to transport active components.
Betaine is used a lot in “organic” skincare products. It is a good moisturizer that not only hydrates the skin but also strengthens the cell membrane. This helps to lower the water loss over time. It also softens the skin and reduces irritation and redness. It’s often used at a 3-5% concentration depending on the product.
Propanediol is a good solvent, emollient and humectant. It helps to moisturize the skin and prevent moisture loss. In haircare products, it conditions hair and improves absorption of the product.
Cyclopentasiloxane is a fluid silicone. It’s non-greasy and doesn’t have any scent or color. It evaporates pretty fast which makes this ingredient essential when it comes to making products that have to dry quickly. It also gives a nice silky feeling when you apply the product to the skin and hair. It leaves a thin film that protects the skin after evaporation.
Cyclopentasiloxane is chemically neutral, meaning it doesn’t react with other components.