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.
Pentylene Glycol is a great replacement for Propylene Glycol. It has very similar characteristics but it’s derived from plants (usually from corn). Natural cosmetics lovers will find this component very useful. It enhances the moisturizing effect of cosmetic products, improves the efficiency of preservatives and it’s an effective emulsifier. It’s approved by ECOCERT and COSMOS so it’s considered to be 100% safe and can be used in vegan products.
Butylene Glycol is a very popular synthetic alcohol. It helps the product to absorb deeper and faster. It is also a solvent for other ingredients. As for the skin benefits, it helps to attract water and helps to make the skin softer.
Unlike many other “Glycols”, it is not harmful and that's why it is used in many products. It was approved by US FDA and US EPA for usage.
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.
Caffeine stimulates all the processes inside skin cells. It's very effective for reducing swelling on the face (especially great for under the eyes area). The effectiveness depends on the concentration, the more component you apply the better the effect will be.
It also tones up the skin making it look younger. It's great for dry skin because it stimulates the synthesis of cholesterol, a chemical that helps to form a protective layer on the surface of the epidermis.