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.
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.
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.