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.
Propylene Glycol is a useful componet with many positive effects. It’s a very good moisturizer. It helps to deliver ingredients into deeper layers of the skin. It creates a protective layer on the skin preventing water loss. The component is researched very well and doesn’t have notable side effects. It’s used even for making food.
Methylparaben is an effective preservative. It is a controversial ingredient in terms of safety. In 2006 there was a laboratory test showed that this component can increase the sun sensitivity of the skin cells. That’s why it’s a good idea to use sunscreen after you use this component.