Vape juice is a complex mixture of various chemicals, including propylene glycol, vegetable glycerin, flavorings, and nicotine. These ingredients work together to create the vapor that users inhale. Unfortunately, some of these components can also contribute to wall staining. For example, propylene glycol has been known to leave behind a greasy film on surfaces it comes into contact with. Additionally, certain flavorings may contain dyes or other additives that can cause discoloration over time. While not all vape juices will stain walls, it's important for users to be aware of the potential risks and take steps to minimize them.