Find an oil that contains only aromatic plant compounds, without additives or synthetic oils. Pure oils usually list the plant’s botanical name (such as Lavandula officinalis), rather than terms like “essential oil of lavender.”
True essential oils are the ones that have been changed the least by the extraction process. Choose a chemical-free essential oil that has been extracted through distillation or mechanical cold pressing.
Purchase a brand with a reputation for producing high-quality products.
Not typically. If you are using a dark oil though, it may stain.