Fragrance oils, also known as aroma oils, aromatic oils, and flavor oils, are blended synthetic aroma compounds or natural essential oils that are diluted with a carrier like propylene glycol, vegetable oil, or mineral oil.
Fragrance oils are created in a laboratory. One of the main benefits is that they are non-volatile and generally last longer than essential oils.
Not all plants produce essential oils that can be used for scents. Top of mind examples include apples and blueberries. This is because most essential oils are produced via steam or water distillation (though citrus oils are often cold pressed), and neither processes effectively extract oils from apples or blueberries. Note that there is alot of marketing out there for blueberry seed oil, created by cold pressing blueberry seeds, but that is not blueberry essential oil!
Most fragrance oils don’t provide the same health benefits as essential oils, as they’re designed purely for the purpose of mimicking a scent. Nature is complex and essential oils are made of more than just scent components, which is why they are so difficult to recreate. When we isolate only the natural aromatic components from a plant, we miss out on the potential benefits the plant could offer. However, fragrance oils do enhance the aroma of many cosmetics and perfume products, as well as candles (they hold a better scent in hot temperatures).
They last much longer, because they are diluted with another oil made from dipropylene glycol (DPG). DPG is a common carrier oil used to cut fragrance oils to make them more effective.