Well…if you’re a candle maker or soap maker who uses them interchangeably – who makes candles and makes soaps that just smell good (to you and others,) regardless of whether it’s natural or not, then there’s probably not much difference at all. As long as it’s a quality fragrance or essential oil, and has been tested to be safe in the application you're using it for.
But if you’re dedicated to making only natural soaps and natural candles, then there is all the difference in the world! Few topics in soap making and candle making have engendered so much discussion, debate and controversy as fragrance oils vs. essential oils in candle and soap making.
But let’s start with the basics:
What is a fragrance oil?
A fragrance oil is a mix of various chemical components, some natural (from plants or even animals), and some synthetic. They are carefully formulated and/or blended to the exact specifications of a perfumer whose goal is to design a scent. “The perfumer is effectively an artist who is trained in depth on the concepts of fragrance aesthetics and who is capable of conveying abstract concepts and moods with their fragrance compositions.” --Wikipedia - "Perfumer" Sometimes they are formulated to smell like something occurring in nature (e.g. lavender, pine, bluebonnets, strawberries), or sometimes they are formulated to smell like an entirely new creation or concept (e.g. spring rain, love spell, winter wonderland.)
There are literally thousands of various compounds that each have their own scent…that blended together create a fragrance oil. Some fragrance oils contain essential oils as part of the natural components or constituents. Some do not. Some contain synthetically made constituents of essential oils. To help thin the various compounds, and to help create some uniformity of strength across fragrance oils, they are usually diluted with a “diluent.”
Whether the constituents of the fragrance oil are safe on your skin will determine whether or not a fragrance oil is “skin safe” for soap, lotions or other cosmetic applications. Fragrance oils, and especially the constituents that make up fragrance oils, are guided by the Research Institute for Fragrance Materials (RIFM) which generates, evaluates and distributes scientific data on the safety assessment of fragrance raw materials found in perfumes, cosmetics, shampoos, creams, detergents, air fresheners, candles and other personal and household products. Perfumers and fragrance oil blenders are also guided by IFRA, the International Fragrance Association, which is the official representative body of the fragrance industry worldwide. Its main purpose is to ensure the safety of fragrance materials through a dedicated science program. They focus on fragrance safety both as it relates to the consumer and to the environment.
The DuPont Corporation used to use “Better Living Through Chemistry” as their slogan. Think of fragrance oils as “Better smelling through chemistry.” Just like chemistry has created many wonderful and safe things that make our world better, easier and more pleasant - chemistry has created many wonderful-smelling things that are a part of our everyday lives.
However, not everyone believes in "Better Living Through Chemistry"...especially as it relates to chemicals in our soaps and candles. What if you want it natural?