First, you should know the differences between the two varieties of oils:
Fragrance oils – are made up of chemical aromas, aromatic resins and in some instances essential oils – these are mainly synthetically produced. Fragrance oils are specifically designed to be used in wax and other bases suited for making home fragrance products. They are a more cost-effective option to using in your products and a little will go a long way. You’ll find a wider variety of fragrances available due to the ability to create different scents using scientific techniques.
Essential oils – are derived from natural sources such as plants – these are natural. Many lose their therapeutic benefits when they are burned in a candle. You generally need to add a lot more essential oil to wax to achieve a strong fragrance throw. These are also typically much more expensive than fragrance oils. With essential oils, you’re limited to what fragrances you can offer.
Therefore whilst essential oils are natural and you may think they would be the best option, they are not sustainable or effective fragrances for candles. Fragrance oils however are generally safe, provide a much wider variety of fragrances, are much more cost-effective than essential oils, and produce the best-scented candles.