Having designed a small range of Fragrance Oils for manufacture by a UK company the most important aspect was safety, I had dabbled with blending Essential Oils but I am not a chemist and whilst I think that I have slight knowledge of Essential Oil properties when you look at the ingredients and allergens in Essential Oils then it all becomes quite complicated. In fact working with chemicals is tricky business, even the most natural ingredients when combined can have surprising reactions as I know at my own expense but that is another story.
Fragrance Oils come in many different grades and this is where there can be some confusion. There are Fragrance Oils sold that should only ever be used fragrance as in oil burners or Pot Pourri however these are simply marketed as Fragrance Oils, they are not suitable for use in any cosmetic product or even in candles and wax melts. Unfortunately these oils are sold with very little information and as the price of them is quite low then they can be attractive, after all with rising prices of just about everything, keeping manufacture costs down is important. Research suggests that some consumers have made the mistake of purchasing such oils for use in cosmetic and wax products and when a product is described as: "For use in burners, perfume and home scent" or "For burners, home scent, aromatherapy" then it is easy to see why this error could be made. One of the products I checked out even had a bar of soap in the images, yes the details did then outline the uses for the Fragrance which didn't include for use in cosmetics or even wax but still the product title and the images are misleading and so it is easy to see how mistakes can be made.
There are Fragrance oils that are only suitable for use in wax products and are not suitable at all for use in cosmetics.
There are fragrances oil that are suitable for cosmetics but only wash on, wash off products like soap, bath bombs, shower gels, shampoo etc.
Then there are fragrance oils that are suitable for leave on products such as creams, lotions and moisturisers.
The importance here is checking that the fragrance oil that you purchase is suitable for its intended use. Regardless of what you intend to do with your finished product, even if you are only making things for your own personal use and not for retail you should check the MSDS, Ifra and Allergen data and most importantly check the manufacturers guidelines for use and stick to their usage percentages, even if you have a Safety Assessment that states that you can use a specific percentage, if the percentage supplied by the manufacturer is lower than what a safety assessment suggest then use less, if the percentage suggests that you need to use more fragrance oil than your safety assessment then stick to your safety assessment.
There are varying qualities of Fragrance Oils being manufactured, some are concentrated and the manufacturer will specify a lower percentage for use. There are also some much weaker fragrance oils on the market, the manufacturers suggestion will be a higher percentage. Some Fragrance Oils contain essential oils that are very strong and therefore if they are suitable for use in cosmetics the percentage for use will be very low, if that information is ignored and a higher percentage used for a particular product then it is a strong possibility that the final product isn't safe to use on the skin. When a soap mould or bath bomb mould is damaged you should recognise that it is probably the essential oil of fragrance oil that is responsible but where that Fragrance oil has been used an the incorrect percentage. Fragrance oils to take caution with are ones that contain orange, clove and cinnamon essential oil, the suggested usage percentage on some fragrance oils can be as low as 0.1 percent for wash on wash off products and less for leave on products, I am not aware of any Safety Assessment that has such a low percentage for Fragrance or Essential Oils, and so understanding the vast differences between the grades of Fragrance Oils on the market and respecting the manufacturers usage guidelines and they do differ greatly then you should always be working safely and manufacturing safely.
