For soapmakers, and well-informed non-soapmakers, explaining what folded essential oils are might not be hard. For others, it probably is. In fact, there are some of us at Botanie who only just learned the answer.
As a group, folded essential oils undergo extended distillation and concentration, most often through fractionating, a low-pressure “re-distillation” that isolates the chemical components of a substance in order to alter their balance. In the case of folded essential oils, the alteration is nearly always the removal of terpenes. Folding is most common with citrus oils, which are high in terpenes – the building blocks of essential oils – and can afford to lose some to fractionating.
Though folded essential oils are frowned on for aromatherapy purposes, they are valued in other circles for particular reasons. They tend to be more concentrated, stronger oils, believed by some to be purer versions of the plant or fruit they came from. Plus, the removal of terpenes in folded oils has two distinct benefits. Since they are the most volatile component of essential oils, removing terpenes extends the life of the oil, in the bottle and in the products that include them. Terpenes are also the component that makes essential oils phototoxic, or photo-sensitive, a characteristic that makes the skin increasingly vulnerable to sunlight.
What About Soap?
Phototoxicity isn’t a concern with soap, because it’s a rinse-off product and any essential oil left on the skin is too minimal to worry about. In lotions and lip balms, though (leave-on products) photoxicity can be a concern, which is why folded essential oils – with terpenes removed – are so popular for use in cosmetics. Fewer terpenes allow for essential oils to be used in skin and hair-care formulations without concern for exposure to the sun.