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During distillation, the water-insoluble fraction, theessential oil, is separated from the soluble fraction, the hydrolat (or hydrosol). “Even if their properties are often similar, it is impossible to replace an essential oil with its hydrosol,” says pharmacist Danièle Festy. Firstly because their concentration in active ingredients is in no way comparable. Then because, unlike essential oils, hydrosols are aqueous and therefore fragile: microbes can develop there in the event of misuse or improper storage. Nevertheless, hydrosols (HA) also have interesting properties, and their great softness generally makes them much easier to use.
