Abstract: A method of reducing the proportion of agricultural residues (ARs), such as pesticides and herbicides, present in an essential oil, comprising the treatment of the oil with an ionic liquid that has at most limited solubility in the oil, the ionic liquid having an anion and a cation chosen from the following table: cation anion dialkylimidazolium alkylsulfate trialkylimidazolium dicyanamide dialkylpyridinium alkylsulfonate dialkylpyrrolidinium alkylphosphate thiocyanate fluoroacetate fluoroalkyl sulfonate tetrafluoroborate halide The method is particularly effect with citrus oils, especially orange oil, and it can remove most ARs, without removing essential components of the oil.