Aromatherapy can be considered a branch of phytotherapy that uses essential oils, i.e. the volatile and strongly smelling substances of plants. The oils are usually extracted by steam distillation, which once cooled allows the separation of the essential oil from water; in the case of the epicarp of fruits of the genus Citrus cold pressing is also used. Aromatic substances extracted by other methods (extraction with organic solvents, extraction with supercritical fluids) are not considered by all authors as essential oils.
The so-called essential oils obtained by dissolving resins and oleoresins in alcohols are actually defined as resinoids.
Essential oils are contained in specific structures within various organs of the plant. In some cases only some organs are rich in them, in others all organs have significant percentages of essential oil, in many cases the composition of essential oils in different organs of the same plant has different composition. Among the organs from which essential oils can be obtained are: leaves, flowers, petals, bark, wood, seeds, pericarp, roots.
The term aromatherapy does not exclusively identify the olfactory use of essential oils, but includes all applications: topical (massages, wraps, pure applications), inhalation and oral.
A general definition of Aromatherapy could be this: the use of essential oils for the maintenance of health or for therapy.
For these reasons, and due to the scarcity of clinical data, aromatherapy is far from being defined as a real therapy, with a corpus of canonical texts, recognized modalities, standardized curricula, etc., even if the materials used by the therapy and some of the modalities of use have been subjected to clinical and pharmacological studies.