Aromatherapy is a pleasant way to help prevent the occurrence of, or modify the onset and course of respiratory complaints. People commonly, but anecdotally, reach to any Eucalyptus essential oil (EO) for upper & lower respiratory infections, cough, rhinitis, and sinusitis etc. But with a better understanding of the chemistry of the various Eucalyptus species, one can use each appropriately, and blend them for better clinical outcomes.
According to Chinese herbal theory, Eucalyptus in general has a pungent flavor, and an ascending neutral to cool thermal nature. Thus it is best used to release exterior wind-heat & phlegm pathogens (not wind-cold pathogens, or wind cold deficiency syndrome). Eucalytptus also benefits damp-heat in the lower burner (e.g. urogenital infections) due to its tropism with the Lung, Bladder, and Heart.
The Therapeutics of Eucalyptus by Species
There are hundreds of eucalyptus species; only a handful are used in clinical aromatherapy for their known therapeutic properties (mucolytic, antiseptic, anti infectious, anti-inflammatory, sedating ect).
... E. globulus is the most common commercially sold eucalyptus species. Its unique chemical make-up consists of a large concentration of oxides, which makes it the better expectorant. It is also a better choice for non-enveloped, or 'naked' virus, which are sensitive to its terpenoid ketone content. E. globulus is said to have a stronger tropism for the upper airway.
... E. radiata contains less oxides than E. globulus for slightly less mucolytic properties. But it has a high concentration of a monoterpene alcohol called alpha-terpinol. This constituent makes it the better choice for enveloped viruses, which are most sensitive to monoterpene alcohols. E. radiata is said to have a stronger tropism for the lower airway.
... E. stagerianna and E. citriadora are the most anti-inflammatory and sedating of these eucalyptus oils due to their aldehyde concentration. They are mild enough for children.
... E. polybractae contains more or less equal proportions of a moderate amount of ketones & oxides. It is a balanced mucolytic and antiseptic.
... E. smithii is mostly an expectorant due to its moderate oxide content. It is also anti-infectious and slightly antiseptic. It has a balanced nature.
... E. dives is mucolytic like E. polybractae, due to its ketone content. But it contains more (50%), and therefore has a narrower therapeutic margin than these other eucalyptus oils. It is used with care with older children, the elderly, the infirmed, and those with epilepsy.