Eucalyptus oil is thought to function in a fashion similar to that of menthol by acting on receptors in the nasal musoca, thereby facilitating healthy breathing.
The major constituent in eucalyptus leaves is a volatile oil known as eucalyptol (1,8-cineol). In order to provide its potent effects, the leaf oil should contain approximately 70-85% eucalyptol.
In the world of the Aromatherapy, the "clean" feel of eucalyptus is associated with the respiratory system, sinuses, flu, and allergies. Very popular with the sauna crowd. In test studies, eucalyptus species, have been shown to possess antibacterial actions against such organisms as bacillus subtilis, as well as several strains of streptococcus.*