Namely
The Eucalyptus leaf has been used for hundreds of years in various remedies. For example, the plant is used in medicines to relieve the airways. In cosmetics, it is used for its flavor and antiseptic functions. It has recently been shown (Bachir, Selvakumar, 2012) that this oil may have an action in the anti-dandruff treatment of certain dandruff like Malassezia furfur. It is also effective against lice (pediculus humanus) by destroying the slow ones.
It would take a whole treatise, to treat all the known benefits of this plant, however, the essential oil that contains it in pure form can be problematic, containing for example terpenes (volatile VOCs). Cineole, which is included, can also cause neuronal toxicity and convulsions at high doses.