Eucalyptus  The healing powers of eucalyptus have been, and continue to be, widely known as a treatment for respiratory difficulties.  In fact, many cough medications available in your drugstore contain eucalyptus, as do various topical preparations for treating pain.  The whole breathing process is actually aided by eucalyptus, because it both helps to regenerate lung tissue as well as acting as an expectorant and decongestant.  

Reference: "ASTHMA and ALLERGIES", Dell Publishing, New York, NY, 1995, pages 220-221.