"Sometimes flu or colds come with raw, irritated respiratory linings."...."Expectorants help loosen respiratory secretions so they can be coughed up. Helpful expectorants include.... eucalyptus (Eucalyptus globulus), ...."

"Most essential oils have some antibiotic effects. The best way to use them is in a steam inhalation, which takes their healing components deep into the lungs. Eucalyptus oil is especially helpful for pneumonia, because it not only is a decongestant but also helps you cough up mucus."

Reference: Linda B. White, M.D, and Steven Foster, in the book entitled "The Herbal Drugstore, The Best Natural Alternatives to Over-the-Counter and Prescription Medicines!", Interweave Press, USA, 2000, first excerpt above is from page 180, and the second excerpt above is from page 461