Description Eucalyptol is a natural organic compound which is a colorless liquid. It is a cyclic ether and a monoterpenoid. Eucalyptol is an ingredient in many brands of mouthwash and cough suppressant. It controls airway mucus hypersecretion and asthma via anti-inflammatory cytokine inhibition. Eucalyptol is an effective treatment for nonpurulent rhinosinusitis. Eucalyptol reduces inflammation and pain when applied topically. It kills leukaemia cells in vitro.