Hyssopus Officinalis (hyssop)~ (Whole Plant, Leaves, Flowers, Oil) Internally: (flowering plant) bronchitis, upper repertory tract infections, and congestion, feverish illnesses and coughs in children, flatulence, and colic. Externally: (flowering plant) cuts and bruises. (oil) bronchial infections. (bath oil) nervous exhaustion. *Excessive use of essential oil may cause epileptic fits and death.