herbs that promote dilation of the blood vessels causing a reduction of blood pressure
Agents that act as blood vessel dilators (vasodilators) and open vessels by relaxing their muscular walls. For example, nitroglycerin is a vasodilator. So are the ace (angiotensin-converting enzyme) inhibitors. ... (12 Dec 1998) ... 
Vasodilators: Agents that act as blood vessel dilators (vasodilators) and open vessels by relaxing their muscular walls. For example, nitroglycerin is a vasodilator. So are the ACE (angiotensin converting enzyme) inhibitors.
Any medicine that dilates (widens) the arteries.