Horehound's bitterness stimulates the appetite and also promotes bile, making large doses laxative. The whole herb and its derivatives are used in thousands of lung medications around the world, especially for treating bronchitis and coughs. The essential oils and marrubiin dilate the arteries and help to ease lung congestion.

The herb apparently causes the secretion of a more fluid mucus, which is more readily cleared by coughing. Marrubiin also normalizes the heart beat and is a weak sedative. At one time, horehound was suggested for relieving menstrual pain and slowing a rapid heart beat. Since it also induces sweating, it has been used to reduce fevers, even those associated with malaria. It is less commonly used as a decoction for skin conditions. Old recipes call for the leaves to be boiled in lard and applied to wounds.