In Rome olibanum alone is employed; in other places benzoin, storax, lign, aloes, cascarilla bark, cinnamon, cloves and musk are all said to be occasionally used.
The aromatic bitters such as chamomile flowers, cascarilla bark, hops, orange peel and others contain in addition small quantities of essential oils which increase their local action.
The bitterness is imparted by such substances as bitter orange rind, gentian, rhubarb, quassia, cascarilla, angostura, quinine and cinchona.