Belladonna is a plant. The leaf and root are used to make medicine. belladonna is used as a sedative, to stop bronchial spasms in asthma and whooping cough, and as a cold and hay fever remedy. It is also used for Parkinson disease, colic, motion sickness, and as a painkiller. Belladonna is used in ointments that are applied to the skin for joint pain (rheumatism)