Quassia is anthelmintic: An enema with warm Quassia tea has been used for threadworms; Quassia is also used to kill pinworms and roundworms. Externally, it has been used in lotions for lice and similiar parasites.
Quassia's bitter principle improves Appetite and Digestion. Quassia is internally used for problems with Stomach, Intestines, Gallbladder and Liver. It is used to add bitterness to beer, liqueurs and soft drinks. Quassia has also been used for rheumatism and dyspepsia.

Caution: Internal use of larger amounts may irritate the stomach and cause nausea and vomiting!

Warning: Quassia is an anticoagulant, and should therefore not be taken together with other anticoagulants like Warfarin. Quassia is not recommended for pregnant women or for those who have stomach/duodenum ulcers.

As an insecticide, Quassia is commercially used against flies, aphids, woolly aphids and spider mites.