Warfarin interaction with Matricaria chamomilla.

No cases have been reported of Matricaria chamomilla potentiating the effects of warfarin. Nevertheless there is a theoretical risk for potentiation, since the herb is thought to be a coumarin constituent. We describe the case of a 70-year-old woman who, while being treated with warfarin, was admitted to hospital with multiple internal hemorrhages after having used chamomile products (tea and body lotion) to soothe upper respiratory tract symptoms. Patient education on the potential risk of taking chamomile products while being treated with warfarin is necessary to avoid such occurrences.