[Adverse reactions to natural remedies].

There are only a few systematic epidemiological studies concerning the frequency of adverse reactions (AR) to natural remedies. However, there are numerous case reports which sometimes also include some detailed pathophysiological investigations. In general, four different categories of side effects to natural remedies can be distinguished: 1--at normal use; 2--at excessive use; in this regard many publications exist, since natural products are generally assumed to be safe and, therefore, are frequently taken in overdose; 3--induced by falsified products, e.g. through addition of steroids to for example "natural" antiasthmatics; 4--induced through omission of an efficient and proven therapy because of unshakable believe in "nature". Since conclusive studies in this matter are methodologically cumbersome and very difficult to perform, two newer studies that address these problems in special situations (oncologic patients) are the more interesting.