Pelargonium (Pelargonium sidoides DC and P. reniforme Curtis) is reported to have immune modulating properties and antibacterial activity, and Pelargonium extracts have been used for the treatment of respiratory tract and gastrointestinal infections. Introduced in the early 1980s in Germany, Umckaloabo® (ISO Arzneimittel), an ethanolic extract of the roots of P. sidoides and P. reniforme, was the first Pelargonium- derived product to be commonly used in a country in the EU. According to the Umckaloabo® product information, this extract has no known adverse effects. However, there is a theoretical risk of interactions with anticoagulants such as warfarin, and antiplatelet drugs, such as aspirin (acetylsalicylic acid). To date, the Uppsala Monitoring Centre has, through the WHO international pharmacovigilance programme, received 34 case reports of allergic reactions suspected to be associated with the use of Pelargonium extract, all originating from Germany. In a number of these reports, the description and timing of the event was indicative of an acute Coombs and Gell Type I hypersensitivity reaction; two of these patients needed treatment for circulatory failure. So far, the experience of such reactions is limited to Germany. Since Pelargonium- containing herbal products have recently been approved in a number of other countries, the possibility of the occurrence of allergic reactions has become of more general interest and further information regarding these products is needed.