Propolis has been used since ancient times in folk medicine for its alleged beneficial effects. It is a potent sensitizer and is well recognized as a cause of occupational allergic eczematous contact dermatitis in apiarists. Recently, there has been an increase in allergic eczematous contact dermatitis because of nonoccupational exposure to propolis in "natural products" and biocosmetics. This report describes a patient who had acute oral mucositis with ulceration as a result of using propolis-containing lozenges.