Positive patch test reactions to 2% cinnamic aldehyde were obtained from 2.8% of 34 males and 9.1% of 55 females. The 9.1% female reactivity may be traceable to perfumed cosmetics. Simultaneous Jasmin allergy is documented as is the occurrence of alpha-amyl cinnamic aldehyde in synthetic Jasmin. The relevance of these reactions is discussed. In two of the patients a proper diagnosis was not made from the original contact history. Only after a screening tray demonstration of cinnamic aldehyde allergy could a relevant history be taken from these patients.