We have described ten cases of respiratory allergy to the pollen of Mercurialis annua in the area of Bordighera (Riviera dei Fiori) on the Italian Mediterranean coast. The incidence of sensitivity is only 0.9% in a population of 1081 patients with pollinosis. Since the Euphorbiaceae family (spurges) contains strongly sensitizing allergens (eg, seeds of Ricinus communis and latex of Hevea brasiliensis) our findings raise the possibility that respiratory allergy to the pollens of Mercurialis annua and other spurges has been underestimated throughout the world.