Double-blind placebo-controlled peroral challenges in patients with delayed-type allergy to balsam of Peru

Patch tests (PTs) with spices, such as clove, cinnamon, Jamaica pepper and vanillin sugar, and with balsam of Peru were made on 29 patients 0.8-2.9 years after an allergy to balsam of Peru had been detected. Positive reactions to balsam of Peru were seen in 17 patients, and to clove, Jamaica pepper or cinnamon in 5. Double-blind placebo-controlled peroral challenges (DBPCPCs) with balsam of Peru and spices (active substances) were performed on 22 patients. A substantial increase (30-280%) in the number of palmar vesicles after the DBPCPC with the active substances, but not with placebo, was seen in 8 patients, an increase with both the active substances and placebo in 3, and with placebo but not the active substances in 1 patient. 4 of the 8 patients with positive DBPCPCs with the active substances were negative to balsam of Peru in the 2nd PT. No other objective symptoms were seen after the DBPCPCs. Balsam of Peru and the spices were retested 3 months after the DBPCPC. Both alleviation and aggravation of the PT reactions were seen. It is concluded that ingested flavoured foods might cause systemic contact reactions in some patients with allergy to balsam of Peru, but the benefits of a flavour-avoiding diet are questionable in all of them.