The authors report a study of patch test sensitivity to the allergen of Primula obconica (2-methoxy-6-n-pentyl-p-benzoquinone), which has recently been isolated and synthesized. The amount of primin necessary to give a positive reaction to a closed patch test in all patients sensitive to Primula obconica is 1 μg or less. The reactions to open patch tests were stronger than those obtained with closed patch tests. Since the amount of allergen in the plant varies considerably, pure primin should be used to avoid strong patch test reactions and false negative tests. It is suggested that the substance studied may prove useful for experimental work, especially in the United States where preexisting sensitivity to Primula obconica is considered to be rare.
Fregert S, Hjorth N, Schulz K. Patch Testing With Synthetic Primin in Persons Sensitive to Primula obconica. Arch Dermatol. 1968;98(2):144-147. doi:10.1001/archderm.1968.01610140042009