Cross-reactivity between Parietaria judaica and Parietaria officinalis.

The relative allergenicities of Parietaria judaica and Parietaria officinalis have been studied by in vivo and in vitro techniques and a strong resemblance has been shown, with common allergenic polypeptides, though they differ in a group of anodic proteins. In vivo activity was very similar and both pollen extracts reacted with sera from patients who were sensitive to P. judaica, thus demonstrating a high rate of cross-reactivity. Extracts from both species may therefore be used interchangeably in diagnosis and immunotherapy.