Sensitivity to Parietaria pollen in the Southampton area as determined by skin-prick and RAST tests

The pollen of Parietaria species is a well-recognized and important inhalant allergen in the Mediterranean area. Parietaria judaica (Pellitory-of-the-Wall) is native to the U.K., flowering from June to September, but is not usually considered to be of any clinical importance by U.K. allergists. We skin tested 62 patients with a clinical history of summer seasonal respiratory symptoms and a control group of 11 patients with perennial respiratory symptoms only. Each was skin tested in duplicate with extracts of grass pollen, birch pollen, Parietaria pollen, Dermatophagoides pteronyssinus, Cladosporium, Alternaria, nettle pollen and negative and positive controls, and serum samples were collected for RAST assays for Parietaria and nettle. Eight of the 62 patients in the main group showed skin reactivity to Parietaria. Five of these eight had never visited the Mediterranean area and therefore it is possible that sensitization occurred in the U.K. Thirteen of the 62 patients were skin reactive to nettle but there was no correlation between skin reactivity to Parietaria and nettle. This supports a recent report that, despite their close botanical relationship, no antigenic cross-reactivity exists between the two species. No correlation was seen between skin reactivity and serum RAST activity to Parietaria or nettle. It is not known whether exposure to Parietaria pollen contributes to the seasonal symptoms of the patients found to be skin reactive. None of the 11 patients in the control group was skin reactive to Parietaria.