Sensitisation Profile of Patients with Positive Skin Prick Test to Amaranthaceae Pollen in the South of Portugal

Exposure to airborne pollen allergens is a major trigger of respiratory allergy, whose prevalence continues to rise throughout Europe. In southern Portugal, the Mediterranean climate and extensive vegetation diversity promote high pollen loads, particularly from the Amaranthaceae family. This retrospective observational study aimed to characterise the sensitisation profiles of patients with positive skin prick tests (SPTs) to Chenopodium album and/or Salsola kali, the dominant Amaranthaceae species in the region. Data from 346 patients were analysed, including demographic and clinical characteristics, SPT results, and specific IgE sensitisation to molecular allergens. Of these, 35% were positive for C. album only, 13% for S. kali only, and 51% for both. In molecular testing, 54% of S. kali-sensitised patients were positive to Sal k 1, whereas only 4% of C. album-sensitised patients were positive to Che a 1. Sensitisation to panallergens such as profilins and Ole e 1-like proteins was frequent, suggesting extensive IgE cross-reactivity between these taxa. A significant correlation in wheal size (r = 0.53, p < 0.0001) further supports shared allergenic determinants. Despite higher SPT positivity to C. album, S. kali is likely the predominant sensitising source in this population. These findings highlight the importance of molecular-based diagnostics to distinguish genuine sensitisation from cross-reactivity in Mediterranean settings.