Uncovering the Distinct Role of Phleum p 4 in Grass Pollen Allergy: Sensitization Patterns in 1963 Swiss Patients

Grass pollen allergies significantly contribute to atopic diseases such as asthma and allergic rhinitis, resulting in considerable healthcare burdens. Objective: In this study, molecular sensitization patterns to grass pollen in Swiss patients were addressed. The research utilized a retrospective cohort approach using ImmunoCAP™ ISAC testing from October 2015 to July 2020. Clinical histories, demographics, and skin prick test results were collected for analysis. The minimum patient age was 18 years and the average patient age was 41.3 years, with a female predominance (68.5%). In total, 4814 measurements were analyzed. Allergic rhinitis was the most common clinical symptom, followed by asthma and urticaria. A total of 1963 patients (40.8%) revealed sensitization to grass pollen. The most common sensitizations were found to the major allergens Phl p 1 (86%) and Phl p 5 (65%), but also to Phl p 4 (62%). Monosensitization was mostly found to allergens Phl p 1 (266/13.5%) and Phl p 4 (157/7.9%), and less so to Phl p 5 (33/1.7%). Notably, the Phl p 4-monosensitized subgroup showed only an 18% positivity rate in skin prick tests and presented mostly with urticaria. This study gives insights into the spectrum of grass pollen allergies in a Central European setting and underscores the possibly underestimated role of Phl p 4 among grass pollen allergens, especially in a subgroup that suffers mainly from seasonal urticaria. Monovalent sensitization to Phl p 4 can also cause seasonal rhinitis and might therefore be missed if only Phl p 1/p 5 are tested. A better understanding of sensitization patterns will further improve diagnosis and treatment options.