D1.201 - Safety and Effectiveness of Subcutaneous Immunotherapy with Non-Homologous Aeroallergen Mixtures: A Real-World Study

Subcutaneous immunotherapy (SCIT) is the only treatment capable of modifying the natural course of allergic rhinoconjunctivitis (ARC). Although guidelines recommend homologous allergen extracts, non-homologous mixtures are frequently used in polysensitized patients. Aim:To evaluate the safety and effectiveness of SCIT with a mixture of aeroallergens (Poliplus Roxall®).

We conducted a cross-sectional observational study including patients with ARC who initiated SCIT with a non-homologous aeroallergen mixture (Poliplus Roxall®) at the Allergy and Immunology Department between 2022 and 2024 (treatment duration ≥1 year). Data were extracted from medical and nursing clinical records and included sociodemographic characteristics, extract composition, patient- and physician-perceived clinical improvement, occurrence of adverse reactions (local or systemic; immediate or delayed), and concomitant medication use before and after the initiation of immunotherapy.

Twenty-five patients were included (56% female), with a median age of 20 years (range: 9–51; IQR: 15). All had ARC; 32% (n=8) had asthma and 16% (n=4) atopic dermatitis. All patients underwent an ultra-rush induction protocol. Allergen mixtures included mites with grass pollens (n=20), grass pollens with tree pollens (n=3), grass pollens with weed pollens (n=1), and mites with cat epithelium (n=1). A total of 12 local ARs (48%) were recorded: 25% (n=3) immediate and 75% (n=9) delayed, characterized by erythema, edema (<10 cm), and granulomas. No systemic ARs were observed. Atopic dermatitis was the only factor associated with AR occurrence (p=0.03; OR 14.3). Perceived improvement was reported by 76% (n=19). A significant reduction in medication score was observed after SCIT (p<0.003; median 1 [range 1–3; IQR 1] vs. 1 [range 0–2; IQR 1]). No significant differences were found in GINA step before and after SCIT. Female sex was associated with absence of perceived improvement (p=0.02), although not with absence of objective improvement in medication score. Four patients (16%) discontinued or suspended treatment, two due to financial constraints and two due to lack of perceived improvement.

SCIT with non-homologous aeroallergen mixtures demonstrated a favorable safety profile and clinical effectiveness in ARC. Atopic dermatitis emerged as a risk factor for ARs. These findings support the safe use of SCIT in real-world clinical practice and highlight the relevance of atopic comorbidities in risk stratification.