Safety and Utility of Rush Immunotherapy with Aqueous Allergen Extracts for Treatment of Respiratory Allergies

BACKGROUND: Generally, allergen immunotherapy must be administered for three to five years. Meanwhile, rush immunotherapy (RIT) shortens the required duration for the build-up phase, thereby improving the therapy's convenience compared with conventional immunotherapy (CIT). However, RIT is often performed with modified allergens. Therefore, this study aimed to investigate the safety and utility of RIT with aqueous allergens. METHODS: Medical records of 98 patients sensitized with at least one inhalant allergen who had received subcutaneous immunotherapy for allergic rhinitis with or without asthma were retrospectively reviewed. All patients were classified into three groups: depot-RIT (n = 25), receiving RIT with depot allergen; aqueous-RIT (n = 48), receiving RIT with aqueous allergen; and aqueous-CIT (n = 25), receiving CIT with aqueous allergen. Patients who had received immunotherapy targeting only house dust mites were excluded. RESULTS: The proportions of patients presenting with a systemic reaction to depot-RIT, aqueous-RIT, or aqueous-CIT were 80.0%, 85.4%, and 48.0%, respectively (P = 0.002). The proportions of patients experiencing severe systemic reaction were 4.0%, 16.7%, and 8.0% in depot-RIT, aqueous-RIT and aqueous-CIT, respectively (P = 0.223). The proportions of depot-RIT and aqueous-RIT patients presenting with systemic reaction or severe systemic reaction did not differ significantly (P = 0.553 and P = 0.118, respectively). Significantly fewer depot-RIT (1.0 ± 0.2) and aqueous-RIT patients (2.0 ± 1.3) required outpatient clinical visits during the build-up phase, compared to those administered aqueous-CIT (13.6 ± 1.9; P < 0.001). Moreover, the build-up phase decreased to 17.4 ± 1.8 days in depot-RIT and 23.7 ± 10.9 days in aqueous-RIT, compared to 92.0 ± 12.5 days in aqueous-CIT (P < 0.001). CONCLUSION: RIT with aqueous allergen reduced the build-up phase duration and frequency of hospital visits, with acceptable safety levels. RIT with aqueous allergen may, therefore, be suitable for broad application to patients with respiratory allergies.