Three‐Year Longitudinal Evaluation of Timing Effects on Subcutaneous Immunotherapy Efficacy and Safety in Allergic Rhinitis

Allergic rhinitis (AR) is a chronic inflammatory condition of the nasal mucosa characterised by a distinct diurnal pattern of symptom exacerbation, with peak nasal congestion typically occurring during the night and early morning hours [1]. This temporal variation in symptom severity is thought to be mediated, at least in part, by circadian rhythms, which not only regulate immune system activity but also influence the pharmacokinetics and pharmacodynamics of various medications, potentially affecting their therapeutic efficacy and safety [2, 3]. Chronotherapy, the strategic timing of medication administration to align with biological rhythms, has emerged as a promising approach to optimise treatment outcomes. In the context of allergen immunotherapy (AIT), previous research has demonstrated temporal variations in treatment efficacy. For instance, sublingual immunotherapy (SLIT) demonstrated greater efficacy when administered in the morning compared with evening in an ovalbumin-induced AR model [4]. Conversely, evening administration of SLIT for 1 year resulted in better asthma control than morning in children with allergic asthma [5]. Despite these insights, the impact of dosing time on the efficacy and safety of subcutaneous immunotherapy (SCIT) in AR patients remains unexplored. In this longitudinal study, we investigated the temporal effects of SCIT administration by comparing morning dosing (MD, 8 AM–12 PM) with afternoon dosing (AD, 2 PM–6 PM) in 65 house dust mite (HDM)-sensitive AR patients receiving Alutard SQ, with 27 in the MD group and 38 in the AD group. Patients were followed for 3 years, with comprehensive questionnaire surveys and blood specimens collected at baseline, 6, 12, 24 and 36 months. Statistical analyses were performed using R 4.4.1. Linear mixed-effects models were employed to assess the effects of treatment duration, dosing time and their interaction on symptom scores and immunological markers, with random effects accounting for within-subject variability. Adverse events were compared between groups using Mann–Whitney tests. Data are presented as means ± SEM, with statistical significance set at p < 0.05. Our findings revealed significant improvements in nasal and ocular symptoms, including sneezing, nasal congestion, itchy nose and runny nose, at all follow-up timepoints in both groups (p < 0.05, Figure 1A). To maintain clarity, statistical differences between each timepoint and baseline were omitted in Figure 1A, highlighting significant trends and differences between groups over time as key findings. Notably, the AD group demonstrated significantly greater improvement in runny nose at the 6-month follow-up (p < 0.05) and showed a trend towards better improvement in nasal congestion and overall visual analogue scale (VAS) scores compared with the MD group (p < 0.1). These results suggest that afternoon SCIT administration may facilitate earlier symptom relief, potentially enhancing early treatment satisfaction and adherence—critical factors in AIT success. Safety analysis over the 3-year treatment period revealed that the most common adverse events were mild local reactions (0.68%), severe local reactions (0.03%) and mild systemic reactions (0.46%). No moderate or severe systemic reactions were observed in either group. The AD group exhibited a higher frequency of overall adverse events compared with the MD group, but no statistical significance (Figure 1B, p = 0.07 and p = 0.11). However, the frequency and percentage of systemic adverse events were significantly higher in the AD group (Figure 1B, both p < 0.05), with no significant difference in local reactions between groups. Among 45 patients (20 MD, 25 AD), the AD group exhibited enhanced immune responses. The reduced cohort in Figure 1C represents participants who completed questionnaires but declined blood sampling. Analysis of the Figure 1C subset and the figure with baseline data are available at https://doi.org/10.17605/OSF.IO/3A689. Immunological markers increased more significantly in the AD group, with higher specific immunoglobulin E (sIgE) levels for Der p 1, Der p 2 and Der p, higher Der p 1 sIgE/total IgE ratios at 24 and 36 months, higher Der p 2 sIgE/total IgE ratios at 36 months, higher Der p 2 sIgG4 levels at 12 months, higher Der p sIgG4 levels at 24 months, higher Der p 1 sIgG1 and Der p 2 sIgG1 at 6 and 12 months, and higher Der p IgE blocking factor (BF) (Figure 1C), respectively. IgE BF was measured as reported [6]. These immunological findings suggest that afternoon SCIT administration may accelerate early immune modulation, enhance protective mechanisms and promote faster clinical improvements. The earlier enhancement of IgG4 responses in the AD group, which plays a crucial role in blocking allergen–IgE interactions [7, 8], aligns with the observed earlier relief of rhinorrhoea. Similarly, the more pronounced IgG1 response, which mediates early allergen neutralisation [9], may contribute to the accelerated clinical improvements observed in the AD group. In conclusion, our study provides evidence that afternoon SCIT administration may accelerate symptom relief (particularly at the 6-month timepoint) and enhance immunological responses compared with morning dosing, albeit with a slightly higher incidence of mild systemic adverse reactions. These findings suggest that chronotherapeutic optimisation of SCIT administration timing could offer clinical benefits, particularly for patients with refractory rhinorrhoea or those prioritising early symptom relief. However, the marginally increased risk of systemic reactions warrants careful consideration. We propose that afternoon administration (within a 2–6 PM window) could be considered as an adjunct optimisation strategy, particularly in patients who may benefit from earlier symptom control. Future multi-centre studies with larger cohorts and rigorous control of confounding factors are needed to validate these findings and further elucidate the mechanisms underlying temporal variations in SCIT efficacy and safety. H.L. formulated and designed the study, analysed the data, produced most of the figures and tables, and drafted part of the manuscript. X.Y. and Y.W. analysed part of the data and drafted part of the manuscript. D.C., X.C., M.P., C.C., H.C., X.L. and W.L. reviewed and edited the manuscript. Wb.L., Wp.W. and R.X. obtained funding, designed the study, provided supervision, and reviewed and edited the manuscript. We extend our gratitude to all the participants in this study. Special thanks to Mr. Zhibin Lin and Ms. Meirong Huang for their invaluable assistance with the follow-up work. This study was approved by the Ethics Committee of the First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Approval No. 2018194). Sixty-five house dust mite (HDM)-sensitive AR patients receiving SCIT with Alutard SQ were enrolled. All the participants signed the informed consent form. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request. The analysis of the Figure 1C subset and the figure with baseline data can be available through https://doi.org/10.17605/OSF.IO/3A689.