OBJECTIVETo investigate the incidence of local reactions (LRs) and systemic reactions (SRs) of subcutaneous immunotherapy (SCIT) and to analyze the potential risk factors of such reactions in Chinese population.

METHODThis is a retrospective study on 234 dust mite sensitized patients with allergic rhinitis and asthma who received allergen immunotherapy in our hospital from 2003 to 2010. Chart review was conducted to capture clinical data of reactions to immunotherapy. Parameters included signs and symptoms, the onset of reaction, and interventions in treating such reactions, particularly, the administration of epinephrine (EPI) and adjustment of vaccine dosage due to LRs and SRs.

RESULTThe 234 patients received a total of 7679 injections. Among them, 4973 LRs (64.8%) and 235 SRs (3.1%) were observed in 67 patients (28.6% of all patients). SRs included respiratory symptoms (205 events, 88.4%) and cutaneous symptoms (31.5%). Of the total of 235 SR events, 212 (90.2%) were presented as mild SRs and 23 (9.8%) were in severe SR category (grade III and grade IV, EAACI grading system). Overall, severe SRs accounted for 0.3% of total injections. Seventeen of the 23 SR events required epinephrine treatment (0.2% of total injections). Of the 67 patients, 61 completed the course of treatment after dose adjustment; 36 patients had their doses decreased prior to further advancing to target dose. Nineteen subjects tolerated splitting two injections at 30 minutes interval. Six patients advanced the dose based on protocol and another 6 had to stop immunotherapy. Most of the SRs (77.4%) occurred during the maintenance phase of immunotherapy. The levels of TIgE, SIgE D1 and SIgE D2 were found to be significantly higher in patients with SRs comparing to patients without SRs (P < 0.05). SRs more commonly occurred in patients with age less than 14 years than their older counterparts (95.5% vs. 85.6%, OR = 3.58, 95%CI = 1.040 - 12.322, P < 0.01). The incidence of SRs were significantly higher in asthma patients who received SCIT than non-asthma patients (OR = 2, 95%CI = 1.136 - 4.624).

CONCLUSIONOur study suggests that risk factors of SRs include maintenance phase (higher allergen vaccine doses), patients with asthma, age of less than 14 years, higher levels of TIgE, and SIgE D1 and SIgE D2. Effective management includes proper dose adjustment, splitting doses into 2 injections at 30 min apart, and strictly following immunotherapy indications.