Characterisation of systemic reactions to subcutaneous immunotherapy with airborne allergens and classification according to WAO 2010

BackgroundSystemic reactions (SR) to subcutaneous immunotherapy (SCIT) are rare but potentially severe. The use of different definitions and classifications hampered comparability between studies.AimsTo determine the frequency of SR to SCIT with airborne allergens, and to characterise and classify them according to the WAO 2010 recommendations.MethodsCross-sectional, retrospective study. Data on patients, immunotherapy and SR to SCIT were collected from the SCIT record forms. During the study period, 22,332 SCIT injections were administered (3732 patients).ResultsA total of 26 SR (0.1% of administrations) were recorded in 16 (0.6%) patients (median age 22 years, nine males, all with rhinitis and nine with asthma). Twenty-one (81%) SR occurred during the induction phase; eight (31%) in the first hour after administration. According to the WAO 2010 classification, 12 (46%) were grade 1 and 14 (54%) were grade 2. Most grade 2 reactions occurred in asthmatics, presented as mild asthma symptoms and resolved without need for medical observation. Only two individuals without asthma presented grade 2 reactions, both with concurrent cutaneous and low respiratory symptoms; both required medical observation and treatment despite late onset; 82% (n = 12) of grade 2 reactions were late. No grade 3–5 reactions were registered and only one patient needed adrenaline treatment. No risk factors for SR to SCIT were identified in this study.ConclusionsSCIT is a safe treatment when administered by trained staff. The WAO 2010 classification might be useful for retrospectively classifying the severity of reactions, although its usefulness in treatment decision needs further research.