The 2010 WAO Grading System is a useful tool for accessing SR severity. SR to SCIT with airborne allergens are rare and all of our reacCons were grade 1 or 2. None of the commonly implicated risk factors was idenCfied in our paCents. A large scale study is needed to perform comparaCve analysis and to clarify the best surveillance and treatment of SR to SCIT. A first characterizaCon according to WAO's grading system Santos, Natacha ; Pereira, Ana Margarida; Silva, Rui; Torres da Costa, José; Plácido, José Luís Serviço de Imunoalergologia, Centro Hospitalar São João, E.P.E., Porto, Portugal Systemic reacCons (SR) to subcutaneous immunotherapy (SCIT) are unusual but potenCally severe. Poorly controlled asthma, large local reacCons, administraCon during pollen season and dose error are the more implicated risk factors, but studies have been hampered due to the variety of previously exisCng classificaCons. The aim of our study is to characterize SR to SCIT with airborne allergens occurring in our clinic from January 2008 to June 2010 and to classify them according to the WAO Subcutaneous Immunotherapy Systemic ReacCon Grading System 1 . 1 L. Cox, D. LarenasLinnemann, R. F. Lockey, G. Passalacqua; Speaking the same language: The World Allergy OrganizaCon Subcutaneous Immunotherapy Systemic ReacCon Grading System; J Allergy Clin Immunol 2010;125:56974. 2 J. E. AlvarezCuesta, J. Bousquet, G. W. Canonica, S. R. Durham, H. J. Malling, E. Valovirta. Standards for pracCcal allergenspecific immunotherapy. Ann Allergy Asthma Immunol. Allergy 2006: 61 (Suppl. 82): 1–20 CrosssecConal study with data collected from a paCent's immunotherapy record form. PaCent selecCon and SCIT administraCon followed EAACI recommendaCons 2 . During the study period, 19398 SCIT to airborne allergens were administered, and immediate reacCons (beginning < 30min), as well as late reacCons, were recorded. SR occurred in 13 paCents, ♂8:5♀, median age of 25 years old (689), in a total of 20 SR (0,1% of all administraCons). Allergic disease Immunotherapy Systemic reac6ons Composi6on Formula6on Administra6on Phase Time Manifesta6on WAO RhiniCs Grass Polymerized Rush InducCon Immediate Rhinorrhea 1z RhiniCs Mites Depot Classical InducCon Immediate Rhinorrhea 1z RhiniCs Mites Depot Classical InducCon Immediate Rhinorrhea 1z RhiniCs + Asthma Mites Polymerized Classical InducCon InducCon Late Immediate Rhinorrhea ConjunCval pruritus 1z 1z RhiniCs Mites Depot Classical InducCon InducCon InducCon Late Immediate Late Rhinorrhea Rhinorrhea Rhinorrhea 1z 1z 1z RhiniCs Mites Polymerized Classical InducCon Late Oropharingeal pruritus 1z RhiniCs Mites Polymerized Classical Maintenance Maintenance Immediate Late Rhinorrhea Rhinorrhea 1z 1z RhiniCs + Asthma Grass Polymerized Rush Maintenance Late Sneezing 1z RhiniCs + Asthma Mites Polymerized Rush InducCon InducCon InducCon Late Late Late Asthma Asthma Asthma 2z 2z 2z RhiniCs + Asthma Mites Polymerized Classical InducCon Late Asthma 2z RhiniCs + Asthma Mites Polymerized Rush InducCon InducCon Late Late Rhinorrhea > Asthma Nasal congesCon 2z 1z RhiniCs Grass Polymerized Rush InducCon Late Generalized erythema > Wheezing 2z RhiniCs Mites Polymerized Rush Maintenance Late Generalized erythema > Rhinorrhea > Shortness of breath 2d There were 14 (70%) late reacCons, with 5 of them occurring aner 3 hours (maximum 48 hours aner). Only 2 paCents had previous local reacCons, both with wheals < 5cm. All 3 paCents with SCIT to grass had the SR out of the pollen season. Table 1. CharacterizaCon of paCents and systemic reacCons