- Subcutaneous allergen immunotherapy is effective in treating allergic airway disease. Disadvantages include immediate local and systemic adverse reactions and poor compliance. To obtain real-life efficacy and safety data through a prospective observational study of SIT in the allergist's office. We prospectively collected data from all patients with a diagnosis of allergic rhinitis and/or asthma and a specific immunoglobulin E-mediated sensitization to one or more aeroallergens who began SIT during the 2 year period 1 January 2005 to 31 December 2006. As part of the routine immunotherapy care patients were asked to complete a disease activity questionnaire before and yearly during the treatment. The primary outcome measure was the combined rhinitis and asthma symptoms scores. Data from patients completing at least 1 year of immunotherapy were analyzed. Altogether, 133 enrolled patients with a mean age of 22.7 years completed at least 1 year of SIT. The allergic rhinitis and asthma disease activity score decreased from a mean of 8.1 to 3.3 (rhinitis) and from 4.8 to 2.4 (asthma) on a 10 cm visual analogue scale after 1 year of SIT (P < 0.001 for all comparisons). Rhinitis medication use in all patients and asthma medication use in asthmatics decreased significantly. Mild local adverse reactions were almost universal. There were 11 patients (8%) who developed 14 immediate systemic, mild to moderate reactions. All reactions were successfully treated in the clinic; none required additional observation or hospitalization. In the hands of experienced allergists subcutaneous allergy immunotherapy is a safe and efficacious option for patients with allergic rhinitis and asthma.