The aim of this study was to assess the safety and efficacy of injection AIT for HDM allergens in elderly patients with allergic rhinitis and a confirmed HDM allergy. The study with double blind, placebo controlled trial was conducted in one centre. A total of 92 patients ranging from 65 to 73 years of age were recruited from the outpatient allergy clinic to assess their eligibility for inclusion in the study. First, there was a need for pre screening approximately 157 patients with inhalant allergies and the right age. Additionally, the patients included in the study all had a positive skin prick test (SPT), were positive for specific immunoglobulin E (sIgE), and had positive nasal provocation tests (NPTs) with D.pteronyssinus and D. farinae allergens. Patients with a clinical allergy and/or a positive skin prick test and specific IgE to other inhalant allergens (including other pollens) were excluded from the study. A careful examination of the eyes, ears, nose, and throat was performed on all patients. The severity of perennial allergic rhinitis (AR) was assessed using the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines. The patients were randomly selected to receive PURETHAL Mites (20,000 AUeq/ml, HAL Allergy BV, Leiden, The Netherlands, containing major allergen equivalents of 14.0 μg/ml group 1, and 20.0 μg/ml group 2, measured by ELISA in the extract prior to modification and adsorption on aluminium hydroxide) or a placebo (Figure 1). The recruitment period was limited to three months (April-June). Purethal Mites were administered as perennial therapy using the following regimen: 1 dose- 0.1 ml, 2 doses - 0.2 ml, 3 doses - 0.5 ml every week, and 0.5 ml every four weeks during 24 months.