Published studies indicate that Subcutaneous Immunotherapy (SCIT) is an effective treatment of allergic airway diseases, under the conditions of a careful selection of patients and the use of quality allergen extracts for treatment vaccines. Risk/benefit assessments of both the allergic disease and treatment options are important for evaluating the indication for SCIT. Allergic rhinitis, the most common allergic disease, affects about 20% of the adult population. Allergic asthma varies in prevalence in different countries, but in the Western world, it usually affects more than 5% of the population. For patients with a constant need for preventive pharmacotherapy, early initiation of allergen immunotherapy is advantageous, while the severity of the disease is modest and when the possibility of prevention of asthma is the greatest. Asthma is potentially more severe than rhinitis in relation to acute attacks, hospital admissions, and possibly in days of missed work or school. Furthermore, asthma may develop into chronic, irreversible pulmonary impairment.