ObjectivesImmunotherapy is the gradual administration of increasing doses of allergens to reduce or eliminate the patient's adverse clinical response following exposure to these allergens. The goal of the current study was to evaluate the effectiveness of subcutaneous immunotherapy in patients with allergic diseases referred to the Bushehr Asthma and Allergy Clinic, Iran. Materials and methodsPatients with respiratory allergic diseases, who had positive skin prick test, randomly enrolled in this observational study and underwent immunotherapy for one year. To evaluate the efficacy of immunotherapy, two questionnaires were completed for all the patients before and one year after the start of immunotherapy, including the Total Nasal Symptom Score (TNSS) and Asthma Control Test (ACT). ResultsA total of 878 patients with asthma or allergic rhinitis disorder [53.6% (n=471) male and 46.4% (n=407) female] with a median (IQR) age of 28.0 (12.0–35.0) years were randomly enrolled in this observational study. Five hundred forty-nine patients (64.8%) were over 18 years old and 298 patients (33.9%) were under 18 years old, the age of the other patients was not known. The median (IQR) duration of disease was 84.0 (36.0–138.0) months. Rinithis allergy had most frequent than asthma [39.9% (n=350) vs. 22.2% (n=195), respectively] and 218 patients (24.8%) have both of them. After the treatment, 234 patients (54.5%) completely stop and 26.3% patient (n=113) used less than half of the drugs. The mean TNSS (n=259) and ACT (n=186) scores for patients had significant difference before and after immunotherapy [13.64 vs. 5.68, P<0.001; 7.91 vs. 17.43, P<0.001, respectively]. ConclusionThe mean TNSS and ACT score before and after the treatment significantly improved the patients’ symptoms. To conclude, standard immunotherapy can be effective in patients with moderate to severe allergic rhinitis and mild to moderate persistent allergic asthma to reduce clinical symptoms.