Background and aims Allergic rhinitis annually reach epidemic proportions in Japan. Approximately 30 to 40% of the population suffers from allergic rhinitis during the spring season. Symptoms comprise rhinorrhea, nasal congestion, and sneezing accompanied by irritation and itching of the eyes. The Ohshiro Clinic started using the conventional Nd:YAG laser for the treatment of allergic rhinitis in 1993, and from 2005 we started using a diode laser-pumped Nd:YAG laser. From 2010, we adopted a novel 810 nm diode laser, and the present retrospective study examined the efficacy rate of the treatment of allergic rhinitis in the 2018 season with this system, compared with a previous study in 2011. We aimed to confirm the degree of improvement for each symptom to evaluate effectiveness of the diode laser treatment. Subjects and methods Between January 8, 2018 and April 30, 2018, a large number of patients consulted our clinic with the major complaint of seasonal allergic rhinitis. They underwent a blood test, and the antigen-specific serum IgE antibody titers were measured for a definitive diagnosis of cedar pollinosis. A total of 211 target patients were treated during the trial period. The average age of the target group was 36.3 years, 134 males, and 77 females. The target patients were treated with lower nasal turbinate mucosal irradiation using a diode laser (ADL-20, Asuka Medical) delivering 810 nm at 7.5 W, with a total energy per treatment of 240 J/cm2. We adopted a five-step evaluation in accordance with the Japanese Guidelines for Allergic Rhinitis 2014 for the symptoms of rhinorrhea, sneezing and nasal obstruction. We assessed the degree of improvement in the severity of these symptoms following diode laser treatment from baseline to one month after treatment, in addition to assessing patient satisfaction with the degree of improvement in their quality of life (QOL). Results The 211 patients positive for cedar pollinosis by the antigen-specific serum IgE antibody tests were broken down by month by number and by improvement, no change or exacerbation as follows. January, 18 patients: 33.4%, 44.4% and 22.2%, respectively. February, 29: 10.4%, 44.4% and 22.2%, respectively. March, 146: 60.3%, 31.5% and 8.2%, respectively. April, 18: 77.8%, 16.7% and 5.5%, respectively. The monthly respective improvement, no change or worse patient QOL as percentages were as follows: January: 16.7%, 44.4% and 38.9%. February: 17.3%, 13.8% and 68.9%. March: 61.6%, 29.5% and 8.9%. April: 94.4%, 0.0% and 5.6%. The values for prevention of exacerbation versus exacerbation for each month were: January, 77.8% vs 22.2%; February, 41.4% vs 58.6%; March, 91.8% vs 8.2%; and April, 94.4% vs 5.6%. The mean efficacy rate for the trial period in the present study was therefore 52.6% which compared very favorably with the mean efficacy rate in the 2011 study of 53.4%. Conclusions The results showed that the 810 nm diode laser offered a safe and effective solution for the uncomfortable symptoms of allergic rhinitis and could be well applied during the season of Japanese cedar pollen dispersion. Furthermore, a tendency towards high efficacy was demonstrated for laser treatment in class 6 cedar pollinosis patients, based on the specific IgE antibody test.