The study will assess the effectiveness of AIT treatment in real clinical practice in Germany.

Allergic rhinitis (AR) affects 23-30% of the European population and is associated with a major burden on public health. AR and asthma frequently coexist, and may both be caused by allergen exposure. While the efficacy of AIT, i.e. reduce symptoms and medication use in patients with AR and asthma, has been demonstrated in several randomized clinical trials, little is known about the use and effectiveness of AIT in real world clinical practice.

This study is a retrospective database study that uses real-world data from Germany. The study population consists of AR patients with and without asthma treated with AIT and matched controls not treated with AIT. Information about the patients and treatments will be obtained from the 'BKK German Sickness Fund Database' from 2007 until 2017.

Inclusion Criteria for the AIT cohort:

• At least two index-AIT prescriptions during the first FU-year
• At least one confirmed AR diagnosis during the study period
• Continuous enrollment (no gaps in insurance time-defined by days) for 12 months before the index event (in the pre-index period)
• Continuous enrollment (no gaps in insurance time-defined by days) for at least 12 months after the index event (in the post-index period)

Inclusion Criteria for the Control Cohort:

- For the control groups, the same inclusion criteria will apply, with the exception of inclusion criterion 1, i.e. controls have not received AIT before baseline.

Exclusion Criteria:

- AIT prescription 12 months before the index event (in the pre-index period) for the AIT treatment group

Allergic rhinitis patients with and without asthma