Clinical validation of grass pollen exposure chamber in patients with allergic rhinitis triggered by timothy grass

The fluctuation in concentrations of airborne allergens frequently presents a challenge to assessing the efficacy of allergen immunotherapy (AIT) in 'field' studies. Allergen exposure chambers (AECs) are specialized medical installations developed to expose individuals to allergens at defined and consistent concentrations under a controlled environment. The aim of the study was to validate the provocation test with timothy grass pollen as well as to assess its safety in the AEC in patients with allergic rhinitis.

In the ALLEC® AEC, varying concentrations of timothy grass pollen were dispersed. Allergic symptoms were measured by total nasal symptom score (TNSS), acoustic rhinometry, peak nasal inspiratory flow (PNIF) and nasal discharge volume. Lung function, assessed through peak expiratory flow rate (PEFR) and forced expiratory volume in the first second (FEV₁), was used to evaluate safety.

The consistency of the test was proved by the stability of environmental conditions, including temperature, humidity and CO₂ levels, as well as constant concentrations of grass pollen at predetermined levels ranging from 1000 to 10,000 particles per cubic meter (p/m³). Allergic individuals developed symptoms at concentrations of 3000 p/m³ and above, across all measured endpoints. Lung function was not affected throughout all the challenges. The reproducibility of symptoms was confirmed throughout the tests. The concentration of 8000 p/m³ together with a challenge duration of 120 min was found to be optimal.

The study demonstrates that the ALLEC® grass pollen exposure chamber provides a reliable and safe method for inducing repeatable symptoms in patients with allergic rhinitis. This approach can be effectively applied for allergy diagnostics and clinical endpoint determination during AIT.