Validation of an Environmental Exposure Chamber for Assessment of Allergy to Grass Pollen

An environmental exposure chamber (EEC) is a health facility that enables allergic symptoms to be induced in a controlled manner in persons sensitized to a dispersed allergen. We performed a study at our institution to technically and clinically validate an EEC in patients allergic to grass pollen.

We developed a new EEC inside a clean room (ISO-8 class) measuring 15.6 m². During the technical validation, the patient's exposure conditions were simulated by ensuring homogeneous distribution of the allergen with a particle disperser and monitoring both particle and pollen grain concentrations. Temperature, pressure, and humidity were also registered. A total of 31 volunteers were exposed to Phleum pratense pollen in the EEC. Of these, 25 were allergic (cases), with symptoms of rhinoconjunctivitis with or without asthma, and 6 were not (controls). One control and 2 cases were exposed twice to check reproducibility, generating a total of 34 challenges. The test was stopped once the positivity criterion was reached or the patient completed 90 minutes in the EEC.

Both the stability of particle concentrations and approximation to the pollen sample concentration were guaranteed. All challenges with controls were negative. Among the cases, 15% of challenges were negative and 85% were positive. No severe or late reactions were observed. Volunteers exposed twice to the same pollen had the same result in both challenges.

Our EEC proved to be a specific, safe, and reproducible tool for the diagnosis of grass pollen allergy.