Birch pollen allergy: Evaluating symptoms in controlled and natural settings

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Created On: 29/11/2023

A study sought to investigate allergic rhinitis triggered by birch pollen across three distinct scenarios (nasal allergen challenge [NAC], environmental exposure chamber [EEC], and pollen season).

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Key take away

The environmental exposure chamber results were similar to nasal allergen challenge and natural exposure, indicating the environmental exposure chamber's usefulness in research.

Background

A study sought to investigate allergic rhinitis triggered by birch pollen across three distinct scenarios (nasal allergen challenge [NAC], environmental exposure chamber [EEC], and pollen season).

Method

The study enrolled 30 participants who exhibited allergic reactions to birch pollen, as confirmed by birch skin prick tests, specific immunoglobulin E (IgE) levels, and positive NAC results. These participants underwent two placebo exposures followed by two consecutive 4-hour exposures to airborne birch pollen, repeated on two separate occasions to assess the priming effect and reproducibility.

The nasal response was determined by a total corrected nasal symptom score (ΔTNSS) of ≥ 5 during EEC and NAC. The major outcome was the measurement of TNSS during the last 2 hours of the initial allergen exposure. Evaluation of TNSS was also done during natural exposure.

Result

The most common dose that led to a positive ΔTNSS during the NAC was 175.2 ng/200 μL. Overall, 18 individuals had a ΔTNSS of ≥5 during the last 2 hours of the initial exposure, while 21 participants showed positive responses in all four exposures. The mean ΔTNSS was 1 with the placebo and increased to 6 with birch exposure.

The exposures were consistent and did not show any signs of a priming effect. The concentration of airborne Bet v 1 was 25 ng/m3, and pollen levels measured 279/m3 during the pollen season. Notably, 67.9% of participants experienced a TNSS of 5 or higher during the peak pollen season.

Conclusion

The outcomes from the EEC closely paralleled those achieved through NAC and natural exposure, underscoring the value of EEC in investigations of allergic rhinitis. The study successfully met its primary goal, with 60% of participants exhibiting nasal responses.