To investigate the relationship between cytokine production in the nasal passages and late-phase allergic responses in patients exposed to birch pollen allergens.

A double-blind, randomized, placebo-controlled study was carried out involving birch pollen-allergic individuals. Overall, 20 participants exposed to birch pollen extract and 10 to a placebo over three consecutive days were included. The secretions from the nose were gathered at different time points within 24 hours on days 1 and 3 to evaluate 33 inflammatory mediators. The subjective symptom scores and objective measurements of nasal airflow were used to assess the clinical responses.

As compared to the placebo group, the participants exposed to birch pollen exhibited notably stronger clinical responses and demonstrated rapid increases in tryptase and soluble interleukin (IL)-33 receptor serum stimulation 2 (sST2) levels in nasal secretions shortly after allergen exposure. Eight participants out of 20 displayed elevated levels of IL-13 between 2 to 8 hours following allergen exposure.

This group also exhibited substantial changes in clinical parameters (subsequent waning in peak nasal inspiratory flow and increased nasal obstruction symptoms). These changes varied from those in people who did not display an IL-13 response, especially after 6 hours of exposure.

The occurrence of an IL-13 response is linked with both clinical symptoms and type 2 cytokine responses during the late phase following after being exposed to the allergen.