Birch rust allergy as a novel autumnal trigger of seasonal airway symptoms

Accurate identification of allergenic triggers is essential for diagnosis, prevention, and management of airway allergies. In Tromsø (in northern Norway), birch rust (BR) spores are released in large quantities during autumn, a period with minimal dispersal of other environmental aeroallergens. This seasonal spike in BR spores coincides with an increase in symptoms of conjunctivitis, rhinitis, and asthma.

Our aim was to investigate whether exposure to BR spores is associated with allergic airway symptoms in autumn.

A total of 31 patients and 17 controls residing in Tromsø used a visual analog score to record their daily airway allergy symptoms from August 4 to October 14, 2020. Levels of specific IgE against BR and other relevant aeroallergens were measured in 13 patients and 7 controls. Skin prick testing for BR was conducted in 5 patients and 2 controls. Because of the lack of commercial reagents, test extracts from sampled BR spores were developed and produced during the study period. Airborne spore and pollen counts were collected from a monitoring station in Tromsø.

The mean symptom visual analog scale scores were significantly higher in the patients than in the controls. Of the 13 patients tested, 10 (76.9%) demonstrated specific IgE reactivity to BR spores. All 5 patients undergoing skin prick testing showed positive reactions to BR extracts.

These findings suggest that BR spores may represent previously unrecognized aeroallergens contributing to seasonal allergic airway symptoms in autumn. Further studies are needed to validate these preliminary observations and to clarify the underlying nature of this allergy.