For seasonal allergy sufferers, rain is usually thought of as a friend—it washes the pollen out of the air. However, there are circumstances in which a particular type of wet weather event can make things much worse: thunderstorms. Asthma epidemics have occurred under such circumstances and have affected patients who have never exhibited asthmatic symptoms before. The most recent severe episode occurred in Melbourne, Australia, in 2016, with 8500 emergency asthma visits and nine deaths.[1]
Recently in the Journal of Allergy and Clinical Immunology, Dr Gennaro D'Amato and colleagues[1] explored the nature of this phenomenon and implications for the future. The authors point out that although rare, these events are expected to occur more often with anticipated climate change. According to the authors, the evidence for this so far is limited to pollen and outdoor mold seasons—but even in the northeastern United States, that is about three quarters of the year.
How It Happens
Pollen grains are large (up to 35 µm in diameter)[2]and usually do not make their way down to the bronchial tree. During a thunderstorm, however, these grains are swept up by a dry updraft, ruptured by high humidity at the cloud base, then forced down by cold air.
