An interesting, if infrequent, phenomenon is that of thunderstorm-induced asthma. There have been reports all over the world, including the United States, Australia, the United Kingdom and Europe of asthma epidemics occurring during and shortly after thunderstorms.
Many of us are aware that weather/temperature changes and allergen exposure are among the most frequent triggers of asthma episodes. It is not uncommon to hear about people with asthma who have severe asthma flares after visiting a friend who has a cat, or after cleaning out an attic or garage. The spring and fall temperature swings are often associated with increases in doctor and hospital visits for asthma.
In November 2016, emergency departments in Melbourne, Australia were inundated with an influx of people suffering with severe asthma symptoms. This happened during the Australian spring pollen season following an evening of thunderstorms. 8500 people required medical attention and 9 people died from asthma during a 2 day period. Many of these people were previously diagnosed with asthma but many had allergic rhinitis/hay fever with no history of asthma.
We usually think of rainfall as cleansing the atmosphere of pollen. So how can thunderstorms trigger asthma symptoms, even in those without a history of asthma? There are several theories but the most widely held opinion is that during a thunderstorm, the warm updrafts carry pollen and mold particles toward the thunder clouds. Both electrical and osmotic forces from lightening and sudden changes in humidity cause rupture of pollen grains and mold particles, which are subsequently forced back toward land in thunderstorm downdrafts. The original pollen grains, rarely less than 10 microns in size are typically too large to be inhaled into the lung where they can trigger asthma. But after rupture of the pollen grains during a thunderstorm, the resulting fragments are much smaller, 0.5-2.5 microns in size, and can easily be inhaled into the lower airway. This can trigger asthma in those people with allergy, even in those who do not have asthma.
Once again, if you have allergies or asthma, the best advice is to listen to what your mother told you and stay indoors during a thunderstorm!
Alan Aarons, M.D.
Allergy Partners of the Triangle,
Raleigh, North Carolina