Stormy summer weather may be a more serious threat to those who suffer from bad allergies or asthma.

The term "thunderstorm asthma" was first reported in the 1980s in England and Australia, and cases continue to increase. Thunderstorm asthma describes an attack of asthma that starts or worsens after a thunderstorm. It can occur in anyone with asthma, but it most often affects people with seasonal allergic rhinitis (hay fever or allergies.)

Rain tends to lower pollen counts by cleansing the air, and many people find that rainy weather tends to reduce asthma symptoms triggered by allergies. However, thunderstorms can make asthma worse because of their structure. During a thunderstorm, cold downdrafts concentrate air particles, such as pollen and mold. These air particles are then swept up into clouds where humidity is high. In the clouds, wind, humidity, and lightning break up the particles to a size that can readily enter the nose, sinuses, and lungs, while wind gusts concentrate these small particles so large amounts can be inhaled.

According to a study from the Journal of Allergy and Clinical Immunology, 144 out of 228 people with seasonal allergies reported experiencing thunderstorm asthma, with nearly half of people who had an attack seeking emergency hospital treatment.

Among people with seasonal allergies, risk factors for experiencing thunderstorm asthma include having poorly controlled asthma symptoms, a low score on a rapid exhalation test, higher levels of a certain antibody (ryegrass pollen-specific IgE), higher numbers of eosinophils, which tend to increase when people have allergic conditions, and higher levels of exhaled nitric oxide.

Not everyone with these risk factors will develop thunderstorm asthma, and asthma attacks do not necessarily occur with every storm.

In the US, 25 million people have asthma and more than 20 million have seasonal allergies. It is probable that millions suffer from both conditions, which puts large numbers of people at risk for developing thunderstorm asthma.

Source: Harvard Health