What is thunderstorm asthma?

CHICAGO (WGN) — Think of it as the perfect storm: High grass pollen counts combined with the high energy of a spring storm can create a formula that leads to deeper problems than just itchy eyes and sneezing.

Doctors issue a warning: Watch out for thunderstorm asthma. With everything already in bloom, spring allergy counts remain at high levels.

“When we look around at all the trees, there are little catkins or things hanging from the trees, and that is what produces pollen...