Thunder fever sounds fake, but it’s a real danger to asthma sufferers

When spring and summer storms strike, asthma attacks can get worse.

Last week a bizarre and ominous term surfaced online: thunder fever. The term refers to the idea that certain thunderstorm conditions put people with asthma at an increased risk of an attack; far more so than during any other weather pattern.

Is thunder fever real?

No scientific journal actually references the term itself, but the underlying idea appears to hold some truth: Certain conditions during thunderstorms generate massive amounts of tiny pollen particles that pose a danger to asthma sufferers.

Many of the handful of studies looking into this phenomenon came about from an observation that during a thunderstorm, the number of doctor’s office and emergency room visits for asthma attacks seem to go up. One study found an uptick in the number of asthma emergency room events between June 24th and 25th, 1994 at the St. Mary’s Hospital in London—the exact same time that a huge thunderstorm event occurred. Doctors and hospitals have reported similar events in Italy and Australia.

The most comprehensive study looking into the phenomenon is a 2008 analysis published in the respiratory medicine journal, Thorax, which examined the thunderstorm and asthma relationship in Atlanta, Georgia.

What causes this?

All studies, including the one in Thorax, seem to agree on the same mechanism: At the beginning of a thunderstorm, a huge updraft carries air particles containing pollen upward to the waterlogged cloud layers. There, this sudden change from dry to super-humid air causes the wind-carried pollen grains to rupture, creating a profusion of tiny allergen particles in the sky. Then, the thunderstorm’s downdraft of gusty wind carries those particles back to the air we breathe.

When someone with asthma inhales those bits of pollen, this can trigger an attack. And because of the huge abundance of these tiny particles, these attacks have the potential to be life-threatening.

The prevalence is still not entirely clear as most studies done on the bizarre association have been limited; each one was more or less a case study—examining one thunderstorm event and the number of asthma-related events that followed. The 2008 Thorax study collected data from over 10 million emergency department visits from 20 hospitals between 1993 and 2004. They cross-referenced that data with weather information collected over that time period. In total, they were able to look at 564 thunderstorm days. The researchers observed a statistically significant association between asthma emergency room visits and thunderstorm occurrences; in other words, the number of times an asthma emergency room visit occurred in conjunction with a thunderstorm couldn’t be attributed to random chance alone. “Overall, asthma visits were three percent higher on days following thunderstorms,” the researchers write.

Those associations only held when the thunderstorms were associated with rainfall and were “strongest when wind gusts were intermediate and high”—which supports the hypothesis that rain and wind help to carry the broken pollen bits back down to ground level, where we breathe.

Should I be worried?

The most troubling part of this phenomenon, the researchers say, is that these tiny particles can get stuck in people’s lungs, which could cause even non-asthmatic people to experience breathing issues. But it’s still far more dangerous for people with asthma-related disorders. In a 2013 study reviewing this condition, allergists found that people who had a pollen allergy and stayed indoors with their windows closed during the thunderstorm did not experience symptoms, and that asthma attacks were far worse for people who weren’t taking medication to control their asthma and allergies. So finding an allergy and asthma medication mix that works for you—and, when possible, staying inside during thunderstorms—can help keep you safe.