The only scientist to ever walk on the Moon discovers he's allergic to it

The last Apollo mission revealed an unexpected issue that still has researchers stumped decades later: the only scientist to walk on the Moon discovered he was actually allergic to it.

Harrison H. Schmitt was part of Apollo 17, the final crewed mission to the Moon's surface before the program was cancelled. After collecting samples of moon rock from the surface in December 1972, Schmitt returned to the landing module and had an instant allergic reaction when lunar dust from his spacesuit was transferred into the cabin, according to IFLScience .

"First time I smelled the dust I had an allergic reaction, the inside of my nose became swollen, you could hear it in my voice," Schmitt said at the Starmus space festival in 2019, per the Telegraph . "But that gradually, that went away for me, and by the fourth time I inhaled lunar dust I didn’t notice that."

This allergic reaction, dubbed "lunar hay fever," has affected several astronauts exposed to the Moon's surface, according to the European Space Agency , which describes lunar dust as "fine like powder, but sharp like glass."

"A flight surgeon taking suits out of the Apollo 17 command module, after we had splashed down, he had such a reaction that he had to stop doing what he was doing," Schmitt told the conference.

On Earth, dirt and dust is smoothed out by erosion, like water running over pebbles or a constant breeze blowing over a field, NASA explained. But that's not the case on the Moon.

"There is no erosion, so those individual particles end up being very sharp and angular. It is very damaging in ways that we don't see on Earth," Dr. Erica Montbach, project manager of lunar dust mitigation at NASA's Glenn Research Center, said in an article .

The presence of static on the Moon also makes the dust particles easily airborne and able to penetrate deeply into astronauts' lungs.

"We learned from Apollo that lunar dust can be less than 20 microns (about 0.00078 inches) in size," Sharon Miller, the passive dust shedding material program's principal investigator at NASA Glenn, said in an article. "The dust is very fine, abrasive and sharp, like tiny pieces of glass, making it more of a dangerous threat than just a simple nuisance."

Symptoms of lunar hay fever include sneezing to nasal congestion, in some cases taking days for the reactions to fade, according to the ESA.

Researchers are now working on engineering solutions to prevent exposure to lunar dust during future missions, especially since the potential damage from inhaling the dust is unknown.

"Studying the Moon, and eventually Mars, will give us more information about our own planet and the solar system's formation," said Miller. "And when we understand our own planet better, we'll have better ideas about how to protect it for the future."