The International Space Station is too clean and its making astronauts sick

Astronauts aboard the International Space Station are plagued by persistent rashes, unusual allergies and a variety of infections, including fungi, cold sores and shingles.Researchers now think they know why: The orbiting lab doesn’t have enough germs.Bacteria typically found in or on the body arrive in space with their human hosts, but the array of free-living microbes found on Earth—in soil and water—is lacking.This kind of microbial imbalance has been linked to chronic inflammatory diseases, and scientists hypothesize that cultivating a diverse set of microbes on the ISS—and the station’s eventual replacement—could improve astronaut health.“There’s a big difference between exposure to healthy soil from gardening versus stewing in our own filth, which is kind of what happens if we’re in a strictly enclosed environment with no ongoing input of those healthy sources of microbes from the outside,” said Rob Knight, director of the Center for Microbiome Innovation at the University of California, San Diego.More than 280 astronauts have visited the ISS in its 25-year history, and to better understand the conditions, Knight, other researchers from UCSD and the National Aeronautics and Space Administration worked together to map the microbes living on the space station.The station, they found, is more sterile than living quarters on Earth, and the bacteria they identified there were associated with immune-related symptoms.The findings were published last month in the journal Cell.To map the microbes, astronaut and microbiologist Kathleen Rubins and other crew members swabbed more than 700 surfaces on the space station and more than 60 controls.

Most of the bacteria they found were those that live on humans.Almost none was bacteria normally found in the Earth’s soil and water.“Your immune system needs exposure to a wide range of beneficial microbes from places like soil, healthy animals and healthy plants,” Knight said.

“Understanding whether ...