The ISS May Be Too Clean For Its Own Good!

With advanced air filters and strict cleaning routines, the International Space Station (ISS) is one of the cleanest places beyond Earth. Yet astronauts often experience a range of health issues while aboard. A new study suggests that one reason may be that the ISS is too clean!

For their research, Rodolfo Benitez and his team at UC San Diego asked astronauts to wipe different parts of the ISS to collect samples. This included the kitchen, bathroom, and eating area. Over 800 samples were collected and sent back to Earth for analysis.

The results showed a lack of "good" environmental microbes. These are the kind typically found in soil, water, and plants on Earth. The only microbes present were human-related. They included bacteria from the astronauts' skin and the food they ate. Also, though cleaning had been stopped a few days before the samples were taken, the swabs showed high levels of chemical residue.

The researchers suggest that the lack of diverse microbes and the constant cleaning may cause the immune system to struggle to function normally. This could explain why astronauts often experience cold sores, skin rashes, and other issues while in orbit.

The study's findings were published in the journal Cell on February 27, 2025. They are particularly important for future missions to the Moon and beyond. To ensure astronauts remain healthy, scientists will have to find ways to bring "good germs" into the mix. This could be done by bringing animals or plants aboard the spacecraft.

"The reality is that we’re going to inhabit space at some point, so this work will give us the first insight in terms of the things that we need to add and remove," says Pieter Dorrestein, a biochemist at UC San Diego. "The most important message that we can pass on is how important it is to not only look at what’s present but also what’s absent."

Resources: Phys.org, Sciencenews.org, Smithsonianmag.com