Associate Editor
Surfer scratching head.

It only takes 10 minutes in the ocean for your skin’s microbiome to change. Photo: Oliver Sjostrom

The Inertia

It’s easy to get poetic about the pleasures of getting a morning surf during the week before taking on the work (or school) day. And in our quest to squeeze ocean time into busy schedules, that often means settling for a post-surf rinse at your local’s showers or, worst case, just heading straight to work after an abbreviated morning session. But according to a preliminary study out this week, it only takes ten minutes for your skin to be covered in ocean bacteria, altering your skin’s microbiome.

“Our data demonstrate for the first time that ocean water exposure can alter the diversity and composition of the human skin microbiome,” explained Marisa Chattman Nielsen, MS, a Ph.D. student at the University of California, Irvine, and lead author on the study. “While swimming normal resident bacteria were washed off while ocean bacteria were deposited onto the skin.”

In their preliminary research to be presented at the American Society for Microbiology’s annual conference this week, Nielsen and fellow researchers from UC Irvine took nine volunteers that each met specific criteria (including not having taken antibiotics in the last six months), and swabbed their calves before a ten-minute swim in the ocean, immediately after air drying, six hours later, and 24 hours later. The research team detected ocean bacteria on all participants after six hours and 24 hours – although some acquired more bacteria than others.

Each participant, the study notes, had a unique microbiome “community” on their skin, but after swimming, each appeared very similar. By 24 hours, though, each person’s microbiome had largely gone back to normal.


It’s worth noting that not all bacteria are bad, but one finding was a little troubling. On all nine participants, researchers detected ocean-dwelling Vibrio bacteria. Most Vibrio species are harmless, but some do cause cholera or other serious ailments.

“While many Vibrio are not pathogenic, the fact that we recovered them on the skin after swimming demonstrates that pathogenic Vibrio species could potentially persist on the skin after swimming,” said Nielsen.

The study shouldn’t preclude anyone from surfing or otherwise enjoying the ocean, but it does make the case for showering afterward.


“Recent studies have shown that human skin microbiome plays an important role in immune system function, localized and systemic diseases, and infection,” said Nielsen. “A healthy microbiome protects the host from colonization and infection by opportunistic and pathogenic microbes.”


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