Antimicrobial hand soaps could actually make you more susceptible to deadly staph infections, according to new research published today. Triclosan, the active ingredient in many bacteria-fighting soaps and gingivitis-fighting toothpastes, appears to help the bacteria Staphylococcus aureus, known for its antibiotic-resistant strain called MRSA, colonize human nasal passages. Having those bacteria in your nose isn’t dangerous, or even unusual, if you’re healthy—but their presence can result in serious infections when people undergo medical stresses such as surgery.
The new research, which was led by University of Michigan assistant professor Blaise Boles, found that those with higher levels of triclosan in their nasal fluid were more likely to have colonies of the bacteria. Postdoctoral fellow Sudeshna Ghosh, who worked on the study, told Quartz that this isn’t a case of traditional antibiotic resistance—it’s not just that the triclosan kills weaker bacteria and lets the deadly ones flourish, though other researchers are exploring this possibility.
In fact, triclosan changes S. aureus. “It does something inside the staph cell,” Ghosh says, “and makes it go into a biofilm state.” Biofilms, she explains, are groups of bacteria that work together as a colony. “When it’s cold, and a bunch of penguins gather together for protection from the cold,” she says, “that’s a good analogy for how bacteria can gather into biofilms and protect themselves from outside stress, instead of floating around as individuals.” The biologists aren’t sure why this occurs, and plan to research the relationship between triclosan and bacteria further.
Having a nasal passage coated with bacterial biofilm isn’t inherently bad, Ghosh says: Around one-third of the population has S. aureus in their nose or throat. “Most often,” she says, “it becomes a problem when you go in for a surgery. People with higher colonies have a higher chance of developing infections. So you don’t really want this bacteria living in your nose, even if it usually won’t have any harmful effect.” With a weakened immune system and cuts in the skin, S. aureus can make its way into the bloodstream and cause deadly infections. And around half of the existing strains of S. aureus are now resistant to powerful antibiotics.
“There’s been a lot of research leading up to this,” Ghosh says. “We know now that triclosane isn’t protecting people much when it’s used in soaps.” Indeed, a recent study suggested that the majority of hand washers don’t wait nearly long enough before rinsing the suds away, and miss out on any antimicrobial effects. But we’re still absorbing it through our skin, and it shows up in our bodily fluids. “We’re seeing that it might actually be predisposing us to more infections,” Ghosh says. “We’re seeing that now, and that’s something we should be looking at more closely.”