Does Dishwasher Rinse Aid Really Harm Your Gut?

The study making the rounds online was published in 2022 in The Journal of Allergy and Clinical Immunology, a peer-reviewed journal. Scientists at the Swiss Institute of Allergy and Asthma Research (SIAF), part of the University of Zurich in Switzerland, wanted to explore how common dish cleaning products might impact the gut. Specifically, they were interested in epithelial cells, the cells lining the intestines, which are thought to be a key component of the immune system’s defenses.

Researchers washed dishes in both commercial and residential dishwashers and then examined them for residue. They then directly exposed epithelial cells in vitro (outside of the body) to various dilutions of professional rinse aid and other detergents in water to see how they responded. Professional rinse aid was shown to impair epithelial cells after being exposed for 24 continuous hours, and the study pinpointed alcohol ethoxylates as the main culprit.

The study found that cups washed in household dishwashers had undetectable concentrations of detergent, context that social media posts often fail to mention. Instead, the findings being highlighted on social media are from studying residue on dishes washed in commercial dishwashers with professional rinse aid.

Here’s the catch: professional rinse aid is highly concentrated and meant for use in commercial dishwashers. It isn’t rinsed as thoroughly, due to the speed at which dishes must be washed. Commercial kitchens need to sanitize dishes quickly to satisfy health department requirements, and dishes must be dried quickly to keep up with demand. Professional rinse aid makes quick drying possible.

Household dishwashers, on the other hand, have longer cycles and a final rinse of clean water. The rinse aid used in homes is also less concentrated. Because of this, the likelihood of similar amounts of alcohol ethoxylates remaining on your dishes at home is far lower than what might happen in the commercial settings that the experiment was studying.

But whether the dishwasher is commercial or residential, the rinse aid dilutions used in this study do not reflect a manufacturer’s recommended use, noted Joseph Zagorski, a toxicologist and associate professor at the Center for Research on Ingredient Safety, a toxicology research center at Michigan State University. “When used as directed, with the proper dilution, alcohol ethoxylates are considered safe for use. The referenced paper uses dilutions that are outside of the manufacturer’s requirements,” said Zagorski.