Most restaurants use commercial dishwashing machines. To clean and sanitize the plates, glasses, and cutlery and dry them quickly, detergents and rinse aids are used. Often, the rinse aid is not washed off with water at the end.

Both the detergents and rinse aids used in such dishwashers contain potentially hazardous substances, and residues could potentially end up in food or drink. However, the effects of detergent and dishwasher residues left on dishware on the cells that line the inside of the intestines have not been well-investigated. The intestinal epithelium barrier controlled by these cells is important for the defense against foreign substances and for the regulation of water and nutrient absorption. Harmful agents, e.g., from detergents could harm this barrier and contribute to diseases.

Ismail Ogulur, Cezmi A. Akdis, MD, Swiss Institute of Allergy and Asthma Research (SIAF), University of Zurich, Davos Wolfgang, Switzerland, and colleagues have investigated the effects of commercial dishwasher detergents and rinse agents on the cells that line the inside of the intestines. The team used cell cultures that mimic human intestinal lining and intestinal cells on microchips for their study. They diluted commercial detergents and rinse aids to reflect the amounts that would be present on dry dishes and then analyzed the effects that these substances have on the cells. They measured cytotoxicity as well as the barrier function of the cells.

The team found that high doses of rinse agents killed intestinal lining cells, and lower doses made the lining more permeable. They also observed the activation of several genes and signaling proteins that could trigger inflammatory responses. A more detailed analysis showed that alcohol ethoxylates present in the rinse aid, in particular, disrupt the barrier integrity. The researchers caution that further studies are needed to show whether the same is true in humans in vivo.

• Gut epithelial barrier damage caused by dishwasher detergents and rinse aids,
  Ismail Ogulur, Yagiz Pat, Tamer Aydin, Duygu Yazici, Beate Rückert, Yaqi Peng, Juno Kim, Urszula Radzikowska, Patrick Westermann, Milena Sokolowska, Raja Dhir, Mubeccel Akdis, Kari Nadeau, Cezmi A. Akdis,
  J. Allergy Clin. Immunol. 2022.
  https://doi.org/10.1016/j.jaci.2022.10.020