A new UC Davis study shows that a common antibacterial chemical added to bath soaps can alter hormonal activity in rats and in human cells in the laboratory—and does so by a previously unreported mechanism.

The findings come as an increasing number of studies – of both lab animals and humans – are revealing that some synthetic chemicals in household products can cause health problems by interfering with normal hormone action.

Called endocrine disruptors, or endocrine disrupting substances (EDS), such chemicals have been linked in animal studies to a variety of problems, including cancer, reproductive failure and developmental anomalies.

“This finding may eventually lead to an explanation for some rises in some previously described reproductive problems that have been difficult to understand,” said one author, Bill Lasley, a UC Davis expert on reproductive toxicology and professor emeritus of veterinary medicine. More analyses of antibacterials and endocrine effects are planned, he said.