Fluoride is everywhere—in plants, soil, even the water we drink. But too much of a good thing can be bad for you.

Excess fluoride increases infants’ chances of developing enamel fluorosis—unsightly spotting, pitting and staining of the outer enamel layer of the teeth—and it poses additional health risks, according to Bill Osmunson, DDS, a dentist in private practice in Oregon and Washington.

The Centers for Disease Control and Prevention and the American Dental Association have warned parents to avoid regularly using fluoridated water to mix infant formula. And a 2006 report recommended that the EPA lower the amount it allows to be added in our water—in fact, Osmunson and many other doctors have joined a movement to stop water fluoridation altogether. “The problem is that some people are ingesting too much fluoride,” he says.

It’s difficult to avoid excess fluoride, but Osmunson offers two simple tips: Buy bottled water, and make sure your children are spitting and rinsing after brushing with fluoride toothpaste.