Drinking “raw water” is now a thing.

In the age of Flint, Mich., and other lead contamination reports, fluoride deniers, and pollution concerns, some companies are now touting the benefits of drinking untreated spring water.

The water is purported to help keep the bacteria in your gut balanced, rejuvenate your skin, and heal maladies such as arthritis and kidney disease. But before you buy into the latest health craze, know that drinking raw water can — like an earlier fad for raw milk — present serious health risks.

“Don’t,” said Charles Haas, a professor of environmental engineering at Drexel University. “You don’t know what is being fed into the streams in terms of potential sources of pollution.”

Municipal tap water in the United States is high quality and does not pose risks to human health, Haas said.

“And it is far cheaper,” he said.

Live Water, a company that markets the “raw” liquid in clear glass jugs, offers water from an “ancient aquifer” delivered to doorsteps in the San Francisco, Los Angeles, and San Diego areas. A 2.5-gallon jug costs $16, with a $22 deposit. The company promises water with healthy probiotics and no harmful contamination.

Tourmaline Spring of Harrison, Maine, will send you 12 one-liter bottles for $35.95 plus $23.75 shipping. Its website says its product is “completely exempt from all processing requirements because of its natural purity.”

But even the most pristine-looking streams can be vulnerable to agricultural and animal pollution. Think of what might be out of sight in the water, Haas said.

Which brings us to “beaver fever.”

Also known as Giardia intestinalis, “beaver fever” is a familiar name to hikers who become sick after drinking unfiltered water from country streams, Haas said. It is an intestinal infection caused by microscopic parasites usually found in fecal matter from infected animals or humans and can result in abdominal cramps and diarrhea, according to the Centers for Disease Control and Prevention.

Even rainwater should be cleaned before it is used as a drinking source, Haas said. Though it may be relatively clean as it falls, once it hits a surface, it gets mixed in with whatever it touches, such as dust or animal debris.

“You pick up all sorts of chemical and microbiological contaminants,” Haas said.

According to the CDC, U.S. water disinfection and chlorination is among the 10 greatest public health achievements of the 20th century. In 1908, Jersey City, N.J., was the first city in the U.S. to begin routine disinfection of community drinking water. Diseases like cholera and typhoid dropped significantly once cities began cleaning and treating water, the CDC reported.

“Clean water has made such a difference in people’s life expectancies in the United States and other industrialized countries, so I can’t imagine why you would want to drink water that wasn’t and thereby endanger your health,” Michelle Francl, professor of chemistry at Bryn Mawr College, told the Washington Post.