Homeopathic remedies, unlike most medical therapies, have never been effectively regulated by the Food and Drug Administration (FDA)—until now.

On Dec. 18, FDA officials announced plans to limit the sale of certain homeopathic products. Specifically, products that contain dangerous ingredients, products administered by unusual routes, such as injection, products claiming to treat life-threatening conditions, and products for vulnerable populations, such as infants, children, the elderly, and pregnant women.

"In many cases, people may be placing their trust and money in therapies that bring little to no benefit," said FDA Commissioner Scott Gottlieb. "Worse, [these products] may cause significant or irreparable harm."

The FDA's proposed policy will be open for public comment for 90 days.

Although the FDA hasn't regulated homeopathic remedies since the passage of the Food, Drug, and Cosmetics Act in 1938, times have changed. During the past decade, the market for homeopathic products has increased exponentially; it's now a $3 billion a year industry.

Safety problems have also increased. For example, Hyland's Teething Tablets, a homeopathic remedy for babies, was found to contain undeclared quantities of belladonna, which can cause seizures, coma, and death. Intranasal cold preparations containing zinc have caused anosmia—a loss of smell. And a homeopathic product called nux vomica, which is made from a tree native to India, contained strychnine, a well-known rat poison.

Ironically, some of the homeopathic products that the FDA has chosen to regulate aren't really homeopathic. To understand why, we need to go back to the beginning.

Homeopathy was the brainchild of Samuel Hahnemann, a physician who practiced in Germany and France between 1779 and 1843. Hahnemann had tired of the brutality of eighteenth century medicine, which included bloodletting with leaches, skin blistering with acids, and medicines that induce vomiting (emetics) or diarrhea (cathartics). In 1790, he believed he had found an alternative. While ingesting quinine, Hahnemann developed a fever. He reasoned that because quinine was a known treatment for malaria, and because malaria also caused fever, medicines should induce the same symptoms as the disease that they're treating. (The word homeopathy literally means "similar suffering.") He called his idea "like cures like."

Hahnemann knew that "like cures like" was going to be a difficult sell. So he created the second principle of homeopathy: "the law of infinitesimals." Hahnemann diluted emetics and cathartics again and again until not a single molecule of the original ingredient remained. If the active ingredient was diluted in water, then the final product was water. Hahnemann believed that although the active ingredient was gone, the water would remember that it had been there.

Hanhemann's "law of infinitesimals" lives on today in homeopathic products such as Oscillococcinum. Billed as "Nature's No. 1 Flu Remedy," Oscillococcinum is made by taking the liver and spleen of a duck, homogenizing it, diluting it 1:100 in water, then repeating the 1:100 dilution two hundred more times. In the final preparation, the duck's liver and spleen are gone.

Costing about $3 per tablet, Oscillococcinum, for all practical purposes, is one gram of sugar. Its value — if there is any value at all — comes from people believing that it's working, a response also known as the placebo effect.

Oscillococcinum won't be affected by the new FDA guidelines. Rather, the FDA's main focus will be on products that contain undeclared levels of active ingredients that could cause suffering or hospitalization or death. Because these products contain active ingredients, they aren't really homeopathic.

But real homeopathic remedies can also be harmful, especially if consumers think that they're treating serious disorders like asthma, cancer or opioid addiction when they're not. By embracing homeopathic remedies for life-threatening situations, consumers sometimes reject drugs that really could help them.

Hahnemann wanted to create medicines that were kinder, gentler, and safer than the medicines of his time. One can only imagine that had he had insulin to treat diabetes or chemotherapies to treat cancer he wouldn't have invented homeopathy. By cracking down on homeopathic products, the FDA is finally holding these modern-day snake oil salesmen accountable. The consumer can only benefit.

Paul A. Offit, MD, is a professor of pediatrics at the Children's Hospital of Philadelphia and the author of the forthcoming book 'Bad Advice: Or Why Celebrities, Politicians, and Activists Aren't Your Best Source of Health Information.'