Head to the drugstore to pick up a medication for allergies, insomnia, or migraines, and you might see homeopathic remedies sitting right next to the conventional over-the-counter drugs. But there are important differences between the two. OTC drugs contain active ingredients that the Food and Drug Administration has reviewed for safety and effectiveness. Homeopathic meds are sold without those reviews.

Homeopathy, a centuries-old form of medicine, is based on the theory that “like cures like.” So an allergy remedy might contain Allium cepa (red onion), which proponents claim has a beneficial effect because onions cause irritated eyes and a runny nose, symptoms similar to allergic ones.

Another tenet: The more diluted the “active” ingredient, the greater its benefit. In fact, by definition homeopathic remedies may be so diluted that the helpful ingredient is no longer even detectable.

According to Marvin M. Lipman, M.D., Consumer Reports’ chief medical adviser, these tenets don’t make much sense. “The concepts behind homeopathy defy our understanding of the laws of nature," he says. But sales of these remedies are surging. U.S. consumers spent about $1.2 billion on homeopathic drugs in 2014, according to the Nutrition Business Journal—up 33 percent since 2000. Here, what to know before you buy.

Does Homeopathy Work?

Proponents say that homeopathy can treat many conditions, including asthma and heart disease. Yet this year, after reviewing 176 studies, the National Health and Medical Research Council in Australia found that homeopathics worked no better than placebos, concluding that “there are no health conditions for which there is reliable evidence that homeopathy is effective.”

Why, then, are they so popular? “Some trials done 20 years ago seemed promising,” says Adriane Fugh-Berman, M.D., an expert in botanical medicine and an associate professor of pharmacology at the Georgetown University Medical Center in Washington, D.C. But she says more recent and scientifically rigorous studies don’t support homeopathy.

In an email to Consumer Reports, Alissa Gould, a spokesperson for the American Association of Homeopathic Pharmacists cites a “significant body of evidence that supports the effectiveness of homeopathy,” including a large 2011 report by German researchers. But after evaluating many reliable studies, including comprehensive, independent reviews of the research, Consumer Reports’ medical experts conclude that homeopathic preparations are no more effective than a placebo.

How Homeopathic Meds are Regulated

The FDA classifies homeopathics as drugs. As with other drugs, manufacturers must include a list of ingredients, instructions for use, and at least one medical condition that their product is supposed to treat. Those that are said to treat a serious illness, such as cancer, must be sold by prescription.

But unlike prescription drugs and the active ingredients in OTC products, which are reviewed for safety and effectiveness before they're made available to the public, the FDA doesn’t require makers of homeopathics to submit evidence that their products work or are safe to use. And the agency doesn’t routinely evaluate them. Instead, it requires that homeopathic drugs contain ingredients listed in the Homeopathic Pharmacopoeia of the United States, a database that’s managed by the nongovernmental Homeopathic Pharmacopoeia Convention of the United States.

But that could change. Homeopathy’s rise in popularity is prompting the FDA to examine how the products are evaluated and the Federal Trade Commission to investigate manufacturers’ marketing claims. This past September the FTC held a workshop to evaluate advertising for over-the-counter homeopathic products. The workshop brought together a variety of stakeholders, including medical professionals, industry representatives, consumer advocates, and government regulators. The FTC also invited the public to submit comments on homeopathic marketing.

Homeopathy confusion: This is a picture of a bottle of OTC Excedrin Migraine medicine and homeopathic Hyland's Migraine medicine side by side, showing that it can be difficult to spot the difference between the two products.
Distinguishing homeopathic medicine from real medicine isn't always easy. Look closely and you'll see the word "homeopathic" on one of these.

Confusing Packaging

Some homeopathics look similar to conventional OTC medicines. And because they’re often placed side by side on drugstore shelves, it’s easy for consumers to choose the homeopathic remedy unintentionally.

“It’s misleading and indirectly harmful,” Lipman says. “If you need a decongestant and buy a homeopathic product instead of a real medication, you won’t get relief. Consumers should read labels carefully.”

What’s in Those Products Anyway?

In homeopathic remedies, the active ingredients, usually derived from a plant or an animal, are added to lactose or sugar pills, topical creams, or inhalable liquids. Some might also include questionable substances such as snake venom, arsenic, or other toxic heavy metals.

In March 2014, the distributor Terra-Medica recalled 56 lots (or 1,768 units, according to Terra-Medica president Terry Cotter) of six homeopathic medications distributed by the firm SANUM USA Corp after the FDA found that some might have contained the antibiotic penicillin. Cotter, however, told Consumer Reports that antibiotic residue has never been found in the company’s products.

And in 2010, the FDA warned against giving children Hyland’s Teething Tablets amid concerns that the tablets contained varying amounts of the plant belladonna, also called deadly nightshade. Belladonna can cause a rapid heartbeat, fever, and difficulty urinating. Hyland’s recalled the homeopathic tablets, then reintroduced them in 2011 with a new formula also containing belladonna.

The American Association of Homeopathic Pharmacists dismisses these concerns. Gould says that because homeopathic remedies are so highly diluted “a 10-pound child would have to accidentally ingest, all at the same time, more than a dozen bottles of 135 Baby Teething Tablets before experiencing even dry mouth from the product.” But because homeopathic products aren’t regularly evaluated by the FDA, says Consumers Union programs director and consumer rights advocate Chuck Bell, "The recent FDA recall raises significant safety and quality control concerns.”

This article has been updated to reflect feedback from representatives of the homeopathic industry.