CAMBRIDGE, Mass. – The unsettling little secret of Zicam Cold Remedy finally spilled out this week. Though widely sold for years as a drug for colds, it was never tested by federal regulators for safety like other drugs. And that was perfectly legal – until scores of consumers lost their sense of smell.

One little word on Zicam’s label explains all this: “homeopathic.”

Zicam and hundreds of other homeopathic remedies – highly diluted drugs made from natural ingredients – are legally sold as treatments with explicit claims of medical benefit. Yet they don’t require federal checks for safety, effectiveness or even the right ingredients.

They’re somewhat similar to dietary supplements, which use many of the same natural ingredients and aren’t federally tested for safety or benefit.

Many scientists view homeopathic remedies as modern snake oil – ineffective but mostly harmless because the drugs in them are present in such tiny amounts.

But an Associated Press analysis of the Food and Drug Administration’s side effect reports found that more than 800 homeopathic ingredients were potentially implicated in health problems last year. Complaints ranged from vomiting to attempted suicide.

In the case of Zicam, the FDA says it tied the drug to reports from 130 consumers who said they lost their sense of smell.

The agency on Tuesday told Zicam maker Matrixx Initiatives to stop marketing three products that carry zinc gluconate: Zicam Cold Remedy Nasal Gel, Nasal Swabs and discontinued Swabs in Kids’ Size. The agency said the drug must be tested for safety and benefit, like a conventional drug, before it is again marketed. And the FDA warned people not to use the three Zicam products.

“It never occurred to me they could be dangerous and there was no kind of oversight – like the FDA – that ensured there was safety,” said former Zicam user David Richardson of Greensboro, N.C. He has complained to the FDA about losing his sense of smell and filed his case with a lawyer for a future lawsuit, joining others who have claimed in recent years that they lost their sense of smell from Zicam cold products.

In its review of homeopathy, the AP also found:

 • Active homeopathic ingredients are typically diluted down to 1 part per million or less, but some are present in much higher concentrations. The active ingredient in Zicam is 2 parts per 100.

 • The FDA has set strict limits for alcohol in medicine, especially for small children, but they don’t apply to homeopathic remedies. The American Academy of Pediatrics has said no medicine should carry more than 5 percent alcohol. The FDA has acknowledged that some homeopathic syrups far surpass 10 percent alcohol.

 • The National Institutes of Health’s alternative medicine center spent $3.8 million on homeopathic research from 2002 to 2007 but is now abandoning studies on homeopathic drugs. “The evidence is not there at this point,” said the center’s director, Dr. Josephine Briggs.

 • At least 20 ingredients used in conventional prescription drugs, such as digitalis for heart trouble and morphine for pain, are also used in homeopathic remedies. Other homeopathic medicines are derived from cancerous or other diseased tissues. Many are formulated from powerful poisons such as strychnine, arsenic or snake venom.

Homeopathy sprang from the inventive – some would say fanciful – mind of German physician and chemist Samuel Hahnemann in the late 1700s. Experimenting on himself, he became convinced that if an ingredient causes a symptom in a healthy person, it will treat the disease that causes the same symptom.

He also theorized that diluting ingredients to minuscule, even untraceable, concentrations paradoxically makes them more powerful.

To this day, homeopaths put forth mystical-sounding explanations involving “vital force” and “healing energy.” And with arcane ingredients, such as “nux vomica” and “arsenicum album,” many homeopathic medicines sound like something brewed in a druid’s kettle.

In 1938, Congress passed a law granting homeopathic remedies the same legal status as regular pharmaceuticals. The law’s principal author was Sen. Royal Copeland of New York, a trained homeopath. “He did it in such a sneaky way that nobody really noticed or paid attention,” medical author Natalie Robins said.

And that law has remained in force ever since.

Almost reduced to obsolescence in the United States, homeopathic remedies have revived in recent decades with the burst of interest in vitamins, herbs and other unconventional treatments. Since 2002, the U.S. homeopathic remedy market exploded by 89 percent to an estimated $830 million last year, according to market research company Mintel. By 2007, homeopathic remedies were taken by almost 4 million Americans, or 2 percent of adults, federal data show.

Pharmacist Albert Lavender, retired deputy director of the FDA’s unit overseeing drug labels, calls it “a big fraud” on the consumer.

“He might not get hurt most of the time, but his pocketbook is getting hurt all of the time,” he said. “It doesn’t make sense” that the FDA requires homeopathic medicine to bear a label saying what it treats, he said, because, in his view, most of it treats nothing.

“Very often, the only active ingredient is alcohol, and patients don’t know that, and they get a buzz-on. The therapeutic effect is no greater or less than a martini,” Dr. Jerry Avorn, an expert in pharmaceutical safety at Harvard Medical School, said.

Richardson said he thought he was taking a government-approved drug when he took a whiff of homeopathic cold gel. He said he felt a burning sensation and hasn’t smelled much since. A doctor who tested his sense of smell tentatively linked his condition to Zicam, Richardson’s medical records show.

Complaints by dozens of patients remain before the courts.

They are highly diluted drugs made from natural ingredients and sold with explicit claims of medical benefit. They are based on a principle unverified by mainstream science: that substances that create certain symptoms in healthy people are effective in treating the disease that causes the same symptoms.

Who makes sure conventional drugs, homeopathic remedies and dietary supplements are made the right way?

The U.S. Food and Drug Administration sets manufacturing standards for both conventional and homeopathic drugs. However, homeopathic products are generally exempt from key requirements, such as verifying the ingredients and the amount used.

As for supplements, the FDA in 2007 adopted manufacturing practices that set broad goals for safety and quality of supplements, which are being phased in through 2010.

Unlike conventional drugs, neither supplements nor homeopathic products are normally required to prove they are safe or effective before going on the market.

Are homeopathic remedies and dietary supplements labeled to say what medical problem they treat?

Homeopathic remedies, like regular drugs, must state what condition they are designed to treat. Bizarrely, the rules are the opposite for supplements, which are forbidden from claiming to treat a specific condition.

What happens when safety problems arise with these alternative treatments?

The FDA can intervene and remove them from the market, as with conventional drugs.

The Associated Press