"Walking again - one month after stem cell treatment."

Such is the way that a Swiss clinical center advertises itself online. The institution, with locations in Switzerland, Austria, Serbia, Slovenia, Russia and the US, offers stem cell therapy among other treatments to treat multiple sclerosis (MS).

Nor is it alone in doing so.

Hundreds of private clinics around the world — in developing as well as developed countries — offer stem cell therapies against all kind of diseases.

Whether you're suffering from MS, Parkinson's disease, spinal cord injury or even autism — stem cell therapy, they say, will heal it.

But scientists warn that such promises are deceptive.

There is little or no evidence that those stem cell therapies actually work, researchers said at the science conference Euroscience Open Forumin Toulouse, France.

Worse still, these so-called miracle cures, they say, might actually have harmful side effects that could be deadly.

Big business

It sounds easy: A doctor takes some of your tissue — fat tissue from your hip for example — harvests stem cells out of it in the lab, injects it all back into your body at the appropriate place, and the stem cells do their work to repair damaged body parts.

A very natural way of curing, it seems, and one that has become big business.

In the US alone, about a thousand stem cell clinics have opened up, says Timothy Caulfield, a professor of law and public health at the University of Alberta in Edmonton, Canada.

A treatment normally costs up to $10,000, or roughly 8,500 euros. If multiple interventions are needed — which is often the case, according to Caulfield — the patients can easily pay around $100,000 in total.

But if you're really sick, the treatment's cost is not the primary concern. Getting healed is.

A handful of approved therapies

Most stem cell therapies aren't approved by public health agencies like as the FDA in the US.

"There's interesting research going on, but these things are not really ready for prime time," Caulfield tells DW.

Some therapies are still in clinical trials, while others haven't made it to that point yet.

For some diseases, such as autism, for example, stem cell therapy doesn't even seem scientifically plausible, says Kirstin Matthews of the Baker Institute for Public Policy at the Rice University in the US.

That said, some stem cell therapies do work, of course.

The International Society for Stem Cell Research (ISSCR) has published a list of diseases for which stem cell therapies have already been shown to be effective and safe.

That list is very short, though.

The most prominent example is bone marrow transplantation to treat leukemia or other cancers of the blood. That has proven successful and has been around for decades.

Here, blood or bone marrow stem cells that are either from the patient or the donor are injected into the body — after, for example, the cancer has been eradicated by chemotherapy or radiation.

The injected stem cells start to divide and thus make new immune and blood cells in the body.

The ISSCR lists a few other approved applications, like bone, skin and corneal eye injuries and diseases. "They can be treated by grafting or implanting tissues, and the healing process relies on stem cells within this implanted tissue," they write.

Apart from those specific cases, however, stem cell therapies are purely experimental.

"I don't want to be a downer, I do think we're going to see some stem cell therapies make their way into the clinic," Caulfield says. "But science is hard, and it takes a long time. We need to be patient."

Very risky

Of course, patients can ultimately decide to go for the treatment themselves, even if the scientific evidence is still lacking. If you're going to die, anyway, there's no harm in trying, is there?

But researchers are critical of the fact that many stem cell clinics aren't transparent about exactly what they're offering.

"They are representing these [treatments] as effective, risk-free, and often and increasingly, as routine," Caulfield says. "They are misleading patients in order to get financial gain."

The risk is high that the injected stem cells could start to grow uncontrollably into tumors.

The clinics are not required to register their treatments and report their successes or failures, something they would have to do if they were conducting proper clinical trials.

Timothy Caulfield found, in his studies, that media and social media are helping dubious stem cell clinics to promote their treatments.

"Stem cell therapies are almost always portrayed positively," he says. "The risks and limitations are almost never [mentioned]."

Crowdfunding campaigns also seek to collect money for sick patients to afford stem cell therapies that their health insurance wouldn't pay for.

"A very dominant narrative in that area is that somehow, governments are withholding useful therapies," Caulfield says.

Kirstin Matthews points out that it's for good reason that medical therapies need about 20 years to get approval.

"Twenty years isn't them [the health agencies] looking at a pile of paperwork and ignoring it," she says. "It's actually research that's continuously going on in order to understand that treatment and to figure out what the risks are."

So how can patients make sure they don't become victims of a dubious clinic?

"Always be skeptical," Caulfield warns, "and look for those [treatments or studies] that are associated with a respected research institution."

Plus: Be aware that, if it is a registered clinical trial, you won't have to pay for it.