SACRAMENTO, Calif. — Last September, Vanessa Alvarez had what she thought was a sinus headache she couldn't shake. Then her vision went blurry in one eye.

Within days, the young Elk Grove, Calif., woman was nearly blind from a condition that put pressure on her optic nerve. She and her mother began a quest familiar to anyone who has ever heard the dark slam of the word "incurable."

How to go from zero to expert? How to tell the difference between bold research and brazen scams? Should they go to China? Could stem cells help?

Bogus cures are nearly as old as human disease, but they have found especially fertile ground in stem cell medicine — new, complex and perhaps dazzlingly promising in the long run.

At the University of California Davis Institute for Regenerative Cures, "we're averaging two calls a day from desperate patients," said Director Jan Nolte. On their own behalf, she said, the callers are usually stoic. When they're calling for a child or spouse, they sometimes cry.

"It breaks my heart," Nolte said.

All too often, Nolte must tell those with cancer, those losing their sight, those struggling with disabling arthritis that stem cells can do nothing for them right now. Not in America, and not anywhere else.

She warns anyone who asks, "If a clinic is asking you to pay a lot of money, just really think carefully about what are their motives."

Those who do legitimate research have become increasingly worried about unregulated or even fraudulent clinics.

In July, a journal for kidney specialists described unusual masses that grew in the kidney of a woman given stem cell injections in Thailand. The injections did not lessen her disease, and her kidney had to be removed after it developed tangled growths of bone marrow stem cells and blood cells.

"The world is full of clinics and pseudo practitioners who would offer 'treatments' for conditions that cannot be treated," said Larry Goldstein, director of the UC San Diego Stem Cell Program and a board member of the International Society for Stem Cell Research.

"We are now starting to see reports of people coming back in worse shape than they went," Goldstein said.

The international stem cell group created a website in June that offers tips on how to spot a dubious medical facility, and gives detailed advice on what questions people should ask.

Among the red flags, Goldstein said, are clinics that demand payment for experimental treatments; clinics that don't publish their results in scholarly journals; clinics that claim the same program can treat widely varied diseases; and clinics that claim things rarely or never go wrong.

The society's website is also taking names of clinics around the world that the public would like it to evaluate, and later this year it will begin posting information on how well patient safety is regulated at each of them.

"Everybody loves to believe in the maverick in the wilderness," said Goldstein, who is the author of "Stem Cells for Dummies." ''It's a wonderful myth. It happens sometimes, but it's just not that common."

With stem cells right now, he said, "other than some diseases of the blood, some diseases of the skin and one or two others, there really is nothing else proven to work to a reasonable degree of certainty."