The woman underwent the $20,000 surgery at a clinic in Beverley Hills in 2009. Surgeons isolated mesenchymal stem cells from her abdominal fat—cells that can become bone, cartilage, and fat, among other types of tissue—before injecting them into the skin around her eyes. The plan was that the stem cells would rejuvenate the skin by transforming into new skin tissue and releasing chemicals that stimulate other skin cells to proliferate.

But the surgeons also injected dermal filler, commonly used to reduce wrinkles. These fillers are made up largely of calcium hydroxylapatite, a mineral used by cell biologists to coax mesenchymal stem cells to become bone. This interaction likely resulted in the development of little pieces of bone in flesh around the woman’s eyes, the surgeon who three months later removed the fragments told Scientific American.

More and more clinics are now offering untested stem cell treatments for a range of cosmetic and medical procedures, and the overstretched US Food and Drug Administration is struggling to clamp down on all of them. Unapproved therapies are dangerous for consumers, and they could also make it more difficult for legitimate stem cell researchers to get funding as unscrupulous private clinics stigmatize the field.