The US Food and Drug Administration issued an alert Tuesday, February 19, warning older consumers against seeking infusions of blood plasma harvested from younger people. Despite being peddled as anti-aging treatments and cures for a range of conditions, the transfusions are unproven and potentially harmful.

In a statement, FDA Commissioner Scott Gottlieb and the director of FDA’s Center for Biologics Evaluation and Research, Peter Marks, wrote:

Simply put, we’re concerned that some patients are being preyed upon by unscrupulous actors touting treatments of plasma from young donors as cures and remedies.

Establishments in several states are now selling young blood plasma, which is the liquid portion of blood that contains proteins for clotting. The sellers suggest that doses of young plasma can treat conditions ranging from normal aging and memory loss to dementia, Parkinson’s disease, multiple sclerosis, Alzheimer’s disease, heart disease, or post-traumatic stress disorder, according to the FDA.

The claims are wild extrapolations from intriguing but preliminary findings in mouse studies. Over the years, rodent experiments have hinted that components of young mouse blood may invigorate older mice, potentially acting as an anti-aging treatment. However, the results are unclear, controversial, and—most importantly—not proven to have any relevance to human health.

The FDA goes on to note that such infusions are known to pose a range of health risks in humans. These risks include spreading infectious disease, triggering allergic reactions, and causing lung injuries. In some people—particularly those with heart disease—the infusions can also overload the circulatory system, causing swelling and breathing trouble, the agency explains.

Though the FDA didn’t name any infusion companies specifically in its alert, one that has received a lot of media attention is a startup called Ambrosia. It now has locations in Phoenix, Arizona; Los Angeles, California; Tampa, Florida; Omaha, Nebraska; and Houston, Texas, according to the company’s website. Customers 30 years old and above can set up an infusion appointment for plasma harvested from healthy donors aged 16 to 25. A single liter goes for $8,000, while two liters cost $12,000. Neither is covered by insurance.

The company conducted a clinical trial of its infusions in 2016, which wrapped up last year. The trial involved 200 patients aged 35 or older and was said to assess biomarkers in the blood related to aging and certain diseases, including “anemia, neutropenia, thrombocytopenia, obesity, diabetes, high cholesterol, elevated risk of cancer, atherosclerosis, dementia, and cataracts.”

It’s unclear how the trial turned out or if the company had released any of the results. Ambrosia’s website simply states that a trial “studied the benefits of young plasma.”

Ambrosia did not respond to Ars’ request for comment.

In their statement, Gottlieb and Marks added that, if they find any young-blood companies misleading consumers, they were prepared to take “regulatory and enforcement actions.”