The Food and Drug Administration warned Tuesday that a number of businesses are offering plasma transfusions from young donors, saying that there is no proven benefit of such transfusions and that the procedures could be risky.

“We’re concerned that some patients are being preyed upon by unscrupulous actors touting treatments of plasma from young donors as cures and remedies,” FDA Commissioner Scott Gottlieb said in a joint statement with Peter Marks, the director of the FDA’s Center for Biologics Evaluation and Research.