Since 2015, a Texas company has been charging customers between $100 and $250 per session to be hooked to an IV of vitamins and herbs to treat diseases like cancer, multiple sclerosis, and congestive heart failure. But there is a problem: there is no proof they actually work.

IV therapy has been featured on health websites like Gwenyth Paltrow’s GOOP for its hydrating and anti-aging benefits. But the Federal Trade Commission said Thursday that companies are not allowed to make unsupported promises about the therapy’s effectiveness when it comes to treating diseases.