The Food and Drug Administration is warning consumers that a therapy often marketed for treating autism, cerebral palsy and other conditions is unproven and may “endanger their health.”

Federal regulators said Thursday that contrary to many claims on the Internet, hyperbaric oxygen therapy is not clinically proven to cure or effectively treat the developmental disorders and many other conditions.

“Patients may incorrectly believe that these devices have been proven safe and effective for uses not cleared by the FDA, which may cause them to delay or forgo proven medical therapies,” said Nayan Patel, a biomedical engineer at the FDA’s anesthesiology devices branch. “In doing so, they may experience a lack of improvement and/or worsening of their existing conditions.”

Despite limited research, hyperbaric oxygen therapy has become a popular alternative treatment for autism and cerebral palsy. For the therapy, individuals spend time in a pressurized chamber allowing the lungs to take in as much as three times the normal amount of oxygen.

Hyperbaric oxygen therapy is FDA approved for thirteen different uses including the treatment of thermal burns, carbon monoxide poisoning and decompression sickness that’s sometimes experienced by divers.

But, in issuing the consumer alert this week, regulators listed more than a dozen conditions ranging from autism and cerebral palsy to cancer, AIDS, Alzheimer’s disease and hepatitis for which the therapy is marketed even though the FDA has not approved such uses.

Patel indicated that the agency has received 27 complaints in the last three years from consumers or health care professionals about treatment centers promoting hyperbaric oxygen therapy for uses that are not approved.

Possible risks of hyperbaric oxygen therapy include sinus pain, ear pressure or joint pain as well as more serious problems like paralysis or air embolism, which can obstruct circulation in the body, the FDA said.

This is not the first time a treatment advertised as helping those with autism has been specifically called out by the FDA. In 2010, the agency told eight businesses to stop marketing chelation products to those with autism and other conditions citing serious side effects including death.