Anne Borden King remembers the day a developmental pediatrician diagnosed her son Baxter with autism.

"It was a frightening conversation," she said. "I think a lot of people walk out of that appointment going, 'I've got to do everything. I've got to stop it. I'm going to throw everything I can at the autism.'"

It's that fear, Borden King thinks, that prompts many parents to try anything that offers hope of treating their child's autism — even if there's no scientific evidence to support it.

Anne Borden King filed a third-party complaint with the College of Physicians and Surgeons of Ontario against a medical doctor who practises chelation therapy for children with autism. Her complaint was dismissed. (Craig Chivers/CBC )

She and her husband took a conventional approach to dealing with Baxter's autism, including working with therapists and teachers to improve his communication and motor skills. Now eight years old, Baxter is talkative and playful. His parents use recognized coping strategies, including limiting bright lights and large crowds, that can be overwhelming to someone with autism.

There's no known specific cause for autism, but current research increasingly suggests there are genetic factors involved. Researchers are also looking at whether there are possible environmental triggers.

Still, parents are faced with a dizzying array of treatments — some based on old theories that have been disproven — that they learn about online and from talking with other families. Borden King, who formed an autism advocacy group, became alarmed when she heard parents talking about chelation therapy.

Chelation is a treatment used to remove heavy metals, such as lead or mercury, from the body. A drug that "grabs" the metals is administered to the patient, often intravenously. Then the patient excretes them, usually through their urine.

Chelating drugs are approved by Health Canada to treat heavy metal toxicity, which could occur if someone were in an industrial accident, or suffered mercury or lead poisoning. The notion of using chelation as a treatment for autism originated years ago, when some people believed there was a link between autism and mercury contained in childhood vaccines.

But no such link was ever found, and autism experts widely agree that the idea of chelation therapy helping to treat autism has no scientific merit.

"Chelation is a treatment for which we have no evidence of benefit and we have evidence of harm," said Dr. Evdokia Anagnostou, a pediatric neurologist and senior autism researcher at Holland Bloorview Kids Rehabilitation Hospital in Toronto.

Pediatric neurologist and autism expert Dr. Evdokia Anagnostou says she's fine with parents trying some types of alternative treatments for their children, but she draws the line at chelation therapy saying it's dangerous. (Oliver Walters/CBC)

Parents often discuss alternative treatments they're considering for their children with autism with Anagnostou, and she's fine with many of them as long as they're safe and used in conjunction with proven autism interventions. But she draws the line at chelation therapy.

It's dangerous, she said, because while metals are being removed from the blood, mineral concentrations change quickly and can cause "metabolic abnormalities." Those can damage the heart and kidneys, and even result in death. Two cases of children dying from chelation therapy for autism have been reported in the scientific literature, Anagnostou said.

'Wild west'

So when Borden King found out that Dr. John Gannage, a physician in Markham, Ont., was offering chelation therapy to children with autism, she called government agencies to try to find out if there were any clear regulations preventing that — and found there weren't.

"It's this Wild West," she said. "There is no law that says that you can't do these things."

One of the officials she spoke with advised her to file a complaint with the College of Physicians and Surgeons of Ontario, the body that regulates medical doctors in the province. She did, and in July received a response saying the college was satisfied Gannage was acting in accordance with its policy on complementary/alternative medicine.

"Increasingly, patients are looking to alternative treatments and many physicians have incorporated these complementary therapies into their practices," said college spokesperson Shae Greenfield in an emailed statement to CBC News.

"Although the [college] does not take a position on individual therapies or treatments, we have developed policies to guide physician conduct while supporting patient autonomy. If physicians offer complementary treatments to patients, their diagnosis must be based on their clinical assessment, be supported by sound clinical judgment and informed by evidence and a risk-benefit analysis.

"If patients have concerns about the care or treatment they've received, we encourage them to contact our public advisory service."

Autism specialist Dr. Wendy Roberts says chelation therapy costs parents a lot of money that could otherwise be used on proven treatments, including communication and behavioural therapy. (Craig Chivers/CBC)

The college's response to Borden King noted that she had never personally met Gannage, "nor does she have any patient-specific information."

In Gannage's response to the complaint, obtained by CBC News, he said chelation was a "small component" of his work with children who have "complex" and severe autism, and that he gets "full consent" from parents, "including clear communication that it [chelation therapy] is not standard practice."

"I have never harmed a child with my treatments, yet believe that leaving behind damaging toxic metal burdens when I have the means to intervene, during a critical window of opportunity, is potentially harmful with long-term negative consequences," Gannage said.

Gannage did not respond to CBC's requests for an interview.

CBC News asked the college whether the fact that Gannage practised chelation therapy for autism, given that autism experts have said there is no scientific basis for it, meets its requirements for treatments to be informed by evidence. The college said it could not comment on the specific case, because Gannage had been cleared of wrongdoing.

Don't delay proven techniques

The lack of clear guidelines around the use of chelation therapy for autism appears to be an issue across the country.

In an emailed statement, Health Canada said it "has not authorized any chelation therapy drugs or natural health products for use in children as treatment for autism."

However, physicians can use their "medical discretion" to prescribe drugs "off-label" to patients for conditions for which the medication wasn't approved.

"This falls within the practice of medicine, which is regulated provincially and territorially by the various professional colleges," Health Canada's statement said.

In addition to the risk of harm, another big concern experts have is the fact that chelation therapy, which is not covered by drug plans for autism, requires parents who may have limited financial resources to pay a lot for an ineffective treatment.

When parents choose to spend their money on something like chelation therapy for their children, they often "put off, for sometimes months at a time, getting the kind of intensive social, communication and behavioural support that they need, which is [also] expensive," said Dr. Wendy Roberts, a Toronto-based developmental pediatrician specializing in autism.

"Delay in [proven] intervention is the single most important thing not to have happen when you get a diagnosis of autism," she said.

Watch CBC's full news report on chelation therapy: