It started simply enough – with suggestions that her child should follow an unremarkable-sounding special diet. “They did these tests: a stool test and a urine test,” Layla (not her real name) tells BuzzFeed News. “I can’t remember where they were from – not the NHS, obviously, but some lab. The results had all these red markers.” The tests, from an alternative medicine practitioner who was recommended by and paid for by a major charity, apparently showed that Layla’s son, an autistic boy who was 3 at the time, had various issues with his gut and his metabolism. “I was shocked,” says Layla. “I didn’t realise – my son had all these deficiencies, these toxins in his system.”

The tests recommended a gluten-, casein-, and dairy-free diet. “It didn’t seem like a really big deal,” says Layla. “I thought, gluten, it’s bread and pasta – it’s not a massive thing.” The practitioner told her to monitor her son’s sleep and behaviour, and to expect improvements in the symptoms of his autism if they followed the diet.

But that’s not all she told Layla. “In the first hour, she told us that there was a lot of science and research that proves that autism is caused by vaccines,” she says. “She said if the child has lots of bugs as a baby, ear infections, and antibiotics, it crashes their immune system. Vaccinations cause them to regress. MMR [the measles, mumps, and rubella vaccine] is the final thing that causes them to regress into autism.”

From there, the practitioner tried to lead Layla and her son down a rabbit hole of weirder, more intrusive supposed treatments for autism. “She asked me to join a forum, a Facebook group,” says Layla. Facebook groups and, in earlier years, internet chat groups have been a vital source of support for parents of autistic children. But they have also been a key recruiting ground for quacks and charlatans, preying on parental desperation.

The group Layla joined recommended “biomedical” treatments – which included gluten-/casein-free diets, but also supplements, vitamin B12 injections, and, alarmingly, “GcMAF” or “Rerum”, a dangerous stem-cell treatment that the Medicines and Healthcare Products Regulatory Agency (MHRA) calls “a significant risk to people’s health”.

Her practitioner also mentioned “chelation” – a potentially dangerous method of using chemicals to remove heavy metals from the bloodstream – and she was aware of another Facebook group pushing “Mineral Miracle Solution” (MMS), a much-hyped cure-all substance that is in fact a form of chlorine-based bleach, often given as an enema.

“Some of [the group members] were doing lots of supplements, going to doctors in the US, being told all this stuff, sometimes for a number of years,” says Layla. “It was overwhelming. It took a while for the penny to drop, but then I realised I couldn’t believe the stuff that was going on. I just started to question it, to question what they were doing.”

Layla’s story is not unusual. Pseudoscientific treatments exist for almost all diseases and conditions, but parents of autistic children seem to be disproportionately targeted by quacks and snake-oil peddlers, according to parents and experts spoken to by BuzzFeed News.

“The targeting of parents who have recently diagnosed children is very insistent,” says Sarah-Jayne Garner, a mother of an autistic son and campaigner for autistic rights, who is herself autistic. “It’s constant. The first thing anyone says to you is ‘Get them on a gluten-free diet.’ It’s not backed up by any kind of serious science, but parents who are new to autism just don’t have the tools and knowledge to assess what’s being presented to them as solutions to what they’re told are their problems.”

There are hundreds of websites and Facebook pages that claim that autism is caused by vaccines, and which promote “cures” – often substances that can be bought via that website. And the stories they share are often hugely viral.

Analysis by BuzzFeed News found that more than half of the most-shared scientific stories about autism published online in the last five years promote unevidenced or disproven treatments, or purported causes.