The plight of a four-year-old boy who nearly died after his parents gave him 12 alternative medicines has prompted doctors to warn against the treatments.
Doctors at Newham Hospital in east London said the parents were "devastated" that their good intentions had made him so unwell. The boy took a dozen supplements supposedly to help treat his autism.
The National Autistic Society said it was crucial for doctors to talk through the risks of alternative therapies.
The boy developed a potentially fatal condition after taking supplements from a naturopath (natural health practitioner) for a number of months, which included vitamin D, camel's milk, silver and Epsom bath salts.
He was admitted to A&E after losing 6.5lbs (3kg) over three weeks, suffering from symptoms including vomiting and extreme thirst.
Dr Catriona Boyd and Dr Abdul Moodambail, writing in the British Medical Journal Case Reports, said it was not until the boy had been at Newham Hospital, which is part of St Bart's Health Trust, for several days that his mother told them about the holistic supplements.
Dr Moodambail told the BBC: "This happens on many occasions with other patients as well.
"Often the parents think that these supplements are natural, safe and do not cause any side effects or adverse effects, but this is not true in many cases like this."
He added: "The situation was stark because the child developed vitamin D toxicity leading to very high calcium levels, making the child quite unwell and this can even be fatal as well."
The boy made a full recovery in two weeks after being treated with hyperhydration and medications to reduce his calcium level.
Dr Boyd and Dr Moodambail's report said they often saw parents turning to alternative remedies to treat children with long-term conditions.
Dr Moodambail said: "This is a common situation because there is no definite curative treatment in some of these long-term conditions such as Autism Spectrum Disorder.
"When some complementary and alternative therapies are suggesting they can cure these situations, these parents get a hope - which is probably a false hope."
The report's authors are recommending that it becomes routine practice to gather information about any complementary treatments being used as part of the history-taking process for all patients.
They said although "families may report benefits with these treatments" there was a problem with the lack of regulation of their use.
In 2010 an Australian report warned alternative remedies can be dangerous for children and even prove fatal if taken instead of conventional drugs.
Jane Harris, director of external affairs at the National Autistic Society, said the case showed how "desperately difficult life can get for families affected by autism especially just before and after receiving diagnoses".
She added: "Most of us know very little about autism until it affects someone we love and it can be hard for individuals and their families to find good, reliable information about autism.
"This leaves many families feeling vulnerable and in desperation - some may consider using unproven and potentially harmful alternative therapies.
"This awful case shows we need more professionals in place to give families accurate advice and talk to them about what really helps and how to find the right support.
"It's crucial that doctors and healthcare professionals take the concerns of families seriously and are able to talk through the potential risks of alternative therapies, even when they might seem harmless."