The short answer is no. Toxins have not been shown to cause autism.
The longer answer is that approaches to autism that seek to repair non-existent 'toxicity' are heavily marketed, despite having no evidence of efficacy and being dangerous to those receiving those treatments.
We reviewed the evidence for 'leaky gut' in autism and found it false. We reviewed the idea that autistic folk have detectible levels of 'toxins' in their brains or blood, and found it false.
The Association for Science in Autism Treatment (ASAT) has published a succinct survey of what is known about the causes of autism:
At this time, the exact cause of autism remains uncertain, but research suggests that any one of several factors may be involved in its onset: genetic factors, possible environmental influences; certain types of infections; problems before, during, or after birth. Some studies suggest the possibility of a disruption of very early brain development, before birth.
There is extensive past and ongoing research intending to delineate the causes of autism.
Increased frequency of occurrence of autism within families supports a probable genetic contribution to the disorder; however, it is very unlikely that any one single genetic defect will explain all cases of autism. Observations that the identical twins of an individual with autism has only about a 60% chance of also having autism, lead to the conclusion that genetics alone do not explain the condition. Ongoing research is seeking to find out if a genetic predisposition to autism may be triggered to develop into autism by the occurrence of certain environmental, infectious, immunological, and other conditions or events.
At this time, there is no evidence that specific toxins in the environment, immunization practices, dietary differences, or immunologic differences cause autism. It is quite likely that some combination of genetic, neuropathologic, and environmental agents will explain the etiology of autism, and that the etiology may vary from one individual to another.
Nonetheless, there are people who believe that autism is caused by 'toxicity', which can be diagnosed using various urine, blood, stool, and hair tests; the problems the tests reveal can be addressed by various treatments. People holding this set of beliefs are roughly referred to as the "autism biomedical movement. "
The invalidity of one type of tests has been discussed in depth by Stephen Barrett MD in How the "Urine Toxic Metals" Test Is Used to Defraud Patients
Physician-researcher David Gorski MD wrote, about "biomedical autism treatments"
These ideas are dangerous because they have direct consequences for children with autism. These consequences take the form of subjecting children to unscientific treatments that are ineffective at best and harmful at worst, sometimes even life-threatening....
Autistic children have paid the price. They will continue to pay the price until somehow, some way, science-based medicine, rather than anecdote- and pseudoscience-based medicine can prevail. Autistic children deserve no less than the best scientific medicine that can be brought to bear on helping them to develop and alleviating their symptoms. They most certainly don’t deserve the unethical and uncontrolled experimentation to which far too many of them are being subjected.
Matt Carey pointed out that the autism biomedical industry is entirely unregulated and does not even collect data on adverse reactions to biomedical treatments.
.....are people being given the ability to make an informed decision about alternative medical treatments used for autism? The answer is simple as well: no. They are not.
Back in 2009, the blog Left Brain / Right Brain published a list of biomedical autism treatments as seen through the postings of one family.
But behind the scientific and legal consensus that vaccines do not cause autism lies a hidden world, the autism “biomedical” yahoo- and chat-group world. There is no decline in the number of posts in this world. It’s a thriving, and growing community, one that has fueled the popularity of the anti-vaxers, and the certainty of those parents who consider their child “vaccine-injured”. It has spurred the spending of millions of dollars on supplements, hyperbaric treatments, off-label prescription medications, and myriad other autism “biomedical treatments”. These “treatments” are almost all of no proven benefit, some are ridiculous, some relatively benign, and many potentially dangerous. This article will explore the journey of one mother, “Mary” in her efforts to cure her son “Saul”. While the case of Mary and Saul, documented in her own words is shocking and appalling, Mary is not alone nor is she an extreme case. She is one of thousands of parents seeking autism “biomedical treatments” on the internet.
The Autism Science Foundation has published a non-exhaustive list of such treatments
Biomedical Non-Evidence-Based Treatments
Chelation: Chelation therapy involves administering chemicals designed to bind to heavy metals and eliminate them from the body. Chelating agents have a legitimate use in the treatment of poisoning from lead, mercury and other metals. There is no evidence that supports chelation as a safe treatment alternative because autism is not caused by metal poisoning. In 2005, a child with autism died from chelation therapy, when the chelating agent bonded with calcium in his body and caused his heart to stop. No paper published in the peer-reviewed literature has reported abnormal levels of mercury in individuals with autism spectrum disorder. Moreover, symptoms of mercury poisoning are unlike symptoms of autism, making chelation an impractical way to improve symptoms.
Lupron Therapy: Lupron is a testosterone-inhibiting drug used in the treatment of precocious puberty (which is rare) and prostate cancer, as well as for the “chemical castration” of sex offenders. Its use for autism is based on the hypothesis that testosterone magnifies the toxic effects of mercury (see above). There is no evidence that Lupron is safe or effective for the treatment of autism. In addition, it can have harmful side effects including hives, difficulty breathing/ swallowing, numbness, tingling, weakness, painful or difficult urination, blood in the urine, bone pain, testicular pain and osteoporosis.
Hyperbaric Oxygen Therapy (HBOT): HBOT has been proven effective for treatment of gangrene, carbon monoxide poisoning, “the bends” and various other conditions related to oxygen in blood. There is no evidence to support ASD as an insufficiency of oxygen in the blood. Evidence also fails to support HBOT as safe or effective for the treatment of autism. Furthermore, the benefits of hyperbaric oxygen delivered in a soft-shelled chamber are no different than with a less expensive oxygen tent, or nasal cannula.
Gluten Free-Casein Free (GFCF) Diet: Those who promote gluten (protein found in wheat, rye, and barley products) and casein (protein found in dairy products) free diets claim that children with autism have "leaky guts" that allow opioids to escape into the bloodstream and then travel to the brain and cause autistic behaviors. There is no evidence for this claim, and studies have found that compared to typically developing children, children with autism have no more opioids in their blood. Furthermore, children on the GFCF diet have been found to have lower bone density than controls, which could lead to osteoporosis. A large-scale study of the safety and efficacy of the GFCF diet indicated that children on the diet had similar outcomes to those who were not on the diet.
Stem Cell Therapy: Stem cell therapy for autism is illegal in the United States, but that hasn’t stopped some from offering this as a treatment for autism in Costa Rica, China, and other countries. There is no evidence that the treatment is safe or effective for autism, and no guarantee that the stem cells used in these countries are even human.
Secretin Injections: Secretin is a hormone that controls digestion. It is currently prepared from pigs as a synthetic human form is not available. The FDA has approved use of single doses of secretin in diagnosing gastrointestinal problems such as ulcers or impaired pancreatic function in adults, but it has not formally approved the hormone for autism treatment. No data exists on the safety or efficacy of repeated doses of secretin or its use in children. In a report, the National Institutes of Child Health and Human Development states that the efficacy of secretin in ASD treatment is currently unknown.
Antifungal Agent Therapy: Some people believe that bacteria in the gut cause autism, and since antifungal medications can eliminate bacteria they believe they can simultaneously cure autism. There is no evidence to support any antifungal agent as an autism cure. Importantly, treating children with antifungal agents is potentially harmful; possible side effects include itching, irritation, burning, diarrhea, stomach pain, and skin rashes. Some antifungal treatments, including Diflucan, Sporanox, Lamisil, and Nizoral, are absorbed in the body and can impede liver functioning over time.
Vitamin Supplements: It is important to maintain a healthy and balanced diet. To achieve this goal, healthcare providers may recommend nutritional supplements to people with and without autism. Use of supplements can be problematic however, when they are misused in an attempt to cure an individual of autism. There is no scientific evidence suggesting that vitamin supplements can cure autism. Using supplements without consulting a healthcare provider can be dangerous. Some supplements (e.g., vitamin A) can be toxic when taken in high doses for sustained periods; others may not contain what they claim.
Raw Camel Milk: Raw camel milk has been alleged to cure autism-related ills with benefits ranging from improved eye contact and motor skills to decreased inflammation. Although it may be nutritious, there is no scientific research that upholds claims that raw camel milk is an autism “cure-all.”
Marijuana Therapy: Marijuana is an illicit drug whose use in ASD treatment is neither medically nor scientifically supported. Reported short-term side effects of marijuana use include distorted perception; impaired coordination; and impaired thinking, problem solving, learning and memory. Long-term marijuana use has been associated with decreased learning abilities, increased risk of respiratory diseases associated with smoking, and decreased motivation.
Nicotine Patch Therapy: Research studies have uncovered abnormalities in nicotinic acetylcholine receptors in the brains of people with autism, and some scientists have posited that core symptoms of ASD could be attributed to these alterations. Some findings specifically indicate a shortage of these receptors, leading some to believe that stimulating or increasing these receptors could eliminate ASD symptoms. Proponents of nicotine patch use in individuals with ASD believe that the nicotine released into the body from the patch activates and upregulates receptors, and thereby reduces ASD symptoms. Despite having a rationale that is based on scientific findings, use of this treatment is not supported by scientific evidence. No clinical trials have demonstrated that nicotine patches are safe or effective in the treatment of ASD. Common side effects reported in clinical studies evaluating safety and efficacy of the patches include skin irritation; sleep problems, including insomnia and nightmares; headaches, indigestion, and nervousness.
Bleach Therapy: In bleach therapy, an individual with ASD is given a diluted form of bleach orally or through an enema in an attempt to cure their symptoms. Bleach doses are given repeatedly; supporters of this treatment have recommended that children drink the bleach mixture up to eight times per day or receive an enema up to three times per week. The rationale for the treatment is that bleach can eliminate bacteria, parasites, yeast, and heavy metals and consequently eliminate ASD symptoms. This treatment has been widely denounced for the harm it can cause as well as its complete lack of scientific basis. Ingesting bleach can lead to severe fever, diarrhea, vomiting, and other complications.
Transcranial Magnetic Stimulation: TMS is a procedure in which magnetic fields are used to stimulate nerve cells in the brain to enhance or reduce certain functions. TMS is currently used to treat mental illnesses, including depression and schizophrenia. The most commonly reported short-term side effects include headaches and scalp discomfort. Therapeutic TMS is relatively new so long-term side effects, if any, are unknown. Investigations into the efficacy of TMS in ASD treatment are currently underway, but presently there is no evidence to support its use.
Psychological and Behavioral Non-Evidence-Based Treatments
Therapeutic Horseback Riding: Horseback-riding therapy for individuals with ASD aims to foster motor, communication, and social skills, while improving responses to external stimuli. Although a few studies touting the benefits of therapeutic riding have been published in peer-reviewed journals, they are either mainly descriptive, involve small samples or rely on poor outcome measures, and thus cannot support the therapy as a useful, evidence-based intervention.
Dolphin-Assisted Therapy: When undergoing dolphin-assisted therapy (DAT), an individual with autism swims, touches, and interacts with dolphins. Alleged benefits of dolphin therapy include improved emotional control and communication skills, as well as increased attention. Some proponents also claim that the emotional experience created by DAT helps individuals become more receptive to more conventional treatments. There is no scientific evidence suggesting that DAT is efficacious in the long-term improvement of ASD symptoms. Moreover, DAT involves significant safety risks given that dolphins are powerful animals that are capable of harming humans despite extensive training.
Prism Glasses: Prism glasses alter the visual perception of individuals with ASD and are thought to improve behavior and challenging vision-related symptoms as a result. Supporters believe that some individuals with ASD suffer from distorted perception and compensate using abnormal movements and postures such as head tilting. Prism glasses aim to ameliorate perceptual distortions and aid visual development. Their purported benefits extend to other areas, including spatial localization, visual awareness, decrease in sensory seeking behaviors, organization, gait, eye contact, mood, facial expressions, and fine and gross motor skills. Unfortunately these benefits have no scientific backing; no studies with strong experimental designs have supported the use of this expensive therapy in individuals with autism.
Music Therapy: Music therapy aims to mitigate cognitive, behavioral, social, and sensory-motor impairments in individuals with ASD. Although music therapy may be rewarding for individuals with ASD, there is no strong scientific evidence for its efficacy in improving functioning.
Holding Therapy: Holding therapy is based on the erroneous notion that autism is a disorder of attachment caused by a parent’s failure to bond with their child. In a holding therapy session, a caregiver physically restrains a child with autism in order to force eye contact and repair attachment. This treatment has been deemed ineffective and dangerous. There is no scientific evidence suggesting that holding therapy works and fatalities have resulted from its use.