Tylenol and Autism: Beyond Vaccines
Evidence, Scientific Blunders, and Medicine Gone Wrong
New book from Children’s Health Defense by William Parker, PhD
When I was a medical student on the adolescent ward at Children’s Hospital of Pittsburgh in 1980, I had a teenage patient with Reye’s syndrome who was in a coma for after taking many doses of aspirin for a viral illness. He was admitted with liver dysfunction and cerebral edema, the 2 classic signs of the disease which had a 31% fatality rate. An intracranial pressure monitor was placed by the neurosurgeons, and fortunately, with supportive care from the pediatricians, he made a complete recovery.
In 1982, the US Surgeon General issued an advisory recommending avoiding salicylates in treating viral illnesses, and in 1986, the FDA mandated that aspirin labels state that children should not use the product. As a result, Tylenol (acetaminophen) became the recommended drug for fevers in childhood during this time period. 1985 marked the beginning of the surge in autism diagnosis from 5 per 10,000 prior to that year to 67 per 10,000 by 2004, but no link was made to Tylenol.
In 2008, the first scientific paper to suggest that acetaminophen (paracetamol) might be the cause of autism was published by Schultz in the journal Autism. It was a case-control study of 83 children with autistic disorder and 80 control children showing acetaminophen use after measles-mumps-rubella (MMR) vaccination was significantly associated with autistic disorder when considering children 5 years of age or less. Ibuprofen use after MMR was not associated with autistic disorder.
The story now shifts to William Parker, PhD, the author of Tylenol and Autism: Evidence, Scientific Blunders, and Medicine Gone Wrong, just published on 6/23/2026. I met him for the first time that day at a book launch party I was invited to by Laura Bono, local Durham mother of an autistic son, who was one of the co-founders of Children’s Health Defense along with Robert F. Kennedy, Jr. It turned out William was also a former Duke Associate Professor, and we discovered we had a lot in common.
As a researcher in the Department of Surgery, he collaborated with surgeon and immunologist Randy Bollinger, who wrote the foreword to his book. Their initial claims to fame were discovering bacterial biofilms in the healthy human gut in 2004 and that the human appendix was a safe house for beneficial bacteria serving as protective reservoir against severe diarrheal disease in 2007. That reputation led to Laura Bono contacting him about studying gut dysfunction in children with autism.
In 2013, independent researcher William Shaw published a paper pointing out that the autism rate in the US is 298 times higher than in Cuba where there is a compulsory vaccination rate of 99%, but the use of acetaminophen for fevers is rare. This paper is available in the Journal of Restorative Medicine but is now preceded by a statement from the publisher noting that the use of Tylenol in pregnancy decreased between 2004 and 2018 while the rate of autism has continued to increase.
In a 2017 paper, Parker and his colleagues explored the association of oxidative stress and inflammation with autism and evaluated possible environmental factors. Aspartame which is broken down into toxic methanol and mercury-containing vaccines were considered, but the incidence of autism continued to rise after their curtailment. Acetaminophen, which has never been shown to be safe for neurodevelopment, emerged as a likely suspect for the cause of autism.
In his book, Parker notes that there is extensive evidence for immune dysregulation from repeated childhood vaccinations leading to the epidemic of chronic illness including many autoimmune conditions such as asthma and eczema. In fact, there are 18 studies showing that vaccinated children are much sicker than unvaccinated children with none showing the opposite. After thimerosal was removed from most vaccines, there was an increase in other immunogenic adjuvants like aluminum.
These studies also showed a marked increase in autism and ADHD, but Parker proposes that these neurodevelopmental disorders are caused primarily by the large doses of Tylenol given routinely with the vaccines. Anxiety about fevers induced by the vaccines often results in acetaminophen being given every 4 hours for several days even though there is evidence this protocol will not prevent febrile seizures. Although these seizures may be scary for parents, there is no evidence of long-term effects.
Unfortunately, as Parker points out in his 2023 paper, this approach creates a vicious cycle of oxidative stress leading to brain damage. He cites 30 independent lines of evidence for autism being caused by Tylenol exposure during a vulnerable period of childhood before the age of 6 when children have limited capability of metabolizing acetaminophen. On average, babies gain these abilities by age 2, but autistic children may be more deficient in these sulfation and glucuronidation detoxification pathways.
Young children are similar to cats which also are deficient in a glucuronyl transferase enzyme that can result in death due to acetaminophen toxicity. In fact, there are many animal studies showing harm to developing neurons in young rats and mice. A toxic metabolite, N-acetyl-p-benzoquinone imine (NAPQ1), has been identified as causing mitochondrial damage and neuroinflammation. Even in adults, there is evidence that Tylenol causes decreased neighborhood trust and social integration.
Tylenol use in pregnancy is controversial, made more so by President Trump’s advice in a September 2025 White House briefing, "Don't take Tylenol if you're pregnant, and don't give Tylenol to your child." The evidence for harm from occasional use during pregnancy is weak, but risk goes up dramatically during delivery as umbilical cord levels of acetaminophen correlate with later autism diagnosis. After birth, the President is correct as Tylenol is soon given with unnecessary Hepatitis B vaccines.
Dr. Parker concludes the book with the following 5 recommendations for regulatory agencies and physician associations which are copied verbatim below.
1: Administration of acetaminophen in a manner that was never intended should be discontinued. This includes treatment of temperatures that do not technically constitute a fever and administration of the drug more frequently and at higher doses than recommended.
2: Administration of acetaminophen under conditions in which evidence demonstrates a lack of effectiveness should be discontinued. This includes the treatment of the pain of circumcision and perhaps the treatment of fevers to prevent febrile seizures.
3: Administration of acetaminophen under conditions in which no evidence demonstrates long-term benefits of treatment or in which evidence demonstrates a lack of long-term benefits should be discontinued. This includes the treatment of fevers and prophylactic treatments prior to labor and delivery.
4: Administration of acetaminophen that is no longer recommended by governing medical bodies should be discontinued. This includes the treatment of patients receiving vaccinations and will hopefully include many more reasons for administration in the future.
5: Administration of acetaminophen under conditions where evidence indicates that it is or may be beneficial should not be continued without disclosure of the drug’s long-term risks for neurodevelopment. All caregivers, including parents, should be made aware of evidence related to both benefits and risks so that they can make informed decisions.
In terms of practical advice for parents, it is necessary to go full circle back to Reye’s syndrome, as there has been debate since 2002 about whether aspirin was the cause or whether it was actually a metabolic disorder related to a viral mutation. The first cases were described in 1951 and the last cases disappeared in the late 1980s attributed to termination of aspirin treatment. However, it also vanished from countries where aspirin was not even used. Dr. Reye himself concluded that aspirin was not the cause.
Regardless of whether aspirin was the causative agent, it is important to know that the age range for Reye’s syndrome is between 5 and 14 years, and it is rare under age 1. Since the most vulnerable period for neurotoxicity from Tylenol is under 1 year, it might be worth considering bringing back Baby Aspirin for infants. Ask your doctor for advice and if possible, treat a fever without medication by avoiding overheating, preventing dehydration, discouraging overexertion, and giving lukewarm baths.