Thimerosal, containing ethylmercury, is the active agent in Beech Tree Labs’ anti-viral formulation, BTL-tml. This therapy has demonstrated efficacy in alleviating symptoms of viral disease caused by Covid-19, influenza, herpesvirus, and Ebola. Contrary to unsubstantiated claims of harm caused by thimerosal, this agent has an extensive safety profile, especially when considering the nanogram dosage in the BTL-tml formulation.


Thimerosal is an organic compound used since the 1930s as a preservative in eye drops, cosmetics, and vaccines to prevent possible life-threatening effects of contamination.¹ Its use in vaccines has been cited as a possible link with autism. However, numerous scientific studies have found no causal association between thimerosal and autism, including effects during prenatal and early childhood exposure.²⁻⁵ Citing that the level of thimerosal in vaccines is not harmful, The Children’s Hospital of Philadelphia notes the difference between ethyl- and methylmercury and that the latter, which may be confused with ethylmercury, is found in the food chain such as with fish and can be toxic to humans at high levels of exposure.⁶ 


Historically, there have been studies where the effects of methylmercury are thought to be the same as ethylmercury, and therefore the two are equated. But it is now known that these forms of mercury have different metabolism and toxicity profiles. Unlike methylmercury, for example, ethylmercury does not accumulate in the body as it is eliminated through normal bowel movement.6 Other studies show that ethylmercury does not accumulate in the blood, is rapidly metabolized, and levels after exposure return to normal within a few weeks.⁷, ⁸ 


Consistent with other scientific information, BTL-tml has demonstrated efficacy and safety in two FDA-authorized clinical trials targeting herpesvirus infection. Combined results of these trials revealed clinically and statistically significant differences between BTL-tml treated patients and those receiving placebo. Attesting to safety, subjects in the placebo groups were three times more likely to report adverse events than subjects in the treatment groups.⁹ 


As part of the BTL-tml safety profile, it is administered sublingually and therefore not introduced into deep tissue as with vaccinations. Mechanism of action studies indicate that BTL-tml inhibits viral replication, downregulates several pro-inflammatory cytokine genes, and upregulates anti-inflammatory genes.¹⁰ 


The following graph and chart offer comparisons for exposure of methyl- and ethylmercury. Also presented are comparisons of animal studies focusing on thimerosal. Both provide evidence of BTL-tml’s safety.

    Based on a person weighing 68kg (150 pounds), a 7μg cumulative seven-day exposure to BTL-tml:
  • approximates the EPA recommended daily exposure limit over the course of a lifetime for the more toxic methylmercury (.1μg/kg/day).¹¹
  • is almost 20 times less than the WHO recommended daily limit of methylmercury exposure from all sources (2μg/kg/day).¹²
  • is almost four times less than the thimerosal (ethylmercury) contained in one pediatric vaccine dose
    (25μg/0.5mL).13, 14
The above chart represents a considerable amount of toxicology research pertaining to thimerosal. These studies involve different animal species, dosage, the route of administration, and teratogenicity (relating to birth defects). BTL-tml is consistently well within safety parameters.¹⁵, ¹⁶


  1. U.S. Food and Drug Administration. “Thimerosal and Vaccines.”, accessed May 25, 2022.
  2. Campbell A. “Thimerosal,” in Encyclopedia of Toxicology, third edition. New York: Elsevier Science & Technology, 2014.
  3. Price CS, et al. “CDC Study (2010) on Thimerosal and Risk of Autism.” Centers for Disease Control and Prevention., accessed May 25, 2022.
  4. Thompson WW, et al. “Early Thimerosal Exposure and Neuropsychological Outcomes at 7 to 10 years.” The New England Journal of Medicine, 357(13), September 27, 2007, 1281-1292.
  5. Hurley AM, et al. “Thimerosal-Containing Vaccines and Autism: A Review of Recent Epidemiologic Studies.” Journal of Pediatric Pharmacology and Therapeutics, 15, 2010, 173-181.
  6. The Children’s Hospital of Philadelphia. “Vaccine Ingredients – Thimerosal.”, accessed May 25, 2022.
  7. World Health Organization. “Mercury and Health.”, March 31, 2017, accessed May 25, 2022.
  8. Barregard L, et al. “Toxicokinetics of Mercury after Long-Term Repeated Exposure to Thimerosal-Containing Vaccine.” Toxicological Sciences, 120(2), 2011, 499-506.
  9. Mamber SW, et al. “Low-dose Oral Thimerosal for the Treatment of Oral Herpes: Clinical Trial Results and Improved Outcome After Post-hoc Analysis,” Journal of Evidence-Based Integrative Medicine, 27, 2022, 1-10.
  10. Mamber SW, et al. “Can Unconventional Immunomodulatory Agents Help Alleviate COVID-19 Symptoms and Severity?” mSphere, 5(3): e00288-20, May/June 2020, 1-6.
  11. U.S. Environmental Protection Agency. “What EPA is Doing to Reduce Mercury Pollution, and Exposures to Mercury.”, accessed May 25, 2022.
  12. World Health Organization. “Exposure to Mercury: A Major Public Health Concern, second edition.” Geneva, April 8, 2021.
  13. U.S. Food and Drug Administration. “Thimerosal Content of Available FDA-Approved Seasonal Influenza Vaccines.”, accessed May 25, 2022.
  14. Beech Tree Labs, Inc. BTL-tml Covid-19 Investigational New Drug Application, submitted August 20, 2020.
  15. Blair AMJN, et al. “Tissue concentrations of mercury after chronic dosing of squirrel monkeys with thiomersal.” Toxicology, 3, 1975, 171-176.
  16. Clarkson TW and Magos L. “The toxicology of mercury and its chemical compounds.” Critical Reviews in Toxicology, October 10, 2008, 609-662.