A prominent Austrian anti-vaccination advocate who said he attempted to treat his COVID-19 infection with a substance found in some bleach products has died after suffering complications from the disease.

Johann Biacsics, one of the leaders of the anti-vaccination movement in the country, reportedly contracted COVID-19 in October and said he began administering himself with a product containing chlorine dioxide, a substance that is touted by some as a treatment for the disease as well as many other ailments

In the United States, the Food and Drug Administration (FDA) has previously warned consumers not to purchase or drink chlorine dioxide products sold online as medical treatments because the agency is not aware of any credible scientific evidence supporting their safety or effectiveness.

In addition, these products pose a significant risk to the health of people who consume them, according to the agency.

A post on Biacsics' personal website made the claim that taking the chlorine dioxide (CDL) product successfully treated his infection.

"I took CDL and also made high-dose CDL enemas," the post said. "As it turned out later, I successfully fought COVID 19 with it. The self-tests I had done were all negative."

But the 65-year-old's condition worsened significantly and he was admitted to hospital in early November after experiencing low oxygen levels and difficulty breathing. Medical staff at the hospital administered a PCR test, which came up positive, German weekly Die Zeit reported.

Biacsics refused the treatment plan that doctors offered him, convinced that he had beaten the acute infection. Eventually, he decided to leave the hospital, calling his son who picked him up and took him home.

Biacsics ordered everything he needed to administer chlorine dioxide infusions to himself. But just two days later, he passed away. It is not clear whether Biacsics' consumption of CDL contributed to his death.

Biacsics had previously made false claims that chlorine dioxide could be used to treat COVID-19 infections.

According to the FDA, consuming products that contain chlorine dioxide can potentially be "life-threatening."

Consumption of these products can lead to serious adverse events including respiratory failure, changes in the electrical activity of the heart, life-threatening low blood pressure caused by dehydration, acute liver failure, low blood cell counts, severe vomiting and severe diarrhea.

Chlorine is commonly used to disinfect drinking water and it is safe for this purpose when used in very small amounts. When used in large quantities, however, it can be dangerous.

Stock image showing a chlorine dioxide product. Austrian anti-vaxxer Johann Biacsics, who said he treated his COVID-19 infection with chlorine dioxide, has died.iStock