Does drinking diluted chlorine dioxide protect against COVID-19?

Question

I read a bit about drinking diluted chlorine dioxide (e.g. 12mg/L) as a supposedly protective means against COVID-19. Apparently it is a widespread belief in Latin America, especially on social media, that this is a good alternative to getting vaccinated. Here is an article that explores how the usage of ClO₂ against COVID-19 became such a widespread practice throughout Latin America: https://osf.io/u9ehf/download.

People who follow this practice support their assertion of efficiency against COVID-19 with articles like the following:

• Efficacy and Safety Evaluation of a Chlorine Dioxide Solution (2017)

• Protective effect of low-concentration chlorine dioxide gas against influenza A virus infection

• Evaluation of the Antiviral Activity of Chlorine Dioxide and Sodium Hypochlorite against Feline Calicivirus, Human Influenza Virus, Measles Virus, Canine Distemper Virus, Human Herpesvirus, Human Adenovirus, Canine Adenovirus and Canine Parvovirus (2010)

• Effect of chlorine dioxide gas of extremely low concentration on absenteeism of schoolchildren (2009)

• Chlorine dioxide inactivation of enterovirus 71 in water and its impact on genomic targets

• Activated chlorine dioxide solution can be used as a biocompatible antiseptic wound irrigant

Answer 1

DO NOT DRINK BLEACH!

Chlorine dioxide is a type of bleach.

The Blue Ridge Poisoning Center at University of Virginia Health put out a specific warning not to drink bleach.

There is a lot of confusing, incomplete, and just plain inaccurate information circulating about how to prevent the COVID-19 virus (“coronavirus”) from spreading. Some advice measures simply won’t help, and some could be downright dangerous. The Blue Ridge Poison Center at UVA Health warns that drinking bleach will not prevent COVID-19 infections and could cause serious injury.

When used correctly, cleaning products can be a safe and effective weapon against the spread of disease-causing germs including the COVID-19 virus (“coronavirus”). In particular, the U.S. Centers for Disease Control and Prevention (CDC) recommends using diluted bleach solutions on frequently-touched surfaces. Hand sanitizer with an alcohol content of at least 60% is recommended for killing COVID-19 on the hands, especially when soap and water is unavailable. However, these products and others used to clean and disinfect may have the potential to be toxic if used incorrectly. Exposure to cleaning products is the second leading cause of calls to poison centers nationwide.

Some cleaning products (including bleach) are caustic, meaning they can cause burns when swallowed or when sprayed or splashed onto the skin or into the eyes.

After Trump suggested injecting disinfectants (dear lord), the CDC had to remind everyone not to do that.

Household cleaners and disinfectants can cause health problems when not used properly. Follow the instructions on the product label to ensure safe and effective use.

In a similar tale, the FDA warned against using the Miracle Mineral Solution which is basically bleach.

Miracle Mineral Solution and similar products are not FDA-approved, and ingesting these products is the same as drinking bleach.

12 mg/L may be hazardous to your health

Very low concentrations can have benefits. It's used as a secondary disinfectant in drinking water. The US EPA puts the maximum safe level in drinking water at 0.8 mg/L.

12 mg/L is well above that and inadvisable.

There is no way to demonstrate it's working, until it doesn't

Outside of a controlled experiment, this treatment will seem to prevent COVID-19 right up to the moment it does not. Meanwhile, it's damaging the body with a caustic substance.

Quackery such as this is not harmless. The health care system does not need another sick person (from long-term chemical poisoning) on their hands. If one truly believes they are immune to COVID they are more likely to put themselves at risk of getting and spreading COVID, especially because may be contagious before they have severe symptoms.

Bleach kills everything, including humans

The papers fall into two categories.

• bleach against various viruses (not COVID-19) in a lab
• bleach against various viruses (again, not COVID-19) on humans at safe levels

I'm going to guess folks cherry-picked "bleach is effective against viruses" and "bleach can be used on humans" ignoring the "in a lab" and "at safe levels".

Bleach is very good at killing viruses. This does not mean it only kills viruses. Bleach kills everything, that's why it's so good at disinfecting surfaces. Everything includes humans. We use bleach on humans in very low concentrations because we would like to keep the human alive. Fire is also a pretty good disinfectant, but it is also very harmful to humans. Don't drink fire either.

None of the papers are about drinking unsafe amounts of bleach to cure COVID

None of these papers are about COVID-19. None are about drinking unsafe amounts of bleach. Their only relation is they are about uses of chlorine dioxide, mostly against viruses.

• Efficacy and Safety Evaluation of a Chlorine Dioxide Solution is about a new method to reduce the impurities in bleach to make it less toxic (not safe).
• Protective effect of low-concentration chlorine dioxide gas against influenza A virus infection was done on mice against the flu using a gas at at safe levels.
• Evaluation of the Antiviral Activity of Chlorine Dioxide and Sodium Hypochlorite against Feline Calicivirus, Human Influenza Virus, Measles Virus, Canine Distemper Virus, Human Herpesvirus, Human Adenovirus, Canine Adenovirus and Canine Parvovirus is comparing the efficiency of two different disinfectants at various concentrations against various viruses in liquid solution, not by drinking it.
• Effect of chlorine dioxide gas of extremely low concentration on absenteeism of schoolchildren (2009) This used bleach as a gas at safe levels on students.
• Chlorine dioxide inactivation of enterovirus 71 in water and its impact on genomic targets is about the effect of bleach on the genome of hoof-and-mouth disease in a lab.
• Activated chlorine dioxide solution can be used as a biocompatible antiseptic wound irrigant. This is about using bleach to clean wounds, not drink it. We use plenty of substances to clean wounds which are toxic if ingested.

Not a single one is about drinking bleach at 12 mg/L for any reason.

I don't care how bored you are, do not drink bleach.

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Before you comment, please keep in mind this is an answer about drinking unsafe amounts of bleach to prevent COVID. It is not a dissertation on the medicinal uses of chlorine dioxide. As such, it is not intended to be technically correct, it is intended to be blunt. Don't drink bleach. It will not prevent COVID.

Nerdy anecdotes such as this one and touch up edits are always welcome.

Answer 2

It may be worth adding that the WHO sets a somewhat higher threshold for toxicity than the EPA, for chlorine dioxide in water, namely 2mg/L.

Anyhow, the problem is that there don't seem to be even animal studies finding that at non-toxic levels (for the host) chlorine dioxide helps with an already established viral infection. So basically there's zero evidence, even from animal studies that it could be a treatment.

Edit: Actually, this is not entirely correct, Peter's answer points to a [not yet formally peer-reviewed/published] preprint of a study in chicken embryos, but it's a bit disconcerting that such a study was only done recently [2020], when chlorine dioxide has been used as a disinfectant for decades. So, you could at least say that for internal use, this is a very experimental treatment, in preclinical stage at best. Also that study noted that "developmental abnormalities were observed in the majority of the infected embryos, including those that received ClO2 treatment", so it seems it's not that foolproof of a treatment, although treatment lowered the servility of some symptoms, including mortality. Viral load was only lowered 2.4-fold in the treatment groups (30-300 ppm ClO2) compared to controls; in absolute terms "average viral load of ClO2-treated chicks was 10^4.3/mL, range: 10^3.66 – 10^5.03 and of untreated chicks was 10^4.83/mL, range: 10^4.52 – 10^5.01, respectively (Tukey HSD, Group E vs. F, p = 0.03)." The study was also limited to a single dose of ClO2, which limited both toxicity [to the host] and effectiveness against the virus. Before any human trials, more complex animal models would have to be tested. E.g. look at how oseltamivir was tested in various animal models; an antiviral like that completely inhibited virus replication in some organs but only partially in other organs in the same animal etc. Chicken embryos are really on the lowest step of the ladder of in vivo (animal) models.

On the interesting, but not-really-relevant side, besides the plethora of studies on chlorine dioxide as an additive in water treatment (remember again, the dose makes the poison) which mostly what the OP linked to, there is also one study on chlorine dioxide killing influenza viruses aerosols. (Again this was at host-safe levels.)

Mice in semi-closed cages were exposed to aerosols of influenza A virus (1 LD50) and ClO₂ gas (0.03 p.p.m.) simultaneously for 15 min. Three days after exposure, pulmonary virus titre (TCID₅₀) was 10^2.6±1.5 in five mice treated with ClO2, whilst it was 10^6.7±0.2 in five mice that had not been treated (P=0.003). Cumulative mortality after 16 days was 0/10 mice treated with ClO₂ and 7/10 mice that had not been treated (P=0.002).

Actually, part of study that strongly indicates that the relevant effect happens outside the body: if application of the ClO₂ gas is delayed relative to the virus aerosol, the mice still die aplenty:

When ClO₂ gas was delivered 5 min after the delivery of virus aerosols (5 min delay), mortality was 10 % (1/10) (P=0.081 versus no-ClO₂ group). The mortality rate was 50 % (5/10) with a 15 min delay, which was [statistically] the same as in animals that received no ClO₂ gas treatment.

Thus the ClO₂ gas doesn't really treat already infected mice. (It's a bit more complicated why the window is 15 mins, basically the virus has to make its way through mucus etc.)

So, this in aerosol form it could be potentially be a more useful application against a mainly airborne pathogen, but there are substantial practical difficulties putting it in widespread practice since you really need to kill/inactivate the virus before it enters the body with this method/substance.

Additinally, the WHO and the health ministry of Japan have said in a statement that fumigation/spraying devices that are loosely based on that idea (e.g. blow a mist/aerosol of chlorine dioxide in people's faces) aren't approved or effective and that some adverse events have been reported in Japan after exposure to such devices. (There's no technical detail in that newspaper report why the authorities cited say that, but it's probably related to the difficulty of ensuring the (effective but non-toxic) concentration in a larger volume of air from a point source etc.)

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Since I see there's some discussion under the other answer about disinfectant mouthwashes... Various kinds of these have been studied with respect to reducing the amount of virus emitted by Covid-19 patients, particularly in a dentistry setting. (There is actually mouhtwash based on chlorine dioxide, although it's not commonly used in dentistry.) But the effect of any such mouthwash products is quite transient, on the order of a few of hours as measured by salivary viral loads (which don't quite drop to zero). Also there has been substantial heterogeneity in the results reported, even for the same active substance; some studies found no reduction, others found a load reduction e.g. in half the patients tested, but not in all of them some reason (which is not really understood). So even for this limited purpose of acting like a "chemical mask" reducing the amount of virus emitted, the evidence regarding disinfectant mouthwashes is mixed.

Answer 3

Summary: There is no evidence that ingesting Chlorine Dioxide cures or protects from COVID-19, but the idea is not a priori as patently absurd as it may seem at first glance.

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Molecular Chlorine and some chlorine compounds like sodium hypochlorite or chlorine dioxide are known to be effective disinfectants outside of the body. Chlorine dioxide, a water soluble gas, is used in low concentration to treat drinking water. According to the Agency for Toxic Substances and Disease Registry millions of people ingest it every day for this reason.

Inhaling Chlorine dioxide as a gas above safety limits has adverse health effects:

Breathing Chlorine Dioxide can irritate the lungs causing coughing and/or shortness of breath. Higher exposures can cause [...] pulmonary edema

- Chlorine Dioxide Hazrdous Substance Fact Sheet.

This establishes the known frame conditions:

• Dissolved Chlorine dioxide is effective in deactivating SARs-COV-2 outside of the body.
• It can be drunk safely in very low concentrations.
• It has adverse health effects in higher concentrations, particularly when inhaled.

Is it dangerous?

Severe adverse health effects from low concentrations are not to be expected. In other words: Yes, go ahead and drink chlorine dioxide solutions in dilutions below published safety limits if you feel like it. Millions of people do it every day.

However, the reported 12mg/L concentration is an order of magnitude more concentrated than what is considered safe for drinking water by the EPA. Several studies have shown no adverse affects in animals and cell cultures even well above that concentration (e.g. https://res.mdpi.com/d_attachment/ijerph/ijerph-14-00329/article_deploy/ijerph-14-00329.pdf), but there have been reports of life-threatening adverse events, including respiratory and liver failure, at even higher concentrations.

Does it prevent or cure COVID-19?

A possible therapeutic use of chlorine dioxide in low concentrations would not contradict the above facts, but there is no medical evidence that it does.

I could not find a randomized controlled study which showed whether or not it can prevent or cure Covid-19 when ingested. (Obviously though there was not a lot of time to perform one.)

There is a lot of crackpot activity in this field, ranging from irresponsible charlatans to researchers with an agenda¹. None of them are robust clinical studies.

But the idea is not a priori as patently absurd as one may think at first glance.

For example, there is a study showing that ClO₂ "inhibits the replication of porcine reproductive and respiratory syndrome virus" in cell cultures. Of course, I cannot assess the quality of this study, it does not address SARS-CoV-2, it is ex vivo and it does not seem to be widely cited.

There are a few other, non-peer-reviewed studies performing in vitro or animal experiments.

For example, Evaluation of the antiviral effect of chlorine dioxide (ClO2) using a vertebrate model inoculated with avian coronavirus which showed show that it lowered the viral load of avian coronavirus (IBV, not SARS-CoV2) in tissues of chick embryos.

Our study shows that ClO2 could be a safe and viable way of treating and mitigating the effects of avian coronavirus infections, and raises the possibility that similar effects could be observed in other organisms.

Interestingly, there is a study on mice (https://pubmed.ncbi.nlm.nih.gov/18089729/) that shows how very low-concentrated chlorine dioxide gas in the air mitigates or prevents over-the-air infections with the Influenza A virus. Since the influenza virus has a lipid hull like SARS-CoV-2, low amounts of chlorine dioxide in the air might similarly prevent infection with SARS-CoV-2.

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¹ E.g. https://www.hilarispublisher.com/open-access/chlorine-dioxide-in-covid19-mechanism-of-molecular-action-in-sarscov2.pdf, whose authors are from the Liechtensteiner Verein für Wissenschaft und Gesundheit which promotes "principles of natural holistic medicine". Never mind holistic approaches to health; they are dearly needed. But unfortunately that label often means "substitute evidence with conviction".

Answer 4

Is there any evidence it works?

I have not done extensive reading on this topic, but based on the sources you linked, no, there is no evidence ingesting ClO₂ is either preventative or a treatment once infected.

There is very limited evidence that an aerosol of ClO₂ may have some protective effect, but the evidence seems to suggest this effect comes from killing the virus in the air before it reaches the victim. The evidence does not support any beneficial effect from a ClO₂ aerosol once one is infected.

This paper (from a very crappy journal) gives an overview of some of the evidence. As the authors themselves state:

"Many of these propositions are based on hypotheses, and therefore can only be applied after careful research".

I will also note that the authors are focused on using a ClO₂ aerosol as preventative treatment (tenuous but possible) and not ingesting a ClO₂ solution.

Is it reasonable to speculate this might work?

While everyone has a different definition of 'reasonable', I would say no, this does not sound feasible.

In order for a disinfectant of this nature to have any effect, it needs to physically reach the virus at a sufficient concentration in order to 'kill' it. The only way for a disinfectant of this nature to reach the virus in an infected individual would be for it to survive their digestive system, enter the bloodstream, and evade filtration by their liver and kidneys. Assuming this is all possible, it then needs to be at a high enough concentration in the blood to kill the virus upon contact. My guess is that at this concentration ClO₂ would also start causing lots of other problems including, but not limited to, killing off your own cells.

I am not a doctor or a toxicologist, so this assumption could be incorrect. Without any clinical or experimental data to back up the safety of systemically circulating ClO₂ in blood though I think it is best to err on the side of caution.

What this does mean, however, is you would likely need to ingest fairly large quantities of ClO₂ in order to achieve the necessary concentration in your blood. (ie 2mg/L ingested <<< 2mg/L in blood, avg. person has ~5L blood) This is likely to exceed current safety limits.

How might I explain this to my friend?

If your friend has a hard time understanding why this isn't feasible you could point to alcohol. Ethanol (the alcohol in beer, wine, and spirits) can kill coronaviruses at a 70% ethanol-to-water concentration (for reference, most spirits such as bourbon and vodka are around 45% ethanol). Despite this, no one is suggesting you drink large quantities of alcohol in order to prevent viral infection. This is because 1) drinking enough to get your blood alcohol concentration even near 55% (the lower bound for efficacy of ethanol as a viral disinfectant) would definitely kill you and 2) heavy alcohol consumption on a regular basis actually suppresses your immune system (for complicated reasons)

While this analogy is far from perfect, it still might be useful in trying to convince the average person why just because something can kill covid in a dish does not mean that ingesting it will be protective or preventative.

So, while ClO₂ may kill covid in your drinking water, there is no evidence or reason to believe that drinking such a solution would kill covid in your body, any such claims are purely speculative.