Hydrogen peroxide (H₂O₂) is a common household chemical used for cleaning and as an antiseptic. This colorless liquid is a powerful oxidizer. Its role in combating pathogens like SARS-CoV-2 (COVID-19) is a frequent question for many people. It is important to understand how this compound works, its limitations for surface disinfection, and the significant dangers of using it incorrectly.
Effectiveness Against the Virus on Surfaces
Hydrogen peroxide is an effective agent for inactivating SARS-CoV-2 when used as a surface disinfectant. The virus is known as an enveloped virus, meaning it has an outer fatty layer that is easily disrupted by disinfectants. The concentration required for effective cleaning is a primary factor in its success.
Standard household hydrogen peroxide is typically sold at a 3% concentration, which is potent enough to kill the virus. Many commercial disinfectants, including those with accelerated formulations, use lower concentrations (sometimes 0.5% or less) because of synergistic ingredients that boost efficacy. The U.S. Environmental Protection Agency (EPA) maintains a list of approved disinfectants that meet the criteria for use against SARS-CoV-2.
The necessary contact time, also known as dwell time, is another factor for successful disinfection. For household 3% hydrogen peroxide, a minimum contact time of 10 minutes is often recommended to ensure the virus is inactivated on hard, non-porous surfaces. Commercial formulations often achieve a shorter dwell time, sometimes as low as one minute, due to their specific stabilizers and concentration. Always follow the instructions for the specific product label.
How Hydrogen Peroxide Kills Pathogens
Hydrogen peroxide functions as a broad-spectrum germicide by a process called oxidation. The compound is naturally unstable and readily decomposes, particularly in the presence of organic material or light. This decomposition results in the production of highly reactive oxygen species, such as hydroxyl free radicals.
These free radicals are damaging to biological molecules because they aggressively steal electrons from other compounds. This process causes oxidative damage to the essential structures of the virus, including lipid membranes, proteins, and nucleic acids. The destruction of the viral envelope and the modification of proteins, such as the spike protein, renders the virus incapable of infecting host cells. Hydrogen peroxide is highly effective at structurally destroying the virus rather than simply inhibiting its growth.
Dangers of Personal or Internal Application
Despite its effectiveness as a surface disinfectant, hydrogen peroxide is not approved for internal use to treat or prevent COVID-19. Dangerous misinformation has suggested practices like ingestion, gargling, or inhaling the substance via a nebulizer. Using hydrogen peroxide internally, even in diluted form, can cause significant harm to human tissue.
Ingesting hydrogen peroxide can lead to severe gastrointestinal damage, causing chemical burns to the esophagus and stomach lining. High concentrations can also cause a condition called gas embolism, where oxygen gas bubbles enter the bloodstream and block arteries.
Inhaling the substance, particularly through a nebulizer, is hazardous, as it directly damages the delicate tissue of the lungs and respiratory tract. The oxidative stress that makes it a disinfectant is indiscriminate, meaning it damages human cells just as easily as viral particles.
The practice of nebulizing hydrogen peroxide can cause severe inflammation, irritation, and chemical pneumonitis, potentially worsening symptoms in people already experiencing respiratory distress from COVID-19. No recognized medical or public health authority recommends using hydrogen peroxide inside the body to combat the virus. Applying high concentrations to mucous membranes can also cause localized irritation and tissue damage.
Comparing Hydrogen Peroxide to Other Disinfectants
Hydrogen peroxide occupies a unique position among common disinfectants like alcohol and bleach because of its chemical breakdown. A primary advantage is that it degrades into only water and oxygen upon use, leaving behind no toxic residue. This makes it a preferred option in environments where chemical residue is a concern, such as food preparation areas.
However, hydrogen peroxide has practical disadvantages when compared to alternatives. The solution is less stable than bleach and has a shorter shelf life once the bottle is opened, as it continuously decomposes. It can also cause discoloration or bleaching on fabrics and certain materials, similar to chlorine bleach.
In terms of speed, alcohol solutions containing at least 70% ethanol or isopropyl alcohol inactivate viruses faster than hydrogen peroxide, sometimes in seconds. Alcohol can damage porous surfaces like wood, while hydrogen peroxide is often safer for a wider variety of household materials. Bleach, while inexpensive and fast-acting, is highly corrosive to metals and produces irritating fumes, which hydrogen peroxide does not.