Usnic Acid Inhibits Viral Respiratory Infection

Reproduced from original article:

Analysis by Dr. Joseph Mercola      Fact Checked      February 09, 2021

usnic helps inhibit flu virus


  • Usnic acid is a metabolite of lichens and was first isolated in 1844; derivatives have demonstrated activity against influenza virus strains and a derivative modified with valine reduced deaths in infected animals without liver toxicity
  • Usnic acid has not prompted the development of resistant influenza as Tamiflu and other antiviral medications have done. Tamiflu reduces symptoms of flu by less than one day
  • Flu vaccines have not been effective as scientists must predict what strains will be most virulent the coming season and people who are routinely vaccinated shed over six times more virus in the air
  • There are strategies you can use at home to help prevent flu and treat upper respiratory infections if you get one, including optimizing vitamin D, nebulized hydrogen peroxide and taking zinc and quercetin

The influenza virus has a high rate of mutation and can develop drug resistance. Research has found derivatives of usnic acid can effectively inhibit the reproduction of the influenza virus in the lab and animal models.1

The influenza virus causes a contagious respiratory illness better known as flu.2 The virus infects your nose, throat and sometimes lungs triggering disease that can range from mild to severe. Symptoms include fever, cough, muscle or body aches, fatigue and sore throat. Children may experience vomiting and diarrhea with flu infection.

There are four types of influenza virus that are named by letters: A, B, C and D.3 Influenza D is not known to infect people but causes illness in cattle. Influenza A, B and C infect humans. Influenza A is the only type known to cause a pandemic. Influenza A and B can cause epidemics, and influenza C generally causes mild illness.

Influenza A and B cause most human flu illnesses, and each is classified and subclassified based on genetic sequencing.4 Each year experts attempt to match the flu vaccine by estimating the strains of virus expected in the U.S.5

The CDC estimates from 3% to 11% of the population will have symptomatic flu disease each season, although during the 2020-2021 flu season, infections have been almost nonexistent. Typically, however, up to 20% of the population can have asymptomatic or symptomatic illness.6 The estimated number of deaths from flu have ranged from 12,000 to 61,000 annually from 2010 to 2020, depending on the flu season.7

Since the influenza virus can affect millions of people each year, scientists have sought to develop an effective and safe antiviral treatment to reduce the burden of the illness. However, as I discuss below the results have not lived up to the promise.

Usnic Helps Inhibit Flu Virus Without Stimulating Resistance

Usnic acid was first isolated in 1844 and since then has been extensively studied as one of the few commercially available lichen metabolites.8 Lichen has been included in folk medicine from many countries.9 Early studies of lichen biological activity in New Zealand led to the identification of usnic acid “as the main antimicrobial, cytotoxic and antiviral component.”10

Subsequently, this led to a study of usnic acid and its derivatives against the H1N1 pandemic influenza virus.11 Isomers of usnic acid and the derivatives were tested and the results suggested derivatives should be considered for use against the influenza virus.

Usnic acid was also tested against the virulent influenza A virus and researchers found they could boost the activity by modifying the compound with chalcones.12 These are an important class of flavonoids that scientists have used to create derivatives and:13

“… improve pharmacological activity, gain selectivity for a particular receptor or enzyme with simultaneous reduction of certain adverse effects, or even for optimizing the pharmacokinetics of the lead candidate.”

Derivatives of usnic acid modified with chalcones demonstrated biological activity against the influenza virus in the lab and in an animal model.14 The researchers tested a broad range of viral strains and the results demonstrated activity against these strains.

Additionally, one compound modified with valine demonstrated the capacity to reduce the number of deaths in infected animals and did not trigger the development of a resistant strain of influenza. The researchers concluded that this modification increased the antiviral properties and lowered the potential for toxicity to liver tissue.15

Hepatotoxicity is an important consideration when using usnic acid. A patent review from 2000 to 2017 found applications for use were withdrawn secondary to liver toxicity.16 The results of animal studies have suggested the mechanism for injury is oxidative phosphorylation, increased oxidative stress and depletion of glutathione.17

Antimicrobial resistance is a significant challenge to modern medicine, and the influenza virus can also mutate to become resistant to antiviral drugs.18 As research has demonstrated, some usnic acid derivatives address several challenges of fighting flu, namely they are effective against influenza, do not prompt the development of resistant strains and have low hepatotoxicity.19

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What Is Usnic Acid?

Usnic acid is a secondary metabolite produced exclusively by a variety of lichen species,20 which researchers have discovered has antiviral, anti-inflammatory, antioxidant, antifungicidal and antineoplastic activity.21

Secondary metabolites are organic molecules an organism produces that are not crucial for their reproduction, growth or development, but give a selective advantage.22 For example, secondary metabolites may slow the growth of a competing organism and secondary metabolites from fungi have produced antibiotics such as penicillin.

Usnic acid has strong antibacterial properties and for this reason has been incorporated into toothpaste, mouthwash, deodorant and moisturizing creams.23 It is also used as a preservative in cosmetic products. The antibacterial properties include the ability to inhibit staphylococcus aureus biofilm formation on medical devices and potentially inhibit other gram-positive organisms as well.24

Usnic acid has been promoted for weight loss, but the supplements sold are associated with severe liver toxicity. Topical use can also cause an allergic reaction or local irritation.25 Research has demonstrated the compound has environmental effects including antiherbivore and anti-insect properties.26

Studies Cast Doubt on Value, Safety of Flu Drugs Like Tamiflu

Antiviral flu drugs like Tamiflu (oseltamivir) and Relenza (zanamivir) are conventional medicine’s go-to option for treating the flu, despite their risk of serious side effects and unproven benefits. In fact, these drugs were stockpiled in many countries, including the U.S.,27 for treating and preventing seasonal and pandemic influenza.

In 2010, the World Health Organization (WHO) even classified Tamiflu as an “essential” medicine.28 In 2014, Dr. Mark H. Ebell from the college of public health at the University of Georgia published an editorial in The BMJ29 calling the events surrounding Tamiflu a “multisystem failure,” based on decisions by the CDC, WHO and EMA that included the failure to publish and recognize the limitation of the available data.

Subsequently, a Cochrane review was led by Oxford Centre for Evidence Based Medicine professor Tom Jefferson. Jefferson and his team published the only Cochrane review based solely on raw unpublished regulatory data.30,31 Ultimately, the results of the review demonstrated Tamiflu shortened the duration of symptoms from the influenza virus by less than one day.

The struggle to acquire the data was nearly as eye-opening as the results, which I recount in “Remdesivir Is a Scam Like Tamiflu.” In a later editorial published in The BMJ,32 Ebell outlines some of the lessons learned from this multibillion-dollar fiasco.

These lessons included the need for all available data to be made public and available for independent reanalysis. He added the money spent on stockpiling medication is only minimally effective and may be better spent on other public health priorities.33

Flu Vaccine Ineffective and Increases Viral Shedding

During the 2019-2020 flu season, the CDC reported 51.8% of people 6 months old and older had been vaccinated against flu, representing a 3.1% increase from the previous season.34 According to the interim estimates from the CDC, the 2018-2019 flu vaccine overall adjusted effectiveness against infections associated with acute respiratory illness that required medical attention was 47%.35

The same statistics for the 2019-2020 flu vaccine revealed 45% effectiveness.36 However, said another way, the flu vaccine failed to offer any protection more than half the time it was given.

For adults over 50, which is the group most vulnerable to severe flu illness, the 2018-2019 vaccine had a mere 24% effectiveness rate against all influenza and an abysmal 8% effectiveness against influenza A, which is the most virulent type.37

The effectiveness of 2019-2020 flu vaccine was higher for those over 50 years but had dropped to 25% in adults 18 to 49 years.38 The vaccine has three or four type A or B strains. Even if those strains are a perfect match for the circulating viruses during a given flu season, it does not prevent many other respiratory infections. As noted by the Cochrane Collaboration:39

“Over 200 viruses cause ILI (influenza-like illness), which produces the same symptoms (fever, headache, aches, pains, cough and runny nose) as influenza. Without laboratory tests, doctors cannot distinguish between ILI and influenza because both last for days and rarely cause serious illness or death.”

In addition to poor performance, people who are routinely vaccinated shed 6.3 times more of the influenza virus into the air.40 In the study from the University of Maryland, researchers revealed that repeated vaccinations increased the amount of virus released with each breath, noting:41

“Little is known about the amount and infectiousness of influenza virus shed into exhaled breath. This contributes to uncertainty about the importance of airborne influenza transmission. We show that sneezing is rare and not important for — and that coughing is not required for — influenza virus aerosolization.”

This is important, as it means that even someone who’s not actively sneezing or coughing can potentially transmit the influenza virus to others. Further, someone who’s recently received the live attenuated influenza vaccine (LAIV) may also potentially actively shed and transmit the virus.

There is little evidence to suggest that getting an annual flu vaccine is a good way to combat influenza. On the contrary, there is mounting literature questioning the validity of this public health measure, which I discussed in “Is the Flu Vaccine Really ‘Working Well’ This Year?

At-Home Strategies to Reduce Risk of Viral Infections

There are strategies you can use at home to help prevent and treat the influenza virus if you are infected. In addition to protecting against flu, optimizing your vitamin D level also helps protect you against COVID-19.42 Studies have repeatedly demonstrated the track record for vitamin D in preventing respiratory infections, including a 2017 scientific review of 25 randomized controlled trials that concluded:43

“Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall. Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.”

As I discuss in a short video in “How Nebulized Peroxide Helps Against Respiratory Infections,” there is absolutely no question in my mind that nebulized hydrogen peroxide is the safest and most effective way to treat an acute upper respiratory infection.

I first wrote about this in the newsletter in April 2020 and have since received impressive testimonials from friends and acquaintances who got severely ill and used it. In the link to the article you can watch an interview with Dr. David Brownstein who has a clinic just outside Detroit.

At the time of the interview, he had successfully treated over 100 patients with nebulized hydrogen peroxide, having one patient hospitalized and no deaths. The treatment typically improves symptoms within hours.

In addition to using nebulized hydrogen peroxide at the first sign of a respiratory infection, I would also start taking quercetin and zinc to help fight the virus outside lung tissue. The earlier you start quercetin and zinc the more effective it will be since late in the course of the illness it is ineffective at inhibiting viral replication.

The key is to have everything you need available before flu season. An ounce of prevention is always worth a pound of cure. To read more about the relationship between quercetin and zinc, see “Zinc Is Key for COVID-19 Treatment and Prevention.”

– Sources and References

One Comment to Usnic Acid Inhibits Viral Respiratory Infection

  1. admin says:

    I use Zinc Chelate and Quercetin daily as part of my immunity strategy.

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