Herbal traditions have used these plants for centuries, but we like to go a step further and look at what modern research actually shows. Below are nine herbs in our antiviral blend, along with a plain-language look at the peer-reviewed studies behind each one.
Holy Basil / Tulsi (Ocimum sanctum)
Extracts of Tulsi leaves have shown anti-herpes activity at multiple stages of the viral replication cycle in laboratory testing against herpes simplex virus. Eugenol, a compound isolated from Tulsi using supercritical fluid extraction, has also been identified as a potent inhibitor of dengue virus serotype 2 (DENV-2), a mosquito-borne virus with no approved antiviral treatment. Separately, Tulsi leaf extracts showed dose-dependent antiviral efficacy against the H9N2 avian influenza virus in an egg-based infection model, working at the virucidal, therapeutic, and prophylactic stages. 🔗 Anti-herpes study · Dengue/eugenol study (PMC) · Influenza H9N2 study (PMC)
Elder Flower (Sambucus nigra flos)
A lyophilized infusion made from elder flowers (alongside St. John's Wort and soapwort) inhibited the reproduction of influenza A and B virus strains both in vitro and in vivo, as well as herpes simplex virus type 1, in classic pharmacological testing. A more recent comparative study found that purified elder flower extract had inhibitory activity against herpes simplex virus type 2 (HSV-2) replication, alongside leaf and fruit extracts of the same plant. Elder flower extract has also demonstrated the ability to block the binding between the SARS-CoV-2 spike protein and the human ACE2 receptor in vitro, a key first step of infection. 🔗 Influenza/HSV-1 study · HSV-2 study · SARS-CoV-2 study
Ginkgo (Ginkgo biloba)
Ginkgo leaf extracts have shown anti-influenza virus activity in laboratory testing, contributing to a broader body of research on the plant's antimicrobial properties. Separately, Ginkgo biloba extract (EGb) demonstrated a remarkable anti-herpesvirus effect against both HSV-1 and HSV-2, with pretreatment of the viruses before infection producing the strongest results — largely attributed to the flavonoid isorhamnetin. A nanoemulsion of polyprenols isolated from ginkgo leaves also showed antiviral activity against influenza A (H3N2) and hepatitis B virus in vitro. 🔗 Anti-influenza study (PubMed) · Anti-herpesvirus study (PMC) · Influenza H3N2/hepatitis B study (PMC)
Lemon Balm (Melissa officinalis)
A hydroalcoholic extract of lemon balm leaves reduced the cytopathic effect of herpes simplex virus type 2 (HSV-2) on cell cultures, working through a mechanism that takes effect after the virus has entered the cell. In a separate study, an aqueous Melissa extract showed high virucidal activity against HSV-1 even at very low concentrations, blocking the virus's attachment to host cells before infection could begin. More recently, a range of Melissa extracts were tested against modern respiratory viruses, with the water extract showing significant inhibitory effects against both SARS-CoV-2 and MERS-CoV, and the methanol extract showing strong activity against influenza A (H1N1). 🔗 HSV-2 study (PubMed) · HSV-1 attachment study (PubMed) · SARS-CoV-2/MERS/H1N1 study (PMC)
Calendula (Calendula officinalis)
A tincture made from calendula flowers suppressed the replication of herpes simplex virus and two strains of influenza A virus (A2 and APR-8) in classic in vitro testing. Later research found that organic extracts of calendula flowers exhibited potent anti-HIV activity, inhibiting HIV-1 reverse transcriptase in a dose- and time-dependent manner and protecting uninfected cells from virus-induced cell fusion and death. More recent in silico studies have also identified flavonoid compounds in calendula — including rutin and isorhamnetin — as promising candidates for inhibiting the SARS-CoV-2 main protease. 🔗 Influenza/herpes study (PubMed) · Anti-HIV study (PubMed) · SARS-CoV-2 review
Olive Leaf (Olea europaea)
An elenolic acid-rich olive leaf extract demonstrated dose-dependent anti-influenza virus activity by inhibiting neuraminidase, an enzyme the virus needs to spread between cells. Computational and laboratory studies have also identified olive leaf extract as a potent inhibitor of HIV-1, binding to the fusion protein gp41 that the virus uses to enter human cells, with effective concentrations well below toxic levels. In a randomized, triple-blinded clinical trial in hospitalized COVID-19 patients, olive leaf extract improved clinical status and reduced the length of hospitalization compared to placebo. 🔗 Anti-influenza study (PubMed) · Anti-HIV gp41 study (PubMed) · COVID-19 clinical trial (PubMed)
Oregano (Origanum vulgare)
Oregano oil and its primary active compound, carvacrol, were shown to specifically inhibit HIV and simian immunodeficiency virus (SIV) by blocking the fusion of the virus with target cells, regardless of viral tropism. Separately, oregano oil and carvacrol produced statistically significant reductions in the infectivity of murine norovirus — a human norovirus surrogate — within just 15 minutes of exposure, acting directly on the virus's protein shell and RNA. Commercial oregano oils have also demonstrated anti-influenza virus activity against the H1N1 strain in laboratory testing, alongside pure carvacrol. 🔗 HIV/SIV study (PubMed) · Norovirus study (PubMed) · Influenza study
Sage (Salvia officinalis)
Aqueous and ethanolic extracts of sage showed high virucidal activity against free herpes simplex virus type 1 and type 2 in laboratory testing, with the strongest extract reducing plaque formation by more than 90% for HSV-1 and 99% for HSV-2. Separately, aqueous sage extract showed potent anti-HIV-1 activity in T-cell lines, primary macrophages, and tonsil tissue cultures, working by impairing the virus's ability to fuse with and enter target cells. A specially tailored sage extract, Faramir®, more recently demonstrated antiviral activity against SARS-CoV-2, influenza, and HIV in the same set of experiments. 🔗 Herpes virus study (PubMed) · Anti-HIV-1 study (PMC) · SARS-CoV-2/influenza/HIV study
Stinging Nettle (Urtica dioica)
Aqueous extracts of stinging nettle inhibited the development of syncytia (fused, virus-damaged cells) in cultures infected with feline immunodeficiency virus, a close relative of HIV used as a laboratory model. Separately, methanolic nettle extract inhibited the replication of dengue virus serotype 2 in cell culture testing. More recently, a carbohydrate-binding protein isolated from nettle rhizomes (Urtica dioica agglutinin) was shown to be a potent, broad-spectrum inhibitor of SARS-CoV-2, blocking the fusion step of infection across multiple viral variants, including Delta and Omicron. 🔗 FIV/antiviral screening study (PubMed) · Dengue virus study (PubMed) · SARS-CoV-2 study (PMC)
Why This Matters
Each of these herbs has been studied individually for antiviral properties — largely in vitro, with a smaller number of animal and human clinical studies. Findings from lab and animal models don't always translate directly to the same effects in people. We combine these herbs because their documented modes of action target viruses through different mechanisms and at different stages of infection, from blocking viral entry and fusion to disrupting replication once a virus is already inside a cell.
This post is for educational purposes and summarizes existing scientific literature. It is not medical advice, and our blend is not intended to diagnose, treat, cure, or prevent any disease. Please consult a healthcare provider before using herbal supplements, especially if you have a viral infection or underlying health condition.