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 ten herbs in our Immunity loose leaf blend, along with a plain-language look at the peer-reviewed studies behind each one.
Elder Flower (Sambucus nigra Flos)
Laboratory testing found that black elderberry extract stimulates the production of inflammatory cytokines from human immune cells, supporting its traditional reputation for boosting the body's own defenses against infection. A separate study found that elderberry polysaccharides enhance the maturation of dendritic cells and their ability to stimulate T cells, key steps in mounting an effective immune response. A meta-analysis of randomized controlled trials confirmed that elderberry supplementation substantially reduces upper respiratory symptoms, consistent with a genuine immune-supportive effect rather than a purely antiviral one. 🔗 Cytokine production study · Dendritic cell/T cell study (PubMed) · Meta-analysis (PubMed)
Bay Leaf (Laurus nobilis)
Bay leaf has a long traditional use in the Mediterranean and Europe for immunological disorders, and laboratory research found that bay leaf extract modulates inflammatory signaling by suppressing activation of the NLRP3 inflammasome, an important regulator of the body's inflammatory immune response, while also reducing inflammatory cytokine expression in an animal model of acute lung injury. Separately, processed bay leaf extracts were shown to significantly downregulate excess interferon-gamma production in immune-stimulated human blood samples, indicating a genuine modulatory effect on human immune cell activity. Bay leaf essential oil has also demonstrated strong antibacterial activity against a range of clinically relevant pathogens, supporting its traditional role in fighting infection. 🔗 NLRP3 inflammasome study (PubMed) · Human immune cell study · Antibacterial activity review
Echinacea Flower and Leaf (Echinacea purpurea)
A meta-analysis of randomized controlled trials found that echinacea decreased the odds of catching a cold by 58%, one of the strongest pieces of clinical evidence available for any single herb in cold prevention. In the largest safety and efficacy trial of its kind, 755 healthy participants who took Echinacea purpurea over four months experienced fewer cold episodes, fewer total sick days, and specifically fewer colds caused by enveloped viruses, with the greatest benefit seen in those prone to recurrent infections. A related Cochrane review of preventive trials found that at least some echinacea preparations reduce the relative risk of catching a cold, reinforcing its traditional standing as an immune-supportive herb. 🔗 Meta-analysis · Large prevention trial (PubMed) · Cochrane review
Linden Flower (Tilia)
Laboratory research found that an aqueous extract of linden flowers stimulates the proliferation of lymphocytes, the white blood cells at the core of the adaptive immune response, at a range of concentrations. A more detailed study isolating the procyanidin compounds from linden flowers found that they decreased the production of reactive oxygen species from activated human neutrophils — the first line of the innate immune system's defense — while also inhibiting the release of the inflammatory signal IL-8. Linden flowers have long been used across Europe specifically to relieve the common cold, throat irritation, and upper respiratory tract disturbances, a traditional use these immune-cell findings help to explain. 🔗 Lymphocyte proliferation study · Human neutrophil study · Traditional respiratory use
Wild Thyme (Thymus serpyllum)
Wild thyme, officially recognized in the European Pharmacopoeia as Serpylli herba, has long been used as an immunostimulant, and research in an animal model of inflammatory bowel disease found that wild thyme extract improved disease severity as effectively as a standard reference medication, working by reducing pro-inflammatory cytokines including TNF-alpha, interferon-gamma, and IL-17. A review of wild thyme's nutritional and preventive health benefits confirmed antimicrobial and immunomodulatory effects across a range of laboratory and animal studies. Separately, wild thyme essential oil has demonstrated meaningful antibacterial activity against common pathogens, including E. coli and Staphylococcus species. 🔗 Immunomodulatory colitis study · Health benefits review (PubMed) · Antibacterial activity study
Olive Leaf (Olea europaea)
In a human study using peripheral blood cells from 25 healthy donors, olive leaf extract increased the absolute numbers of CD8+ and natural killer (NK) cells — key components of the body's defense against infected and abnormal cells — alongside increased production of interferon-gamma. In a real-world observational study conducted during the COVID-19 pandemic, people who regularly drank olive leaf tea had higher NK and NKT cell counts, higher interferon-gamma secretion, and more asymptomatic infections compared to non-drinkers. Separately, laboratory research found that olive leaf extract activates macrophages toward a more effective, infection-fighting state, increasing production of the immune-signaling molecule IL-12. 🔗 Human immune cell study · Observational study (PubMed) · Macrophage activation study
Calendula (Calendula officinalis)
Laboratory testing found that a novel calendula flower extract induced meaningful proliferation and activation of human peripheral blood lymphocytes, the white blood cells responsible for mounting a targeted immune response. Separately, methanol and ethanol extracts of calendula petals showed strong antibacterial activity against a broad panel of clinically relevant Gram-positive and Gram-negative bacteria, as well as excellent antifungal activity. In a randomized controlled clinical trial in cancer patients undergoing radiotherapy, a calendula flower extract mouthwash significantly reduced the severity of oral mucositis, a real-world demonstration of the plant's protective effect on vulnerable mucous membrane tissue. 🔗 Lymphocyte activation study (PubMed) · Antibacterial/antifungal study (PubMed) · Clinical trial (PMC)
Oregano (Origanum vulgare)
Carvacrol, oregano's main active compound, has been described in the pharmacological literature as a genuine immunomodulator, and a specially formulated carvacrol nanoemulsion was shown to modulate cytokine production in human peripheral blood mononuclear cells, reducing several inflammatory markers. A comprehensive review of oregano essential oil's biological activities beyond its antimicrobial effects found that it decreases production of pro-inflammatory cytokines while increasing the anti-inflammatory cytokine IL-10 in human macrophages. Separately, oregano essential oil was found to increase the content of antibody-forming lymphocytes in an animal model exposed to a physiological stressor, suggesting a genuine immune-enhancing property beyond its direct anti-inflammatory effects. 🔗 Human PBMC study (PubMed) · Biological activity review (PMC) · Immune-enhancing study (PMC)
Sage (Salvia officinalis)
A dedicated study isolated water-soluble polysaccharides from sage and found they had genuine immunomodulatory activity in a laboratory test used as a correlate of immune adjuvant activity, with several polysaccharide fractions showing particularly high mitogenic activity — the ability to stimulate immune cell proliferation. Separately, sage essential oil demonstrated immunomodulatory activity affecting both humoral (antibody-based) and cell-mediated immune responses in laboratory testing. A comprehensive human cell-system study of sage extract found dose-dependent effects across multiple inflammation and immune markers, with the most extensive activity observed in a model of wound healing and tissue remodeling. 🔗 Polysaccharide immunomodulatory study (PubMed) · Essential oil immunomodulatory study · Human cell system study (PMC)
Thyme (Thymus vulgaris)
Laboratory research using human macrophages found that thyme extract oils significantly reduced production of the pro-inflammatory mediators TNF-alpha, IL-1β, and IL-6, while substantially increasing the anti-inflammatory cytokine IL-10, indicating a genuine immune-balancing effect. A systematic review of thyme's ethnopharmacology and pharmacology confirmed a range of documented immunomodulatory activities alongside its well-known antibacterial and antiviral properties. Separately, thyme essential oil and its main compound thymol were shown to reduce oxidative stress and inflammatory signaling in human macrophages exposed to a bacterial toxin, supporting thyme's traditional role in protecting the respiratory system during infection. 🔗 Human macrophage cytokine study (PubMed) · Systematic review (PubMed) · Macrophage oxidative stress study (PMC)
Why This Matters
Each of these herbs has been studied individually for its effects on the immune system — largely in laboratory and human cell studies, with strong human clinical trial evidence for herbs like echinacea and elder, and real-world observational data for olive leaf. We combine them because their documented modes of action support immunity from several different angles: activating and balancing the white blood cells at the core of the immune response, modulating the inflammatory cytokines that coordinate the body's defense, and directly fighting the bacteria and viruses that cause common infections.
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 an autoimmune condition, are taking immunosuppressant medication, or are pregnant or breastfeeding, as several of these herbs have genuine, measurable effects on immune cell activity.