The therapeutic use of essential oils for immune health dates back to ancient Egyptian, Chinese, Greek, Indian, and Roman civilizations, (17) and their use has especially grown in popularity in North America over the last several decades. (17) Essential oils contain hundreds of different constituents, (23) and researchers continue to examine how these components may benefit the immune system. Keep reading to learn which essential oils demonstrate antimicrobial, antibacterial, antifungal, antioxidant, and antiviral activities. (22)(23)
What are essential oils?
Essential oils (EOs) are highly concentrated aromatic oils sourced from the bark, leaves, stems, fruit, and flowers of plants. They can be extracted through different methods such as steam distillation or solvent extraction. (22)
Essential oils are commonly used in aromatherapy, a complementary therapy that involves the inhalation of plant extracts to promote physical and emotional health. (1) Aromatherapy may include mixing essential oils with a carrier oil such as coconut or jojoba and applying them directly to the skin through massage, or through inhalation by using an electronic diffuser to disperse tiny particles of EO and water into the air. (1)(2)
EOs contain volatile secondary metabolites (fragrant compounds that help attract pollinators and protect the plants from pests) that contribute to the beneficial therapeutic effects of EOs. These volatile metabolites have a low molecular weight and high vapor pressure, and as a result, they evaporate easily. (1)(26) The main volatile components of essential oils are called terpenes, which are aromatic compounds found in plants. Monoterpenes and sesquiterpenes are the most common aromatic components in essential oils. (8)(28)
Did you know? The scent of a plant’s EOs attracts pollinators and protects it from unwanted pests. (18)
Essential oils for immune health
The biological effects of essential oils on humans are complex; however, research continues to examine the immunomodulatory properties of EOs and their potential application in infectious diseases. (1)(12) Several studies have demonstrated that certain EOs have potential antimicrobial, antifungal, anti-inflammatory, and antiviral benefits that may be beneficial to the immune system. (22)
About your immune system
The immune system is composed of various cells that protect us from different types of threats such as physical injuries and pathogens. (20) The immune system can be divided into two categories: innate and adaptive immunity. Innate immunity, the body’s first defense against an intruder, includes physical and chemical barriers, such as the skin and stomach acid, and responds quickly to threats.
Comparatively, the adaptive immune system responds more slowly and prevents us from getting sick in the future, (20) as it involves specialized systemic cells that eliminate pathogens the body has previously encountered. (20)
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Beneficial properties of essential oils for immune health
The immune-supportive potential of EOs depends on the chemical constituents found in the EO. More controlled research studies on humans are necessary to examine the benefits of essential oils on human immune function. However, available in vitro studies on essential oils can provide important insights.
The antimicrobial potential of essential oils depends on the different biochemical reactions that occur within the bacterial cell. (23) Because EOs are lipophilic (easily able to dissolve in fat), their chemical constituents can easily penetrate bacterial cell membranes and disrupt processes such as energy generation, nutrient processing, and the synthesis of structural molecules. (23)
EOs that show antimicrobial activity include:
These EOs may target potentially harmful bacteria such as Listeria monocytogenes, Bacillus sphaericus, Enterobacter aerogenes, Escherichia coli, and Shigella flexneri. (23)
Researchers have demonstrated that certain essential oils may disrupt the cell wall of different fungi, thereby killing the fungus. One possible mechanism is that essential oils penetrate the mitochondrial membranes of fungal cells, affecting their electron transport system and, in turn, disrupting the protein, lipid, and nucleic acid content of the fungal cells. (23)
EOs that show antifungal activity include:
- Thyme (23)
These EOs may target fungi such as Candida acutus, C. albicans, C. tropicalis, Rhodotorula rubra, and Saccharomyces cerevisiae. (23)
The antiviral potential of essential oils continues to be studied. Certain EOs may interfere with the viral envelope (protective outer layer of a virus), inhibiting the virus from replicating, as well as disrupting other key functions. (23)
Antiviral essential oils include:
- Eucalyptus oil
- Tea tree oil
- Thyme oil (23)
Studies indicate that these EOs may target the herpes simplex virus type 1 and 2, rhinovirus, influenza virus, adenovirus type 3, as well as other viruses. (23)
5 essential oils for immune system health
Several essential oils have immune-supportive capabilities. These capabilities depend on the chemical composition of the EO, which can vary depending on the region in which the plant was grown and the oil extraction methods used. (28) The following five essential oils demonstrate one or more of the effects related to immune system health discussed above.
1. Clove essential oil
Clove essential oil is sourced from the dried flower buds of clove trees belonging to the Myrtaceae family of plants native to Indonesia. (4)(6) Clove EO has demonstrated immune-supportive capabilities including anti-inflammatory, antimicrobial, antioxidant, and antifungal activities. (4)
The main components of clove essential oil are phenylpropanoids, which include carvacrol, thymol, eugenol, and cinnamaldehyde. These and other compounds found in clove EO, such as terpenes and flavonoids, have demonstrated immune-supportive capabilities. (4)
In an in vitro study, researchers evaluated the effect of clove essential oil on 17 protein biomarkers that play a role in inflammation and tissue healing using a system that mimicked a disease microenvironment of inflamed skin cells. They observed that at specific concentrations, clove EO reduced the spread of the diseased connective tissue cells and exhibited fewer pro-inflammatory biomarkers. (4) Their research suggests that clove essential oil may have anti-inflammatory and tissue remodeling properties on human connective tissue cells. (13)
In another study, clove essential oil was given orally to mice who had been immunized with blood cells from another animal. Results demonstrated that, depending on the dose, important functions of the adaptive immune response of the mice were restored and that clove EO stimulated the immune system of the mice. (13)
2. Eucalyptus essential oil
Eucalyptus essential oil is sourced from the leaves of Eucalyptus globulus trees of the Myrtaceae family of plants native to Australia. Eucalyptus essential oil benefits include immune-supportive capabilities such as anti-inflammatory, antioxidant, and antibacterial activities. (7) The main compound with immune-supportive capabilities found in eucalyptus EO is a monoterpene called 1,8-cineole. (7)
In an in vitro study, researchers found that Eucalyptus globulus EO demonstrated antimicrobial activity against Escherichia coli (bacteria involved in the development of urinary tract infections and diarrhea) and Staphylococcus aureus, a bacteria involved in the development of serious skin infections. These findings could contribute to further research examining the use of natural antibiotic options for addressing diseases related to these two types of bacteria such as pneumonia, endocarditis (infection of the heart valves), and bone infections. (3)(29)
In an animal study using both in vivo and in vitro methods, researchers examined the influence of eucalyptus EO on innate immune cells and determined that eucalyptus EO activated phagocytosis, a process by which innate immune cells destroy microbial pathogens and apoptotic cells. (25)(27)
3. Oregano essential oil
Oregano essential oil is sourced from the leaves, stems, and flowers of the oregano plant, which is native to parts of Europe and Asia. (19) Oregano EO has demonstrated immune-supportive capabilities including antimicrobial, antifungal, antiparasitic, antioxidant, anti-inflammatory, and antitumor effects. (19) The primary immune-supportive constituents of oregano essential oil are carvacrol and thymol. (19)
Oregano essential oil can disturb the cell wall integrity of fungus cells by interfering with the synthesis of ergosterol (a sterol found in the cell membranes of fungi). Sterols are found in living organisms and help maintain fluidity of cell membranes and regulate biological processes. (10)(19) An in vitro study demonstrated that oregano essential oil may be useful as an antifungal against Candida glabrata, a common strain of yeast present in humans that may cause a fungal infection for some people, especially those with a compromised immune system. (32)
Another study using in vitro methods demonstrated that oregano essential oil may inhibit the release of pro-inflammatory cytokines (proteins involved in inflammatory and neuropathic pain) (34) and influence the expression of inflammatory genes. (19)
4. Lemon essential oil
Lemon essential oil is sourced from the peels of lemons grown from trees that are native to South Asia and belong to the Rutaceae family of plants. (15) Lemon essential oil benefits related to the immune system are attributed to its antioxidant, antimicrobial, anti-stress, and antibacterial activity. (9)(33)
The major constituents of lemon essential oil are d-limonene, b-pinene, and y-terpinene. Other terpenes, flavonoids, carotenes, and coumarins may also contribute to its antioxidant activity. (5)(9)
A study using in vitro methods demonstrated that constituents of lemon essential oil, including limonene, may contribute to apoptosis activity in leukemic (cancer) cells (HL-60). (14) Apoptosis is a vital process of the immune system that involves programmed cell death and normal cell turnover. (11)
Lemon essential oil may also have anti-stress effects. Stress is the body’s response to a threat that’s either real or perceived, and too much stress can negatively affect the immune system (21)(30) In a study involving mice, inhalation of lemon essential oil vapor was shown to influence neurotransmitters that affect mood and have anti-stress effects. (16)
5. Rosemary essential oil
Rosemary essential oils are sourced from the leaves, stems, and flowers of the rosemary shrub, which is part of the Lamiaceae family of plants. The main constituents of rosemary essential oil that contribute to immune support benefits are 1,8-cineole, a-pinene, and camphor.
In one study that involved administering rosemary EO into the mouths of mice, researchers found evidence that the chemical compounds in rosemary essential oil, such as 1,8-cineole, a-pinene, and camphor, may be hepatoprotective (prevent liver damage). (24) The same study demonstrated that rosemary essential oil has antioxidant activity and can neutralize free radicals. (24)
In another animal study, researchers examined the effects of rosemary essential oil on rats by administering the EO, and using immune system markers such as leukocyte migration. Results demonstrated that rosemary EO may have anti-inflammatory capabilities. (31)
The bottom line
Various essential oils sourced from plants, including clove, lemon, eucalyptus, oregano, and rosemary, may have important immune-supportive capabilities. The therapeutic effects found in essential oils can vary based on their chemical composition, region origin, and extraction methods. Researchers continue to examine how specific essential oils support innate and adaptive immune system responses through their demonstrated antimicrobial, antifungal, antiviral, anti-inflammatory, or antioxidant properties. If you’re a patient, speak to your integrative healthcare practitioner about including essential oils for immune health in your wellness plan.
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I’m really interested in essential oils