PLANT OF THE DAY brings you easy to digest information exploring science backed plants for health and medicine. Written by scientists, it aims to increase understanding of how effective plant medicine is as well as encourage simple dietary interventions to increase health and prevent disease. Plant of the day promotes the scientific research on select plant medicines and thereby helps bridge the gap between the worlds of plant medicine and general medicine.

DID YOU KNOW? While you can take, for example, a cup of chamomile tea to aid relaxation and sleep anytime, to treat a condition with a plant medicine it is important to take the correct dose and prescription for your individual needs – and in that case always first consult a NIMH medical herbalist and inform your healthcare provider before giving to a child, if you are pregnant, have any medical condition or are taking any medication.

Immune, respiratory and antimicrobial plant medicines – Thyme

Photography by David Taylor

Supporting immunity

Our innate immunity provides the initial response against pathogens like viruses and is a complex network that includes the inflammatory response. Inflammation response to infection involves mobilising inflammatory markers. These markers increase the presence of immune modulating cells, like white blood cells (also called leukocytes). And it’s the regulation of the initiation and extent of neutrophil (a type of leukocyte) and influx of cells such as lymphocytes (which produce antibodies) during inflammation that can determine both the success of pathogen elimination and the level of resulting tissue damage.

The respiratory system is particularly susceptible to oxidative-stress injury because of the large surface area associated with gas exchange. Oxidative stress injury includes damage to lung tissue, mucus hypersecretion, oedema of the bronchial wall, broncho-constriction and inflammation.

Among many approaches to supporting the immune system, inflammatory responses and respiratory function, are a range of effective plant medicines.

We can also help boost our innate immunity by simple lifestyle changes such as eating a rainbow diet, exercising to help lymphatic circulation (a crucial part of our immune response), getting outdoors daily to boost vitamin D, relaxing to prevent chronic stress and ensuring we rest and sleep well.

Supporting immunity with aromatic plants

Different plant medicines are used to support immunity and treat respiratory disorder in different parts of the globe, such as elder berry in Europe, echinacea in North America, and astragalus in Asia. We shall be exploring some of these in upcoming blogs. Aromatic plants though have a key role to play due to their essential or volatile oil. Volatile oils, as their name suggests, are the concentrated volatile ‘aromatic’ part of the plant (normally about 1-2% of a plant). You will be familiar with the scent of one of their active chemicals, camphor, inhaled from vapour rubs and present in eucalyptus and other aromatic plants.

Over the last 5 years studies on antibacterial, antiviral and antifungal volatile oils has more than tripled. Annual production of thyme essential oil alone (from several Thymus species) is estimated at 30 tonnes (with a value of around £1.2 million) and it is used in perfumes, cosmetics and widely in the food industry for flavour and improving shelf life by slowing oxidation and decreasing colour changes.

Essential oils and their chemical ingredients, have a long list of preventative actions (termed ‘anti-‘). They have been shown to be expectorant but also, anti-spasmodic, anti-tussive (cough), anti-histamine, anti-bacterial, anti-viral (including bay Laurus nobilis against SARS corona virus), anti-fungal and anti-oxidative and anti-inflammatory (by several mechanisms). Essential oils with anti-inflammatory activity act to reduce swelling and edema associated with respiratory infections and so reducing symptoms like wheezing, congestion and difficulty breathing. A combination of essential oils can act on different pathways to treat respiratory infection and on various levels.

The aromatic herb thyme is used as a plant medicine for inflammatory diseases and several studies show it contains valuable components to help treat respiratory disease by a number of different mechanisms. It is also antimicrobial and antiviral. Thyme is an aromatic plant and both extracts of the whole herb and its volatile oil have been shown active.

A brief profile of thyme extracted from Grow Your Own Physic Garden

  • The Plant

    Common Thyme Thymus vulgaris (synonyms) and related species.

    Thyme originates from the southern Mediterranean and Spain, Portugal, France, Germany, Italy, Morocco, Canada and the United States are now leading countries in thyme production. Common thyme (the Latin vulgaris means common/ widespread) is a low-growing woody perennial shrub with numerous branched stems, tiny shiny leaves and purple flowers which smell sharp and peppery (other thymes look and smell different like the variegated lemony lemon thyme).

    Though it doesn’t thrive in wet conditions it will survive in containers. Readily available forms are also cultivars of the wild thyme (T. serpyllum) with various stronger and different aromas. Needs to be cut back regularly to encourage new, non-woody growth.

  • Human Studies

    Most common species tested is Thymus vulgaris. Thyme species (with honey) reduces inflammation and polyp formation and promotes mucosal healing in chronic rhino-sinusitis. Together with primrose or ivy, it treats acute bronchitis and coughing. Immunostimulant in cancer patients. Controlled clinical trials show thyme is as effective as ibuprofen in reducing the severity of pain and spasm in dysmenorrhoea. Thyme has also been shown to improve ciliary beating in COPD (chronic obstructive pulmonary disease), plus other more recent reports show efficacy with other herbs in rhinosinusitis.

  • Laboratory Studies

    ANTIMICROBIAL Activity against numerous different types of fungus, bacteria, including methicillin resistant Staphylococcus aureus (MRSA) and virus including noro virus and herpes.

    RESPIRATION Antispasmodic (B2 adrenergic) and expectorant, increases ciliary activity – helps bronchial cilia to clear away mucous. Thyme demonstrates significant positive effect on the smooth muscles of trachea and on respiratory clearance.

    INFLAMMATION Thyme extracts decrease pro-inflammatory cytokines and increase anti-inflammatory secretion in activated macrophages. Extracts (T. zygis subsp. sylvestris) and essential oil reduces production (and gene expression) of several inflammatory mediators (NF-кB, COX-2, iNOS and TNF-α protein) and have been shown superior to that of the drug dexamethasone. The main thyme compounds carvacrol, thymol and p-cymene lowered oxidation without decreasing cell viability. Thyme has been considered as a natural substitute for chemical anti-inflammatory medicines such as dexamethasone, which may have serious adverse effects (including an increase in infection and delayed wound healing).

    NEUROACTIVITY Thymol, one of the ingredients in the volatile oil acts on the brain’s calming inhibitory (GABA) receptors and acts positively on brain and liver functions in models of alcoholism.

    Other effects in the lab include lowering blood pressure, serum lipids and obesity.

  • Historical Use

    Folklore Thyme’s name is derived from the Greek word thumus, meaning courage or spiritedness and it was believed to instil courage and strength. Roman soldiers would bathe in thyme before going into battle. In the middle ages, English ladies commonly embroidered an emblem of a bee hovering over a sprig of thyme onto the scarves they gave their knights. Scottish highlanders also used the herb to prepare for battle and prevent nightmares.

    What physicians of old said English herbalist Gerard said it would cure ‘pains in the head’ and Culpepper that ‘it purgeth the body of phlegm and is an excellent remedy for shortness of breath. It is so harmless you need not fear the use of it.’

    Plant Medicine use Decongestant and expectorant for coughs, mild sedative, for epilepsy and migraine and for hangovers and reducing nightmares. Widely reported to improve respiratory and gastric functions in farm animals (sheep, goats, and chickens) and horses.

  • Use the herb for health

    Dose 3-10g dried leaves daily.

    Leaves are used to prepare steam inhalations, nasal sprays, gargles, teas (lemon thyme, T. citriodorus, being particularly fragrant), syrups and tinctures. Inhalation of steam from a few drops of essential oil added to hot water for colds (in France, where essential oils are often taken in suppositories, 1 drop of Thymus vulgaris is placed at the back of the tongue morning and night (using a cotton bud) at the first sign of an infection, but essential oils are not taken internally in the UK, except in controlled clinical trials).

    Used in cooking with almost anything to flavour dressings, vegetables, pasta, fish, meat, stew, soup and many Italian dishes.

  • Key ingredients

    Phenolic acids like rosmarinic acid, flavonoids such as luteolin and apigenin, biphenyl compounds (2 ring aromatics) and a volatile oil.

    Thyme contains between 1% and 2.5% volatile oil giving it its spicy taste and pleasant aroma. Thymol and (its phenol isomer) carvacrol, are the main components of the oil (Thymus vulgaris, T. serpillum, and T. capitatus  30–50%). These compounds have radical scavenging (antioxidant), antitussive, expectorant, antispasmodic (broncholytic), anti-inflammatory, antifungal, antibacterial and antiviral effects (as do other components of essential oils from other aromatic plants).

    Antimicrobial activity may be based on additive effects. Carvacrol antimicrobial activity is higher than that of other volatile compounds present in essential oils due to the presence of the free hydroxyl group, hydrophobicity, and the phenol moiety. The oil also contains borneol and linalool – up to 5%.

    Time of leaf harvest, climate, vegetative development stage, and extraction method can all vary the chemical nature of the extracted leaf – this is why it is important to ensure plant material is harvested at the correct time and that products are purchased only from an established reputable standardised source or from your local NIMH registered medical herbalist.


  • Safety

    Safety Human trials refer to excellent safety profile and tolerance of the whole herb. Safe for children in moderation, for example cooled tea added to babies’ baths. Individual ingredients may cause allergic reaction, such as dermatitis or inflammation of the skin and after consumption of thymol. Thyme herb is given GRAS (generally recognised as safe) status. Do not exceed oral doses of 10g of dried leaves (0.03% of phenols calculated as thymol) per day to prevent toxicity.

    Essential oils (and the chemical ingredients) from several Thymus species have been attracting considerable interest due to recognition of their safety and they are used in the pharmaceutical, food and cosmetic industry and a number are given GRAS status. That said, essential oils are very potent medicines, must be sourced responsibly as they can be adulterated. Some essential oils are toxic and must never be used and none should be applied topically without dilution to maximum 5% and used for a short duration of time such as one week.

Scientific sources

Begrow F, Engelbertz J, Feistel B, Lehnfeld R, Bauer K, Verspohl EJ. Impact of thymol in thyme extracts on their antispasmodic action and ciliary clearance. Planta Med. 2010;76(4):311–318. doi:10.1055/s-0029-1186179

Büechi S, Vögelin R, von Eiff MM, Ramos M, Melzer J. Open trial to assess aspects of safety and efficacy of a combined herbal cough syrup with ivy and thyme. Forsch Komplementarmed Klass Naturheilkd. 2005;12(6):328–332. doi:10.1159/000088934

Büechi S, Vögelin R, von Eiff MM, Ramos M, Melzer J. Open trial to assess aspects of safety and efficacy of a combined herbal cough syrup with ivy and thyme. Forsch Komplementarmed Klass Naturheilkd. 2005;12(6):328–332. doi:10.1159/000088934

Direkvand-Moghadam A, Khosravi A. The impact of a novel herbal Shirazi Thymus Vulgaris on primary dysmenorrhea in comparison to the classical chemical Ibuprofen. J Res Med Sci. 2012;17(7):668–670.

Fani M, Kohanteb J. In Vitro Antimicrobial Activity of Thymus vulgaris Essential Oil Against Major Oral Pathogens. J Evid Based Complementary Altern Med. 2017;22(4):660–666. doi:10.1177/2156587217700772

Gilling DH, Kitajima M, Torrey JR, Bright KR. Antiviral efficacy and mechanisms of action of oregano essential oil and its primary component carvacrol against murine norovirus. J Appl Microbiol. 2014;116(5):1149–1163. doi:10.1111/jam.12453

Hofmann D, Hecker M, Völp A. Efficacy of dry extract of ivy leaves in children with bronchial asthma–a review of randomized controlled trials. Phytomedicine. 2003;10(2-3):213–220. doi:10.1078/094471103321659979

Iten F, Saller R, Abel G, Reichling J. Additive antimicrobial [corrected] effects of the active components of the essential oil of Thymus vulgaris–chemotype carvacrol [published correction appears in Planta Med. 2009 Sep;75(11):1236]. Planta Med. 2009;75(11):1231–1236. doi:10.1055/s-0029-1185541

Kemmerich B, Eberhardt R, Stammer H. Efficacy and tolerability of a fluid extract combination of thyme herb and ivy leaves and matched placebo in adults suffering from acute bronchitis with productive cough. A prospective, double-blind, placebo-controlled clinical trial. Arzneimittelforschung. 2006;56(9):652–660. doi:10.1055/s-0031-1296767

Lai WL, Chuang HS, Lee MH, Wei CL, Lin CF, Tsai YC. Inhibition of herpes simplex virus type 1 by thymol-related monoterpenoids. Planta Med. 2012;78(15):1636–1638. doi:10.1055/s-0032-1315208

Lang C, Röttger-Lüer P, Staiger C. A Valuable Option for the Treatment of Respiratory Diseases: Review on the Clinical Evidence of the Ivy Leaves Dry Extract EA 575®. Planta Med. 2015;81(12-13):968–974. doi:10.1055/s-0035-1545879

Loizzo MR, Saab AM, Tundis R, et al. Phytochemical analysis and in vitro antiviral activities of the essential oils of seven Lebanon species. Chem Biodivers. 2008;5(3):461–470. doi:10.1002/cbdv.200890045

Lorenzo JM, Mousavi Khaneghah A, Gavahian M, et al. Understanding the potential benefits of thyme and its derived products for food industry and consumer health: From extraction of value-added compounds to the evaluation of bioaccessibility, bioavailability, anti-inflammatory, and antimicrobial activities. Crit Rev Food Sci Nutr. 2019;59(18):2879–2895. doi:10.1080/10408398.2018.1477730

Ludwig S, Stier H, Weykam S. Evaluation of Blood Alcohol Concentrations after Oral Administration of a Fixed Combination of Thyme Herb and Primrose Root Fluid Extract to Children with Acute Bronchitis. Drug Res (Stuttg). 2016;66(2):69–73. doi:10.1055/s-0034-1398543

Marzian O. Behandlung der akuten Bronchitis bei Kindern und Jugendlichen. Anwendungsbeobachtung bestätigt Nutzen und Unbedenklichkeit einer Flüssigextrakt-Kombination aus Thymiankraut und Efeublättern [Treatment of acute bronchitis in children and adolescents. Non-interventional postmarketing surveillance study confirms the benefit and safety of a syrup made of extracts from thyme and ivy leaves]. MMW Fortschr Med. 2007;149(27-28 Suppl):69–74.

Nabissi M, Marinelli O, Morelli MB, et al. Thyme extract increases mucociliary-beating frequency in primary cell lines from chronic obstructive pulmonary disease patients. Biomed Pharmacother. 2018;105:1248–1253. doi:10.1016/j.biopha.2018.06.004

Qadir MI, Parveen A, Abbas K, Ali M. Analgesic, anti-inflammatory and anti-pyretic activities of Thymus linearis. Pak J Pharm Sci. 2016;29(2):591–594.Sharifi-Rad M, Varoni EM, Iriti M, et al. Carvacrol and human health: A comprehensive review. Phytother Res. 2018;32(9):1675–1687. doi:10.1002/ptr.6103

Sharifi-Rad J, Salehi B, Schnitzler P, et al. Susceptibility of herpes simplex virus type 1 to monoterpenes thymol, carvacrol, p-cymene and essential oils of Sinapis arvensis L., Lallemantia royleana Benth. and Pulicaria vulgaris Gaertn. Cell Mol Biol (Noisy-le-grand). 2017;63(8):42–47. Published 2017 Aug 30. doi:10.14715/cmb/2017.63.8.10

Toujani MM, Rittà M, Civra A, et al. Inhibition of HSV-2 infection by pure compounds from Thymus capitatus extract in vitro. Phytother Res. 2018;32(8):1555–1563. doi:10.1002/ptr.6084

Wienkötter N, Begrow F, Kinzinger U, Schierstedt D, Verspohl EJ. The effect of thyme extract on beta2-receptors and mucociliary clearance. Planta Med. 2007;73(7):629–635. doi:10.1055/s-2007-981535

Wińska K, Mączka W, Łyczko J, Grabarczyk M, Czubaszek A, Szumny A. Essential Oils as Antimicrobial Agents-Myth or Real Alternative?. Molecules. 2019;24(11):2130. Published 2019 Jun 5. doi:10.3390/molecules24112130