Thyme

Thymus vulgaris L. sits in Lamiaceae, the mint family, in subfamily Nepetoideae and tribe Mentheae. NCBI Taxonomy files it as taxon 49992. Linnaeus published the name in Species Plantarum (volume 2, page 591, 1 May 1753); IPNI records it as 461765-1. Plants of the World Online gives the native range as south-western Europe and south-eastern Italy—Spain, the Balearics, France, and Italy—with introductions in Britain, central Europe, Algeria, the Caribbean, and New Zealand. It is a low woody subshrub, usually under a foot tall, with wiry branching stems, small evergreen grey-green leaves, and whorls of tiny white, pink, or pale purple two-lipped flowers from late spring into summer. It wants sun, lean soil, and drainage. The commercial crop is both cultivated and wild-collected, much of it picked by hand because the plant grows so low.

Thymus zygis L., Spanish thyme, is native to the Iberian Peninsula and is used interchangeably with garden thyme in medicine. EMA and the European Pharmacopoeia accept either species, or a mixture, as Thymi herba, and the US list of GRAS essential oils names T. vulgaris and T. zygis var. gracilis together. Thymus serpyllum L. is the creeping wild thyme of Europe. Its drug, Serpylli herba, has a European Pharmacopoeia quality monograph (at least 3.0 ml/kg essential oil) and a 1987/1990 German Commission E monograph for upper-respiratory catarrh at an average 6 g of herb per day, but EMA’s herbal committee has not adopted a harmonised monograph for it (Jalil, Pischel, Feistel and colleagues, Frontiers in Nutrition 2024). The American Botanical Council’s Commission E translation adds that T. pulegioides and T. praecox subsp. arcticus are sold as, or mixed with, wild thyme. The genus is large and full of ornamental and culinary cousins. They are not the trial material.

Chemotypes are where thyme gets interesting. Thompson, Chalchat, Michet, Linhart, and Ehlers (Journal of Chemical Ecology 2003) describe T. vulgaris as chemically polymorphic, with six chemotypes that segregate spatially in nature: two phenolic types, thymol and carvacrol, and four non-phenolic types—geraniol, α-terpineol, linalool, and thuyanol. Many wild populations hold two or three chemotypes at once. The phenolic types sit at the end of the biosynthetic chain and carry large amounts of their precursors, γ-terpinene and p-cymene, so their dominant compound makes up a smaller share of the oil. EMA’s assessors note that only the thymol type meets the pharmacopoeial definition of thyme. A soft, linalool-type oil sold for aromatherapy and a pharmacopoeial thymol-type oil can both say Thymus vulgaris on the label. They are not the same product.

Chemistry. The dried herb holds up to 2.5% essential oil, led by thymol (PubChem CID 6989) and its isomer carvacrol (CID 10364). Both are C10H14O monoterpene phenols that differ only in where the hydroxyl group sits on the ring. p-Cymene, γ-terpinene, linalool, β-myrcene, and terpinen-4-ol fill out the oil. The non-volatile side includes rosmarinic and caffeic acid derivatives, flavones such as luteolin and apigenin, methylated flavones such as cirsilineol and thymonin, up to 8% polysaccharides, and ursolic and oleanolic acid triterpenes. Extracts carry far less thymol than the oil: EMA’s assessors cite a German-pharmacopoeia liquid extract at 0.038% thymol and dry extracts below the detection limit, yet those low-thymol extracts were still antispasmodic in isolated-organ models. That is the first hint that thyme’s cough pharmacology is not only a thymol story.

The name is older than the pharmacology. HerbalGram’s 2008 thyme profile offers two Greek roots: thyo, perfume, and thumus, courage and strength. Spice references prefer a fumigation reading and point to thyme burned as temple incense. In ancient Greece, to smell of thyme was praise for someone with style. The Romans flavoured cheeses and liqueurs with it. Medieval ladies, the story goes, gave knights scarves embroidered with a bee hovering over a sprig of thyme as a token of courage; that is folklore repeated in herb histories, and this page repeats it as folklore. A 2011 American Chemical Society note says Egyptians used a thyme preparation in mummification. The line circulates widely, but this monograph could not trace it to primary archaeological evidence, so treat it as lore rather than a documented recipe.

The chemistry history is better documented. In 1719 Caspar Neumann, a Berlin court apothecary and chemistry professor, distilled thyme oil and noticed a white crystalline solid separating from it. He called it camphora thymi, camphor of thyme, and later described it in the Royal Society’s Philosophical Transactions. Alexandre Lallemand named the compound thymol in 1853 and worked out its formula. Thymol moved through pharmacy as an antiseptic and a vermifuge. EMA’s assessors note that folk vermifuge doses of 0.3–0.6 g of thymol—far beyond anything in thyme tea—caused abdominal pain and transient collapse. Eventually synthetic thymol became cheaper than distilling it from thyme. Listerine’s fixed blend of thymol, eucalyptol, menthol, and methyl salicylate is now the place most people meet thyme’s phenol without knowing it.

The regulatory history is a list of different products sharing one plant. Germany’s Commission E approved thyme herb in 1984 (revised 1990 and 1992) for symptoms of bronchitis and whooping cough and for catarrh of the upper airways. EMA’s herbal committee adopted a thyme monograph in 2007 and revised it in 2013, settling on traditional use in productive cough associated with a cold. Thyme oil got its own traditional monograph in 2010, revised in 2020, with a periodic review opened in 2026. The thyme–primula combination has a separate monograph, current revision published in 2016, in which some fixed combinations are well-established in adults and others traditional. Health Canada’s 2008 monograph took a broader traditional view, including gargles for sore mouth and throat. In the United States thyme is a GRAS spice and essential oil, thymol sits in OTC mouthwash, and thymol products are registered with the EPA against varroa mites in beehives.

EMA does not require pharmacology for a traditional-use monograph, and its thyme files say so. The assessment report still collects plausible mechanisms. Thyme extracts and thymol relax tracheal and intestinal smooth muscle in isolated-organ studies, and thymol shows agonist activity at α- and β-adrenergic receptors in vitro. Begrow and colleagues (2010) found that extracts with almost no thymol were still antispasmodic, though thymol-rich extract did better in rat ciliary-transport experiments. Thymol is a positive allosteric modulator of GABA-A receptors in vitro. Thymol and carvacrol are broadly antimicrobial against bacteria, yeasts, and fungi such as Candida albicans in dish assays. EMA’s combination summary puts it plainly: laboratory work suggests thyme may act against microbes and relax muscle, while primula root may increase sputum production and help bring up phlegm. That is a reasonable expectorant-and-antispasmodic story. It is not a demonstrated human mechanism.

Exposure matters. Kohlert and colleagues (2002) gave a single oral dose of thyme dry extract supplying 1.08 mg of thymol: only thymol sulfate appeared in plasma, peaking at about two hours, with an elimination half-life near 10 hours. EMA’s assessors estimate that recommended herb preparations deliver roughly 38 mg of thymol a day, while 25 drops of pure oil would deliver about 300 mg. In vitro, thymol and carvacrol are metabolised mainly by CYP2A6. A methylated flavone reported from thyme inhibits CYP1A2 and CYP3A4 in dishes, but nobody has measured how much of it garden thyme contains, and EMA judged the clinical relevance minimal without case reports. Mouthwash is a different exposure entirely: the four-oil rinse is swished for 30 seconds against plaque biofilm and spat out. Drinking thyme tea does not reproduce that.

Combinations complicate attribution. In thyme-ivy and thyme-primrose products, the second plant is itself a traditional expectorant. When a combination beats placebo, the trial cannot say how much of the effect belongs to thyme. EMA’s assessors read “acute bronchitis” in those trials as common cold with productive cough, which is the honest clinical frame.

Productive cough with a cold is the indication that matters. EMA: thyme herb preparations are traditional herbal medicinal products for productive cough associated with a cold, based on long-standing use. Its assessors were explicit that randomised, placebo-controlled trials of thyme as the only active ingredient are not published. The Knols 1994 thyme-syrup-versus-bromhexine study (60 patients, five days, no difference) was too small, had no placebo group, and used a poorly characterised syrup. The paediatric data are open, sponsor-run observational studies—one company report of 154 children aged two months to 14 years on thyme syrup, 93.5% of whom “improved” without any control group. EMA used those reports as documentation of safe use, not efficacy. That is the honest ceiling for thyme on its own.

The combination trials are where the numbers live. Kemmerich, Eberhardt, and Stammer (Arzneimittelforschung 2006) gave 361 adults with acute bronchitis a thyme-ivy syrup (Bronchipret Saft, 5.4 ml three times daily, n=182) or placebo (n=179) for 11 days. Daytime coughing fits fell 68.7% versus 47.6% by days 7–9, and a 50% reduction came about two days sooner. Kemmerich (2007) used thyme-primrose film-coated tablets (Bronchipret TP, one tablet three times daily, n=183 versus 178): 67.1% versus 51.3%. Gruenwald, Graubaum, and Busch (Arzneimittelforschung 2005) randomised 150 outpatients to thyme-primrose drops (Bronchicum Tropfen, 1 ml five times daily) or placebo for 7–9 days; 58.7% versus 5.3% were symptom-free at the end. Wagner, Cramer and colleagues (Forschende Komplementärmedizin 2015) pooled three of four ivy/primrose/thyme trials and found a risk ratio of 1.40 (95% CI 1.23–1.60) for cough response. These are product-specific trials of marketed brands. Placebo groups improved substantially too, as acute coughs do.

Gums and plaque are a thymol story, not a thyme-tea story. In a 2003 advance notice of proposed rulemaking, FDA published its Dental Plaque Subcommittee’s recommendation placing the fixed combination of eucalyptol 0.092%, menthol 0.042%, methyl salicylate 0.060%, and thymol 0.064% in Category I (safe and effective) for antigingivitis/antiplaque rinses. Araujo and colleagues (JADA 2015) meta-analysed 29 six-month trials, all sponsored by the manufacturer, and found that adding the rinse to brushing and flossing cut whole-mouth gingivitis by 16.0% and plaque by 27.7% compared with mechanical hygiene alone. That is the four-oil combination. EMA’s assessors note a thymol rinse that did no better than water on bleeding and plaque scores (Maruniak 1992) and a six-month four-oil toothpaste that did not beat its vehicle (Charles 2000).

Everything else is traditional or preclinical. Health Canada’s 2008 monograph lists traditional gargles for laryngitis and tonsillitis, topical use on minor wounds, and oral use for flatulent dyspepsia. Older sources add pertussis, stomatitis, and halitosis. Thyme oil is antibacterial and antifungal in dishes, and thymol has a long EPA history as an antimicrobial and fungicide ingredient. Thymol is also a working pesticide: Apiguard (25% thymol) and Api Life Var (74.09% thymol with eucalyptus oil and menthol) are EPA-registered against varroa mites in beehives. None of that is a human infection treatment. Thyme oil is not an antibiotic, not a cure for resistant bacteria, and not a reason to skip care for pneumonia, strep throat, or pertussis.

EMA thyme herb posology (traditional use; adolescents over 12, adults, and elderly): herbal tea, 1–2 g of comminuted herb in 150 ml boiling water as an infusion, three to four times daily; liquid extract (DER 1:1, ethanol 24%), 1–2 ml three to four times daily; tincture 1:5 (ethanol 70%), 2–6 ml three times daily, or tincture 1:10 at 40 drops three times daily; dry extract (DER 6–10:1, ethanol 70%), 75–200 mg three times daily. Only two preparations are allowed from age four: the German-pharmacopoeia liquid extract (DER 1:2–2.5), 0.5–0.9 ml three to five times daily, and the aqueous fresh-herb liquid extract often called expressed juice, 7–10 ml two to three times daily. Everything else is not recommended under 12. If symptoms last longer than a week, or breathlessness, fever, or purulent sputum appears, see a clinician.

EMA thyme oil posology (traditional use, 2020 revision): oral, adults only, 0.2–0.25 ml per dose three to five times daily (0.6–1.25 ml a day) as an expectorant in cough with a cold; not under 18. Cutaneous liquids or semi-solids up to 10%, applied to chest and back up to three times daily, adults only. Never on the face, and particularly not near the nose of babies and infants under two because of the risk of laryngospasm. Bath additive: 0.007–0.025 g per litre for adults and adolescents, lower amounts for children aged three to 12, not under three; bath at 35–38 °C for 10–20 minutes, daily or every second day. Those are licensed-product numbers. They are not a recipe for dripping retail essential oil into tea.

Combination products: EMA’s well-established adult posologies include a fixed combination of 160 mg dry thyme extract and 60 mg dry primula root extract three times daily (the Kemmerich 2007 tablet), 0.43 g liquid thyme extract with 0.21 g primula root tincture five times daily, and 0.5 g liquid thyme extract with 0.25 g liquid primula root extract six times daily. The well-established forms are not recommended under 18, and a week without improvement means a doctor or pharmacist. Other thyme–primula combinations sit on the traditional shelf, some from age four. Thyme-ivy syrups rest on the Kemmerich 2006 trial rather than on the thyme–primula monograph. Read which combination, which extract, and which age band is on the box.

Kitchen and shelf: thyme herb is a GRAS spice in the United States (21 CFR 182.10), and thyme oil and extract are GRAS as flavourings (21 CFR 182.20) at food-use levels. That is not a medicinal dose. Retail essential oils and supplement capsules are rarely labelled by chemotype, extract ratio, or thymol content. HerbalGram notes that commercial white thyme oil is redistilled from red. Undiluted oil is an irritant; EMA’s assessors cite skin irritation above about 8% in petrolatum. A warm infusion or a gargle is a reasonable traditional preparation. Swallowing essential oil is not a home remedy, and the bottle belongs out of children’s reach.