Benefits
Fewer daytime coughing fits with thyme-ivy and thyme-primrose blends
In two placebo-controlled trials of 361 adults each with acute bronchitis and a productive cough, 11 days of a thyme-ivy syrup or a thyme-primrose tablet cut daytime coughing fits by about two thirds vs about half on placebo, and a 50% drop came about 2 days sooner. Both were fixed two-herb products, so the effect cannot be credited to thyme alone.
Bronchial symptom scores with thyme-primrose drops
In a placebo-controlled trial of 150 adults with acute bronchitis that began under 48 hours earlier, drops of thyme extract with primrose root for 7 to 9 days lowered a bronchial symptom score from 12.0 to 1.0, vs 11.7 to 6.5 on placebo, and 58.7% vs 5.3% were symptom free at the end. This was a two-herb blend.
Activity-related cough in children given thyme syrup alone
In a triple-blind trial of 60 children aged 5 to 12 during a flare of asthma, powdered thyme as a syrup for a week, added to routine care, reduced cough brought on by activity more than placebo syrup, and one lung function measure (FEV1) differed. Wheezing, breathlessness and other lung function measures did not differ.
Thymol from thyme reaches the blood as thymol sulfate
In 12 healthy adults given one thyme-primrose tablet, free thymol was not found in blood, but its sulfate form peaked about 2 hours later, had a half-life of about 10 hours and was still detectable up to 41 hours. About 16% of the dose appeared in urine within 24 hours.
Antimicrobial activity of thymol and carvacrol in lab studies
Thyme essential oil inhibits many bacteria, fungi and yeasts in lab tests, including methicillin-resistant Staphylococcus aureus, with the action mainly attributed to thymol and carvacrol. EU assessors note that data on how much oil reaches the body after oral use are limited, so the meaning of these findings for people cannot be estimated.
Mechanism of action
Membrane damage in microbes (thymol and carvacrol)
The antibacterial and antifungal action of thyme oil is attributed mainly to its phenols thymol and carvacrol. Links between thymol concentration and killing of oral bacteria suggest that forming holes in the cell membrane is the main mode of action, and the oil's components act in an additive way.
Ciliary transport in the airways (animal and lab data)
Expectorant effects of thyme have long been recognized from experience. In rats given thyme extracts by mouth, an extract with a normal thymol content was more effective in ciliary transport tests than a low-thymol extract, and one extract acted on beta2 receptors in lab tests. EU assessors judged the doses too high to explain effects in people.
Airway smooth muscle relaxation
Thyme extracts relaxed precontracted guinea pig and rat trachea in organ bath studies. Thymol and carvacrol were active, but extracts nearly free of thymol also worked, and in one study the flavone luteolin was the main contributor, so several constituents appear to share the effect.
Inflammation signals in lab and small human studies
Thyme oil inhibits prostaglandin production and thymol reduced neutrophil elastase release in lab tests. In a small open-label study of adults with mild COVID-19, a thyme-ivy syrup was followed by numerically larger falls in IL-6 and IL-10 than no treatment, with uneven groups at baseline.
Antioxidant compounds
Rosmarinic acid, luteolin, thymol and carvacrol from thyme leaves scavenge free radicals in lab assays. The activity of extracts tracks their rosmarinic acid content, and that of the oil its phenol content. In one comparison, thyme tea scavenged fewer radicals than green or peppermint tea but more than olive or sage leaf.
Clinical trials
Double-blind, placebo-controlled, multicenter Phase IV trial of a fixed thyme-ivy fluid extract syrup (Bronchipret Saft), 5.4 mL three times daily for 11 days; primary outcome was the change in daytime coughing fits on days 7 to 9, counted by the patient. The abstract does not state funding (Kemmerich et al. 2006, Arzneimittelforschung)
361 adult outpatients with acute bronchitis, at least 10 coughing fits a day and a productive cough that began no more than 2 days before entry (182 syrup, 179 placebo).
Coughing fits on days 7 to 9 fell 68.7% on the blend vs 47.6% on placebo (p < 0.0001), and a 50% drop came 2 days sooner. Symptom score responder rates were 83.0% vs 53.9% at day 4 and 96.2% vs 74.7% at day 10 (p < 0.0001). Adverse events did not differ and none were serious. This was a two-herb product.
Double-blind, placebo-controlled, multicenter Phase IV trial of a fixed tablet of thyme herb and primrose root dry extracts (Bronchipret TP), 1 tablet three times daily for 11 days; same design and primary outcome as the thyme-ivy trial. The abstract does not state funding (Kemmerich 2007, Arzneimittelforschung)
361 adult outpatients with acute bronchitis, at least 10 coughing fits a day and a productive cough that began no more than 2 days before entry (183 tablet, 178 placebo).
Coughing fits on days 7 to 9 fell 67.1% on the blend vs 51.3% on placebo (p < 0.0001), and a 50% drop came about 2 days sooner. Symptom score responder rates were 77.5% vs 60.1% at day 4 (p = 0.0006) and 92.9% vs 75.8% at day 10 (p < 0.0001). Adverse events did not differ and none were serious. This was a two-herb product.
Double-blind, randomized, placebo-controlled, multicenter trial of drops of thyme fluid extract plus primrose root tincture (Bronchicum Tropfen), 1 mL five times daily for 7 to 9 days; primary outcome was the change in Bronchitis Severity Score (Gruenwald et al. 2005, Arzneimittelforschung)
150 adult outpatients with untreated acute bronchitis of under 48 hours (75 per group).
The symptom score fell from 12.0 to 1.0 on the blend vs 11.7 to 6.5 on placebo, a 5.8 point difference (p ≤ 0.001), and 58.7% vs 5.3% were symptom free at the end. Two adverse events occurred on the blend and five on placebo, none serious. This was a two-herb product.
Randomized, triple-blind, placebo-controlled trial of powdered Thymus vulgaris prepared as syrup, 20 mg/kg every 8 hours for one week, on top of routine medical treatment (Eskandarpour et al. 2024, Allergol Immunopathol (Madr))
60 children aged 5 to 12 with a mild to moderate asthma exacerbation (30 per group).
Activity-induced cough fell more with thyme than with placebo (p = 0.042), and FEV1 differed between groups (p = 0.048). Wheezing, breathlessness, FEV1/FVC, peak flow and FEF25-75% did not differ significantly. A single small trial.
Open-label, randomized, multicenter three-arm trial in adults with acute bronchitis comparing ivy extract EA 575 drops (Prospan) with ivy/thyme drops (Bronchipret) and thyme/primrose drops (Bronchicum), each taken per label; outcome was the change in Bronchitis Severity Score to day 7. Funded by Engelhard Arzneimittel, maker of the ivy product, and three authors are its employees (Kardos et al. 2025, Pharmaceuticals (Basel))
325 evaluated adults.
Ivy alone was non-inferior to both blends (both p < 0.0001). It was superior to the ivy/thyme blend (p < 0.0001) and missed significance for superiority over the thyme/primrose blend (reported as p < 0.0607). Adverse events were few, non-serious and similar across groups. Adding thyme to ivy showed no extra benefit here.