Benefits
Traditional expectorant and throat soother in herbal medicine
Health Canada lets licensed lungwort leaf products say they are traditionally used in herbal medicine as an expectorant to ease mucus buildup in the upper respiratory tract and as a demulcent to relieve a sore throat. Those claims rest on herbal reference books, not trials. The EU has no herbal monograph, and lungwort is not on the European Medicines Agency's list of herbs proposed for assessment.
Mucilage described as the basis of its soothing use
Herbal texts describe lungwort leaves as rich in mucilage, the slippery plant gel usually credited for demulcent herbs, and reviews list silicic acid among its constituents. No published measurement of the leaf's mucilage content, and no test of whether lungwort tea coats the throat in people, was found, so this rationale is traditional.
Rosmarinic acid and related caffeic acid compounds in the leaf
Chemical work on the aerial parts identified 45 phenolic compounds, 9 of them new to science, with rosmarinic acid the most abundant in both spring and autumn harvests. In phenolic-rich fractions, phenolic acids made up over 80 percent and flavonols about 5 percent. These figures describe the plant, not what reaches the body after drinking the tea.
Antioxidant and COX-2 enzyme activity in laboratory tests
In human blood plasma exposed to the oxidant peroxynitrite, lungwort extract at 1 to 100 micrograms per mL partly reduced damage to plasma components, and its compound yunnaneic acid B did the same. The extract also inhibited the inflammatory enzyme COX-2 in a test tube. No study has looked for these effects after people drink lungwort.
Effects on Staphylococcus aureus virulence in lab cultures
Against S. aureus strains from cystic fibrosis patients, a phenolic-rich lungwort extract barely slowed growth but usually reduced bacterial adhesion and alpha-toxin release. In some strains it instead favored biofilm, and it did not stop bacteria sticking to lung cells. The authors saw no role for it as a treatment or supportive agent.
Glucose transporter signals in cell and hen's egg screening
In a screen of 772 plant extracts, lungwort leaf and blossom extracts moved the glucose transporter GLUT4 to the cell surface in cultured cells, and a lungwort extract significantly lowered blood glucose in a hen's egg model after 60 minutes. No human or mammal feeding study has followed up.
Mechanism of action
Caffeic acid conjugates as radical scavengers
Yunnaneic acid B, first reported in the borage family from lungwort, scavenged DPPH radicals and peroxynitrite in chemical tests (EC50 7.14 and 50.45 micrograms per mL) and was not toxic to blood immune cells up to 50 micrograms per mL. Whether these compounds survive digestion and reach tissues in people is unknown.
Pyrrolizidine alkaloids need liver activation to become toxic
Borage-family plants make lycopsamine-type pyrrolizidine alkaloids, stored largely as N-oxides. According to the European Medicines Agency, after swallowing the N-oxides are reduced to free alkaloids, which liver CYP3A enzymes turn into reactive pyrroles that bind DNA and proteins; repeated low intakes may build up liver damage.
Anticoagulant glycopeptide in an injected extract
A Russian animal study isolated an anticoagulant glycopeptide from an ammonia extract of lungwort. Given into a vein, doses that cut overall clotting activity four to five fold kept it low for up to 6 hours. Whether drinking the tea affects blood clotting has never been tested.
Clinical trials
Laboratory LC-MS/MS analysis of 68 unsaturated pyrrolizidine alkaloids in infusions of 21 types of commercial tea (147 samples in all) from China and EU countries, with a margin of exposure risk assessment. The lungwort tea was sampled in the Netherlands in 2020. (Chen et al. 2022, Foods)
Commercial dried tea, brewed as 2 g in 150 mL of boiling water for 10 minutes; no human participants.
Lungwort tea held 8 pyrrolizidine alkaloids, mainly intermedine N-oxide, lycopsamine N-oxide and intermedine, at a mean 1,769.7 micrograms per kg of dry tea (range 996.5 to 2,753.2). One 2 g cup a day would supply about 3.5 micrograms, above the 0.1 microgram a day lifetime limit used in Germany and the Netherlands, and the margin of exposure for lifelong daily use fell below 10,000, the usual threshold for concern. Weighting each alkaloid by interim relative potency factors cut the total to 37.8 micrograms per kg and removed the concern; those factors are provisional.
In vitro study of a phenolic-rich Pulmonaria officinalis extract against Staphylococcus aureus clinical isolates, prompted by use of lungwort supplements among people with cystic fibrosis. No human participants. (Sadowska et al. 2019, Molecules)
S. aureus strains isolated from cystic fibrosis patients, plus human A549 lung epithelial cells for adhesion and toxicity tests.
The extract was only weakly bacteriostatic (MIC 1 to 2 mg per mL). At lower concentrations it usually reduced bacterial adhesion, lowered sortase A activity and alpha-toxin output, and slightly reduced protein A. In some strains it favored biofilm, and it did not reduce adhesion to lung cells. It was not toxic to lung cells up to 4 mg per mL. The authors saw no role for it as a therapeutic or supportive agent, suggesting at most a prophylactic role that would first need in vivo testing.
In vitro and in silico comparison of phenolic-rich fractions from the aerial parts of Pulmonaria officinalis and Pulmonaria obscura. No human participants. (Krzyżanowska-Kowalczyk et al. 2021, Molecules)
Human blood plasma, platelets and peripheral blood mononuclear cells treated in the lab; COX-2 enzyme assays.
Phenolic acids made up over 80 percent of the fractions, led by caffeic acid conjugates such as rosmarinic, lithospermic and salvianolic acids. At 1 to 100 micrograms per mL the extracts partly prevented peroxynitrite damage to plasma and did not harm platelets or immune cells. P. officinalis inhibited COX-2 more strongly than P. obscura (IC50 13.28 and 7.24 micrograms per mL in two assays). Docking named ten compounds that may bind COX-2.
In vitro study of a 70% ethanol extract of Pulmonaria officinalis: chemical profiling, antioxidant assays, and comet assay tests of DNA damage and protection in normal fetal fibroblast cells (MRC-5). No human participants. (Ignjatijević et al. 2025, Pharmaceutics)
MRC-5 normal fetal fibroblast cells in culture.
The extract was rich in polyphenols; GC-MS found phytol as the most abundant compound, with terpenoids, fatty acids and alkaloids also present. At higher concentrations it damaged DNA. At non-genotoxic concentrations (3.9 to 15.6 micrograms per mL), pretreatment reduced hydrogen peroxide DNA damage, by up to 28 percent at the lowest concentration. A cell culture result that says nothing directly about tea in people.