Mullein: The Lung Herb Nobody Has Tested
It is on almost every lung supplement in America. It has no human breathing trial. Both of those things are true at once.
Mullein leaf (Verbascum thapsus) has been used as a soothing expectorant for centuries and appears on most lung supplements sold in the United States. A 2022 review collected the folk record and the laboratory work and found no human trials of mullein for cough, asthma or lung function. It is traditional use, not proven benefit.
Why mullein is on every bottle
Pick up any lung supplement in a US health shop and there is a good chance mullein is on the label. Often it is first. It is the ingredient that makes a formula read as a breathing formula at a glance, in the way that melatonin makes something read as a sleep product.
The reason is history rather than data. Mullein is a tall biennial with soft grey-green leaves that grows on waste ground across Europe and North America, and it has been used for respiratory complaints for a very long time. The dried leaves were smoked, brewed and steeped. Nineteenth-century American eclectic physicians used it. It has the strongest folk credentials of any herb in this category.
Folk credentials are not nothing. A plant that stays in continuous use for centuries usually has some reason for it, and the traditional record is a reasonable place to look for candidates to test. The problem is what happened next, which is that nobody tested it.
What the research actually shows
The most useful single source is a 2022 review in Phytotherapy Research that collected everything published about Verbascum thapsus (Gupta et al., 2022). It is a thorough piece of work and it is worth reading what it found, and did not.
It found antibacterial activity in laboratory assays, including against some respiratory organisms in a dish. It found antioxidant and anti-inflammatory activity in cell models. It documented the traditional use as an expectorant and demulcent across several cultures. It found chemistry: iridoid glycosides, flavonoids, saponins and a substantial amount of mucilage.
What it did not find is a single human clinical trial of mullein for cough, for asthma, for bronchitis or for lung function. Not a small one. Not a pilot. Not an open-label study with twelve people in it.
What that does and does not mean
It does not mean mullein does nothing. Absence of evidence is not evidence of absence, and plenty of things that work were unproven for a long time before somebody funded a trial.
It does mean that anybody telling you mullein is clinically proven for breathing is either mistaken or selling something. And it means that when a supplement leads with mullein, the ingredient doing the most work on the packaging is doing the least work in the evidence base.
| Ingredient | Best available human evidence | Grade |
|---|---|---|
| Vitamin C | Cochrane review, 29 trials, 11,306 people | Strong, and the finding is negative for prevention |
| Bromelain | 116 children with acute sinusitis, cohort study | Moderate |
| Marshmallow root | 822 people, uncontrolled surveys | Moderate |
| Green tea | 13,570 adults, cross-sectional survey | Moderate, association only |
| Cordyceps | 28 adults, small RCT of a blend | Low to moderate |
| Ginger | Isolated airway tissue and mice | Preclinical |
| Mullein | None | Traditional use only |
The mechanism that probably is real
There is one part of the mullein story that holds up better than the rest, and it has nothing to do with the lungs.
Mullein leaf contains mucilage: long-chain polysaccharides that swell in water into a slippery gel. That is a physical property, measurable in a laboratory, and it is the same property that makes marshmallow root and slippery elm useful. A mucilaginous herb coats an irritated throat, and a coated throat hurts less and triggers fewer coughs.
This is worth separating out clearly. The demulcent effect is plausible, physical and fast. The expectorant claim, which is about loosening mucus deep in the airway, is the one with no human evidence. Those two claims get blurred together on packaging all the time, and they are not the same.
It also has a practical consequence for format. A physical coating effect needs physical contact. A capsule that dissolves in the stomach cannot coat a throat. A syrup, a lozenge or a spray can. If mullein is on the label of a capsule, the one part of its story that is probably real has been engineered out.
BreathiZen is the product this site sells
Ten named botanicals, one serving a day, 60-day money-back guarantee. We also publish, on every page, the fact that its ingredient amounts are not disclosed.
Mullein against the alternatives
If throat comfort in dry air or after a cold is what you actually want, there are ingredients with better evidence than mullein for precisely that.
- Marshmallow root has the same mucilage mechanism and at least has human survey data behind it: 822 people reported dry cough easing within about ten minutes (Fink et al., 2018).
- Honey is the unglamorous answer. It has more trial evidence for night-time cough in children than any herb in this category, and it costs almost nothing.
- Bromelain has the best human data of anything commonly found in these formulas, though it was studied in sinuses rather than lungs (Braun et al., 2005).
- NAC is the ingredient with the strongest position for mucus, and it is conspicuously missing from most multi-ingredient lung blends.
None of that means a formula containing mullein is a bad formula. It means mullein should not be the reason you choose it. Look at what else is in the bottle, and at whether the amounts are published.
What to do with this information
Do not pay a premium for mullein
It is cheap, it grows on waste ground, and it has no human evidence. If a product is priced on the strength of its mullein content, it is priced on a story.
Check what else is on the label
A formula with mullein plus bromelain, marshmallow root and a published amount of each is a reasonable product. Mullein alone at a high price is a folk remedy with a modern label.
Prefer a format that touches the throat
Sprays, syrups and lozenges let the one plausible mechanism work. Capsules do not.
Look for the amount
This applies to every ingredient, not just mullein. A label without amounts cannot be compared with anything.
Keep your expectations proportionate
Traditional use is a reason to try something cheap and low-risk. It is not a reason to expect a measurable change in how you breathe.
For what it is worth, the product this website sells leads with mullein, and everything above applies to it. Our own ingredients page grades mullein's evidence as weak and says so in a table on the home page. We would rather you bought it understanding that than bought it believing something untrue.
The BreathiZen ingredients, graded →The full category guide →
References
Every source linked here was opened and checked.
- Braun et al. — 2005. Therapeutic use, efficiency and safety of the proteolytic pineapple enzyme Bromelain-POS in children with acute sinusitis in Germany. In Vivo · PMID 15796206.
- Leelakanok et al. — 2023. Efficacy and safety of bromelain: A systematic review and meta-analysis. Nutrition and Health · PMID 37157782.
- Gupta et al. — 2022. Health-promoting and disease-mitigating potential of Verbascum thapsus L. (common mullein): A review. Phytotherapy Research · PMID 35088467.
- Fink et al. — 2018. Marshmallow Root Extract for the Treatment of Irritative Cough: Two Surveys on Users' View on Effectiveness and Tolerability. Complementary Medicine Research · PMID 30064132.
- Bonaterra et al. — 2020. Anti-inflammatory and Anti-oxidative Effects of Phytohustil and Root Extract of Althaea officinalis L. on Macrophages in vitro. Frontiers in Pharmacology · PMC7090173.
- Hirsch et al. — 2016. Cordyceps militaris Improves Tolerance to High-Intensity Exercise After Acute and Chronic Supplementation. Journal of Dietary Supplements · PMID 27408987.
- Oh et al. — 2018. Consuming Green Tea at Least Twice Each Day Is Associated with Reduced Odds of Chronic Obstructive Lung Disease in Middle-Aged and Older Korean Adults. The Journal of Nutrition · PMID 29378037.
- Townsend et al. — 2013. Effects of Ginger and Its Constituents on Airway Smooth Muscle Relaxation and Calcium Regulation. American Journal of Respiratory Cell and Molecular Biology · PMID 23065130.
- Evans et al. — 2021. A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of l-Theanine on Stress in a Healthy Adult Population. Neurology and Therapy · PMID 34562208.
- Hanus et al. — 2004. Double-blind, randomised, placebo-controlled study of a fixed combination containing Crataegus oxyacantha and Eschscholtzia californica with magnesium in mild-to-moderate anxiety disorders. Current Medical Research and Opinion · PMID 14741074.
- Zhang et al. — 2014. A Novel Analgesic Isolated from a Traditional Chinese Medicine. Current Biology · PMID 24388848.
- Hemilä et al. — 2013. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews · PMID 23440782.
- U.S. Food and Drug Administration. Is It Really 'FDA Approved'?. FDA.gov.
- U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. FDA.gov.
- Electronic Code of Federal Regulations. 21 CFR Part 111: Current Good Manufacturing Practice for Dietary Supplements. eCFR.gov.
- NCCIH (National Institutes of Health). Know the Science: How Medications and Supplements Can Interact. NCCIH.nih.gov.