Educational information, not medical advice — ask your doctor or midwife.
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Sundew is a cough herb. It is a small carnivorous bog plant whose leaves are covered in sticky red hairs that trap insects. Herbalists dry the whole flowering plant and use it for dry, tickly, barking coughs.
The plant grows in peat bogs across Europe, Asia and North America. Wild round-leaved sundew is now protected in many countries. Most material sold today comes from farmed plants or from related Drosera species grown abroad.
American Eclectic doctors in the 1800s used it for spasmodic coughs, and European herbalists did the same. It still turns up in cough syrups, drops and tinctures sold in Europe.
The honest verdict on evidence: thin. Nearly every trial used sundew mixed with other herbs, so its own effect is unclear. A long record of traditional use is not proof that a remedy works, and it is not proof that it is safe.
No one has shown how sundew works in people. The main idea is that it quiets the cough reflex and eases tightness in the airways.
In animal and isolated-tissue studies, naphthoquinones such as plumbagin appear to relax airway muscle. In test tubes, the same compounds slow some bacteria and lower markers of inflammation. Whether any of that happens in a human throat, at the small amounts in a syrup, is not established.
The plant also holds mucilage, a slippery gel-like fibre. Mucilage may coat and soothe a raw throat as you swallow it. That is a plausible local effect, not a proven one.
Flavonoids in the plant act as antioxidants in lab work. Antioxidant activity in a dish does not predict relief from a cough.
Sundew is sold in several forms:
- Cough syrups and drops, usually with other herbs such as thyme, ivy or plantain.
- Liquid tincture in alcohol, sometimes as drops in water.
- Dried herb for tea, though this is less common.
- Homeopathic Drosera, which is diluted so far that little or no plant material remains. That is a different product from the herbal extract, even though the name looks the same.
- Capsules and lozenges, mostly in blends.
Labels in Europe may carry a traditional herbal registration mark. That mark means the product is made to a quality standard and has a long history of use. It does not mean the remedy was proven to work in trials.
Sundew has a long folk record as a cough plant. Eclectic physicians in 19th-century America listed it for whooping cough, dry spasmodic cough and hoarseness. European herbals used it the same way, often as a syrup for children.
Older names hint at other claims. "Youthwort" and "lustwort" came from the belief that the dewy leaves preserved youth or stirred desire. Some writers also used the juice on warts and corns.
It entered formal pharmacy too. Sundew appeared in European pharmacopoeias and in homeopathic practice, where Drosera was a standard cough remedy. None of this history is described here as a reason to treat yourself.
Stop and see a doctor if any of these happen:
- Your cough lasts more than three weeks, or keeps coming back.
- You cough up blood, or thick green or brown phlegm.
- You have a fever, night sweats or losing weight without trying.
- You are short of breath, wheezing, or your chest hurts.
- You get a rash, itching or stomach pain after taking it.
Call emergency services for swelling of the lips, tongue or throat, or for sudden trouble breathing. That can be a severe allergic reaction.
In the UK and much of the EU, sundew is sold as a traditional herbal medicine or as an ingredient in registered cough products. In the United States it is sold as a dietary supplement, and it is not approved by the FDA to treat any illness. Round-leaved sundew is a protected wild species in several countries, so picking it can be illegal.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Sundew is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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