Knotweed is an herb. The whole flowering plant is used to make medicine.

Knotweed is used for swelling (inflammation) of the main airways in the lung (bronchitis), cough, sore throat, a mild form of gum disease (gingivitis), and other conditions, but there is no good scientific evidence to support these uses.
When taken by mouth: Knotweed is POSSIBLY SAFE when taken by mouth short-term. Three to four cups of tea per day, each prepared with 1.5 grams of knotweed powder, have been used with apparent safety.

When applied to the skin: Knotweed is POSSIBLY SAFE when used in a mouthwash twice daily for up to 2 weeks.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if knotweed is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.


NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
Insufficient evidence Effectiveness definitions
  • A mild form of gum disease (gingivitis). Early research suggests that a root extract of knotweed might be useful as a mouth rinse to treat gingivitis, decreasing bleeding and swelling of the gums.
  • Swelling (inflammation) of the main airways in the lung (bronchitis).
  • Cough.
  • Skin irritation.
  • Sore throat.
  • Stopping bleeding.
  • Tuberculosis.
  • Other conditions.
More evidence is needed to rate the effectiveness of knotweed for these uses.

Dosing & administration

The appropriate dose of knotweed depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for knotweed. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

Interactions with pharmaceuticals

It is not known if Knotweed interacts with any medicines. Before taking Knotweed, talk with your healthcare professional if you take any medications.

Interactions with herbs & supplements

There are no known interactions with herbs and supplements.

Interactions with foods

There are no known interactions with foods.


Knotweed might be able to reduce the swelling and bleeding that occur with gum disease.
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This monograph was last reviewed on 17/10/2023 11:00:00 and last updated on 23/01/2013 17:31:44. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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