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Nettle

Common name: Stinging nettle

Botanical name: Urtica dioica

Photo

© Steven Foster

Parts used and where grown

Nettle is a leafy plant that is found in most temperate regions of the world. The Latin root of Urtica is uro, meaning “I burn,” indicative of the small stings caused by the little hairs on the leaves of this plant that burn when contact is made with the skin. The root and leaves of nettle are used in herbal medicine.

Nettle has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings Health Concerns
3Stars

Benign prostatic hyperplasia (root extract)

2Stars

Osteoarthritis

1Star

Hay fever

Pregnancy and postpartum support

Rheumatoid arthritis

Urinary tract infection

3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies)

Nettle has a long history of use. The tough fibers from the stem have been used to make cloth and cooked nettle leaves were eaten as vegetables. From ancient Greece to the present, nettle has been documented for its traditional use in treating coughs, tuberculosis, and arthritis and in stimulating hair growth.

Active constituents

There has been a great deal of controversy regarding the identity of nettle’s active constituents. Currently, it is thought that polysaccharides (complex sugars) and lectins are probably the active constituents. Test tube studies suggest the leaf has anti-inflammatory actions. This is thought to be caused by nettle preventing the body from making inflammatory chemicals known as prostaglandins.1 Nettle’s root affects hormones and proteins that carry sex hormones (such as testosterone or estrogen) in the human body. This may explain why it helps benign prostatic hyperplasia (BPH).2 Although less frequently used alone like saw palmetto or pygeum, some limited clinical trials suggest benefit of nettle root extract for men with milder forms of BPH.3

A preliminary trial reported that capsules made from freeze-dried leaves reduced sneezing and itching in people with hay fever.4 Further studies are needed to confirm this finding, however.

The historical practice of intentionally applying nettle topically with the intent of causing stings to relieve arthritis has been assessed by a questionnaire in modern times.5 The results found intentional nettle stings safe, except for a sometimes painful, sometimes numb rash that lasts 6–24 hours. Additional trials are required to determine if this practice is therapeutically effective.

How much is usually taken?

During the allergy season, two to three 300 mg nettle leaf capsules or tablets or 2–4 ml tincture can be taken three times per day. For BPH, 120 mg of a concentrated root extract in capsules can be taken two times per day.6 Many products for BPH will combine nettle root with saw palmetto or pygeum extracts. Intentional stinging with nettles should only be undertaken after consultation with a physician knowledgeable in botanical medicine.

Are there any side effects or interactions?

Nettle may cause mild gastrointestinal upset in some people. Although allergic reactions to nettle are rare, when contact is made with the skin, fresh nettle can cause a rash secondary to the noted stings.7 Nettle leaf is considered safe for use in pregnancy and breast-feeding.

Are there any drug interactions?
Certain medicines may interact with nettle. Refer to drug interactions for a list of those medicines.

References:

1. Obertreis B, Giller K, Teucher T, et al. Antiphlogistic effects of Urtica dioica folia extract in comparison to caffeic malic acid. Arzneimittelforschung 1996;46:52–6.

2. Hirano T, Homma M, Oka K. Effects of stinging nettle root extracts and their steroidal components on the Na+,K+-ATPase of the benign prostatic hyperplasia. Planta Med 1994;60:30–3.

3. Vontobel H, Herzog R, Rutishauser G, Kres H. Results of a double-blind study on the effectiveness of ERU (extractum radicis urticae) capsules in conservative treatment of benign prostatic hyperplasia. Urologe 1985;24:49–51 [in German].

4. Mittman P. Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis.Planta Med 1990;56:44–7.

5. Randall C, Meethan K, Randall H, Dobbs F. Nettle sting of Urtica dioica for joint pain--an exploratory study of this complementary therapy. Compl Ther Med 1999;7:126–31.

6. Brown D, Austin S, Reichert R. Benign Prostatic Hyperplasia and Prostate Cancer Prevention. Seattle: NPRC, 1997, 9–10.

7. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 216–7.

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