Related Terms

• Bazoton®, big string nettle, Brennessel (German), bull nettle, chichicaste, common nettle, dog nettle, extract of Radicis Urticae (ERU), Fragdor®, garden nettle, gerrais, grand ortie (French), grande ortie, great stinging nettle, great nettle, greater nettle, gross d'ortie, Hostid®, isirgan, kazink, Kleer®, nabat al nar, nessel (German), nettle, nettles, ortic (Italian), ortie, ortiga (Spanish), pokrywa grosse brenessel, Prostaforton®, Prostagalen®, racine d'ortie small nettle (Urtica urens), stingers, urtica, Urtica dioica, Urtica dioica agglutinin (UDA), Urtica herba/folium (dried leaves or aerial parts of U. dioica and U. urens), Urtica major, Urtica radix (root), Urticaceae, urtiga, zwyczajna (Polish).

Background

• The genus name Urtica comes from the Latin verb urere meaning, "to burn," because of its urticate (stinging) hairs that cover the stem and underside of the leaves. The species name dioica means "two houses" because the plant usually has male or female flowers.

• The most common uses for stinging nettle are treatment of benign prostatic hyperplasia (BPH, enlarged prostate), arthritis, allergies and pain, cough, tuberculosis, as an astringent and expectorant, urinary tract disorders, and externally as a hair and scalp remedy for oily hair and dandruff. It is also frequently used as a diuretic to increase the flow of urine. There are some data supporting the use of nettle in the treatment of symptoms of BPH, but solid clinical data are lacking for other indications.

• Nettle is generally regarded as safe because the plant is also used as a green, leafy vegetable. Other than urticaria ("hives") from contacting the stinging hairs, gastrointestinal discomfort is the only reported adverse effect.

Scientific Evidence

Tradition/Theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious and should be evaluated by a qualified health care professional.

• Abortion, aging, allergies, alopecia (hair loss), anaphylactic shock, anemia, angina pectoris (chest pain), animal bites, anthelmintic (expels worms), antidote to poisons (hemlock and henbane), antifungal, antihypertensive (blood pressure lowering), anti-inflammatory, antiviral, aphrodisiac, asthma, astringent, biliary colic, bladder disturbances, bleeding, blood purification, breast milk stimulation, bruises, burns, cancer, cardiac abnormalities, chicken pox, childbirth facilitation/induction, cholera, colitis (inflammation of the colon), coma, cough, cutaneous (skin) disorders, dandruff, diabetes, diarrhea, diuretic, dysentery (severe diarrhea), eczema, edema (swelling), exhaustion, expectorant, food uses, gangrene, gastric secretory inhibition, goiter (enlarged thyroid), gout (inflammation of the foot), hair tonic, hemorrhage, hemorrhoids, herpes (STD), immunostimulation, insect repellant, iron deficiency, kidney disorders, kidney or bladder stones, labor induction, laxative, menorrhagia (excessive menstruation), mouth sores, muscle aches, nasal polyposis (growths), nephritis (inflammation of the kidney), neuralgia (nerve pain), nosebleeds, paralysis, parasitic worm infections, poor circulation, pregnancy problems, promotion of menstruation, pulmonary conditions, rash, renal impairment, rheumatism, scabies, sciatica (leg pain), scurvy, seborrhea (inflammation near the oil glands), shivering, shortness of breath, skin eruptions, snakebites, sore throat, spleen disorders, splenomegaly (enlarged spleen), sprains, stiff joints, stings (scorpion), stomachache, swelling, systemic lupus erythematosus (autoimmune disease when the body's immune system attacks cells and tissue), tendonitis (inflamed tendon), tonic, tuberculosis, typhus (disease transmitted by lice or fleas), urinary tract infection (UTI), uterine bleeding (after childbirth), venous disorders, wheezing, wound healing.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older):

• Various doses of nettle have been used in clinical trials; however, none have been proven effective. For benign prostatic hyperplasia (enlarged prostate), 1-2 capsules of Bazoton® containing 300 milligrams extract of Radix urticae; ERU) has been taken twice daily for up to six months. Bazoton® Liquidum has also been studied in doses of 3 milliliters twice daily for three months. For allergic rhinitis, 600 milligrams freeze dried nettle at the onset of symptoms for one week has been used. As an extract, nettle has traditionally been given in doses of 30-150 drops daily for six months.

Children (younger than 18 years):

• There is no proven safe or effective dose for nettle in children.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

• Avoid in individuals with a known allergy or hypersensitivity to nettle, the Urticaceae family or any constituent of nettle products. Two patients taking a freeze-dried preparation of Urtica dioica for the treatment of allergic rhinitis had intensification of allergy symptoms.

Side Effects and Warnings

• Nettle therapy was generally well-tolerated for up to two years in available human trials. However, contact with the hairs of the nettle plant may cause short-lived whealing ("hives"), burning, itching, localized rash and a prolonged tingling sensation. Other reported side effects include continual pain in the gastrointestinal tract, hyperperistalsis (excessive rapidity of the passage of food through the stomach and intestine), and mild gastric discomfort when the medication was taken on an empty stomach. Patients taking Bazoton® capsules have experienced side effects such as constipation, diarrhea and gastric disorder.

• The nettle plant contains a substance that is a coumarin derivative. Nettle may increase the risk of bleeding. Caution is advised in patients with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.

• Although not well studied in humans, nettle may increase blood glucose, but not likely enough to be of clinical concern. Nonetheless, use cautiously in patients with diabetes mellitus due to potential increased glycemia. Monitor blood glucose levels.

• Although not well studied in humans, nettle may cause diuresis (water loss, excessive urination), uterine contractions, or low blood pressure. Use with caution in patients with hyponatremia (low sodium levels in the blood) as nettle has a synergistic diuretic effect. Monitor sodium levels.

• Elderly persons should use nettle cautiously for a possible hypotensive (decreased blood pressure) crisis that might be affected by nettle. Nettle should not be administered to children as it has not been studied.

Pregnancy and Breastfeeding

• Nettle is not recommended in pregnant or breastfeeding women due to a lack of available scientific evidence. In theory, nettle may induce uterine stimulation.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

• Alpha blockers are typically given to treat high blood pressure (hypertension) and to treat benign prostatic hyperplasia (enlarged prostate). Co-administration of nettle and alpha blockers may theoretically have an additive blood pressure lowering effect. Caution is advised.

• Administration of nettle may also theoretically have an additive effect with antihypertensive (blood pressure lowering) agents.

• Nettle root contains a coumarin constituent and nettle leaves contain vitamin K. Thus, nettle may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

• Nettle leaves have been used with diclofenac in the treatment of acute arthritis.

• Although not well studied in humans, administration of nettle may theoretically have an additive effect on diuretics, resulting in dehydration and abnormally low potassium concentrations in the blood (hypokalemia).

• Finasteride, a 5 α-reductase inhibitor, is used in the treatment of benign prostatic hyperplasia. Co-administration of finasteride and nettle may have additive effects. Caution is advised.

• Although not well studied in humans, nettle may increase blood sugar levels. Caution is advised when using medications that may alter blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

Interactions with Herbs and Dietary Supplements

• Theoretically, nettle may cause diuresis (increase in the flow of urine). Caution is advised when taking with other herbs that have a similar effect.

• Although not well studied in humans, niacin may increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, such as kava, dong quai, horse chestnut and niacin, although this has not been proven in most cases. Nettle leaves may also theoretically have an additive effect with other anti-inflammatory agents.

• Theoretically, nettle may increase blood glucose levels. Caution is advised when using herbs or supplements that may alter blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment. Theoretically, nettle may lower blood pressure levels.

• Saw palmetto and pygeum are used to treat benign prostatic hyperplasia (enlarged prostate) and may have additive therapeutic effects with nettle.

• Soy isoflavones appear to inhibit type II 5 α-reductase and may have additive effects with nettle.

Author Information

• This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

1. Dantas SM. Menopausal symptoms and alternative medicine. Prim Care Update Ob/Gyns 1999;6:212-220.

2. Dathe G, Schmid H. [Phytotherapy of the benign prostatic hyperplasia (BPH). Double-blind study with an extract of Radicus Urticae (ERU)]. Urologe B 1987;27:223-226.

3. Hill N, Stam C, van Haselen RA. The efficacy of Prrrikweg gel in the treatment of insect bites: a double-blind, placebo-controlled clinical trial. Pharm World Sci 1996;18(1):35-41. View Abstract

4. Koch E. Extracts from Fruits of Saw Palmetto (Sabal serrulata) and Roots of Stinging Nettle (Urtica dioica): Viable Alternatives in the Medical Treatment of Benign Prostatic Hyperplasia and Associated Lower Urinary Tracts Symptoms. Planta Med 2001;67(6):489-500. View Abstract

5. Konrad L, Muller HH, Lenz C, et al. Antiproliferative effect on human prostate cancer cells by a stinging nettle root (Urtica dioica) extract. Planta Med 2000;66(1):44-47. View Abstract

6. Krzeski T, Kazon M, Borkowski A, et al. Combined extracts of Urtica dioica and Pygeum africanum in the treatment of benign prostatic hyperplasia: double-blind comparison of two doses. Clin Ther 1993;15(6):1011-1020. View Abstract

7. Lopatkin N, Sivkov A, Walther C, et al. Long-term efficacy and safety of a combination of sabal and urtica extract for lower urinary tract symptoms--a placebo-controlled, double-blind, multicenter trial. World J Urol 2005;23(2):139-146. View Abstract

8. Mittman P. Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis. Planta Med 1990;56(1):44-47. View Abstract

9. Randall C, Randall H, Dobbs F, et al. Randomized controlled trial of nettle sting for treatment of base-of-thumb pain. J R Soc Med 2000;93(6):305-309. View Abstract

10. Schneider T, Rubben H. [Stinging nettle root extract (Bazoton-uno) in long term treatment of benign prostatic syndrome (BPS). Results of a randomized, double-blind, placebo controlled multicenter study after 12 months]. Urologe A 2004;43(3):302-306. View Abstract

11. Sokeland J, Albrecht J. [Combination of Sabal and Urtica extract vs. finasteride in benign prostatic hyperplasia (Aiken stages I to II). Comparison of therapeutic effectiveness in a one year double-blind study]. Urologe [A] 1997;36(4):327-333. View Abstract

12. Sokeland J. Combined sabal and urtica extract compared with finasteride in men with benign prostatic hyperplasia: analysis of prostate volume and therapeutic outcome. BJU Int 2000;86(4):439-442. View Abstract

13. Tahri A, Yamani S, Legssyer A, et al. Acute diuretic, natriuretic and hypotensive effects of a continuous perfusion of aqueous extract of Urtica dioica in the rat. J Ethnopharmacol 2000;73(1-2):95-100. View Abstract

14. Taskila K, Saarinen JV, Harvima IT, et al. Histamine and LTC4 in stinging nettle-induced urticaria. Allergy 2000;55(7):680-681. View Abstract

15. Vontobel HP, Herzog R, Rutishauser G, et al. [Results of a double-blind study on the effectiveness of ERU (extractum radicis Urticae) capsules in conservative treatment of benign prostatic hyperplasia]. Urologe A 1985;24(1):49-51. View Abstract