Dwarf Nettle (Urtica urens L.): A Comprehensive Reference
1. Identity, Taxonomy, and Nomenclature
Urtica urens L., commonly known as annual nettle, dwarf nettle, small nettle, dog nettle, burning nettle, or bush nettle, is a herbaceous annual flowering plant species in the nettle family Urticaceae. The terms "dwarf nettle" and "small nettle" refer principally to its comparatively modest stature relative to the more widely studied common or stinging nettle (Urtica dioica L.).
The genus name Urtica comes from the Latin word urere, meaning "to burn," which aptly refers to the intense stinging sensation one can experience from coming into contact with the plant's hairs. The species epithet urens further emphasizes this burning characteristic, as it also translates to "burning" in Latin. By extension, the English word "urticaria" means any itching similar to that caused by nettle stings.
Urtica urens is an annual plant, monoecious (with male and female flowers on the same plant) and generally much shorter than U. dioica. It can be distinguished from the perennial and dioecious U. dioica by its more rounded leaves with coarser, deeper toothing, and with the terminal tooth of similar length to the adjacent teeth. It is reputed to sting more strongly than Urtica dioica.
U. urens is an herbaceous annual plant that typically reaches heights of 30–80 cm. It is characterized by small, ovate leaves which can measure up to 6 cm in length. The leaves are typically serrated and have a soft green appearance. The plant tends to display a branching structure with slender stems covered in fine hairs that deliver its notorious sting when touched. Flowers are small, inconspicuous, and can be greenish or yellowish, appearing in clusters.
The species is native to Eurasia, including the Himalayan regions of Kalimpong, Darjeeling, and Sikkim in India, and can be found in North America, New Zealand, and South Africa as an introduced species. It is also widely distributed across South America (Argentina, Brazil, Bolivia, Chile, and Uruguay), Africa, Australia, Europe, and Asia.
Both Urtica dioica and Urtica urens are the species of the genus known to possess medicinal properties. Within official European regulatory and pharmacopoeial frameworks, the two species are frequently assessed together and are considered therapeutically interchangeable for the leaf (folium) preparation.
Common Preparations and Dosage Forms
Nettle leaf consists of the whole or cut, dried leaves of Urtica dioica L., Urtica urens L., their hybrids, or their mixtures; and is available as a comminuted herbal substance for tea. Beyond the dried leaf for infusion, the plant is also prepared as:
- Herbal infusion (tea): The most traditional and widely used form, prepared by pouring boiling water over dried leaves. The standard preparation described in official literature involves pouring one cup of boiling water over 2–4 teaspoonfuls (approximately 2–4 g) of nettle leaves.
- Dry extract: A dose of 536 mg dry extract from Urticae folium (drug-to-extract ratio 8–10:1, extraction solvent ethanol 50% v/v) as a single dose, taken up to twice daily (equivalent to 2 × 4.8 g of herbal substance), is described in the assessment literature.
- Liquid extract / tincture: Tinctures are among the forms used in both herbal and homeopathic medicine.
- Fresh or freeze-dried herb: Stinging nettle is used as a vegetable green, juice, tea, and freeze-dried product.
- Homeopathic preparation: The whole annual nettle herb, including its flowers and roots, is used to prepare the homeopathic medication Urtica urens. The fresh parts of the plant are chopped into fine pieces and soaked in alcohol; the final solution is strained and diluted to desired levels to obtain the homeopathic remedy, which is used most commonly for hives.
2. Traditional and Historical Use
Stinging nettle herb has been used since ancient times. The ancient Greeks were familiar with its effects. Dioscorides wrote about it in his work; he regarded it as a tonic, diuretic, digestive, blood-purifier, antitussive, styptic, and an aid in wound and carbuncle healing. In the 16th century, Dioscorides's book was the main source of information on the healing characteristics of nettle.
Greek physicians Dioscorides (first century C.E.) and Galen (ca. 130–200 C.E.) reported that nettle leaf had diuretic and laxative action and was useful for asthma, pleurisy, and for the treatment of spleen-related illness.
In the 1st century CE, the ancient Greek physician Pedanius Dioscorides recommended the use of Urtica urens as well as Urtica dioica for treating nosebleeds, worsening injuries, and belated menstruation.
Lehnhardt used Urtica dioica and Urtica urens for dropsy. Quarin, Deider (1746), and Rosner used nettle for cough, cutaneous eruption, and as a styptic.
In Germany, stinging nettle herb is licensed as a standard herbal tea for diuretic action. It is also used as a component of prepared medicines intended for supportive treatment of rheumatic ailments and irrigation therapy in inflammatory conditions of the lower urinary tract.
Since ancient times, people have taken advantage of the sting by flailing arthritic or paralytic limbs with fresh stinging nettle to stimulate circulation and bring warmth to joints and extremities in a treatment known as "urtication."
During the primordial period, annual nettle was also a source of food and supplied fiber to manufacture cloth. The plant was so popular among the people in ancient times that many regarded Urtica urens to be a better quality plant compared to flax and hemp. Apart from its other uses, Urtica urens has been extensively used for therapeutic purposes.
In South American popular medicine, the aerial parts of U. urens are commonly used to promote diuresis, detoxification, manage diabetes, and alleviate rheumatism. The plant has also been employed to alleviate muscular or minor joint pain.
Stinging nettle herb is used in German homeopathy in treatments for urticaria, herpes, eczema, and hypersensitive reactions.
3. Key Constituents and Active Compounds
According to DAB 10-Kommentar (1991) and Wichtl (2004), nettle leaves contain 1–2% flavonoids, particularly glycosides and rutosides of quercetin, kaempferol, and isorhamnetin.
The herbal substance contains silicates in a relatively large quantity (1–4% SiO₂), partly as water-soluble silicates. Characteristic components are scopoletin, sitosterol with its 3-O-β-D-glucoside, and caffeic acid esters. Other constituents include chlorophyll (approximately 2.7%), proteins, fats, carbohydrates, traces of nicotine, and in the stinging hairs, small amounts of acetylcholine, serotonin, formic acid, and leukotrienes.
Beta-sitosterol, trans-ferulic acid, dotriacontane, erucic acid, ursolic acid, scopoletin, rutin, quercetin, and p-hydroxybenzalcohol are among the constituents found in Urtica species that may be applied for preventive or therapeutic purposes.
Essential ketones (38.5%), esters (14.7%), free alcohols (2%), nitrogenous compounds, phenols, aldehydes, beta-sitosterol, formic acid, acetic acid, chlorophyll and phytol, vitamins, and carotenoids are found in the aerial sections. Many organic acids have also been identified in the aerial parts, including caffeic, ferulic, caffeoylmalic, chlorogenic, and sinapic acids, according to chromatographic examination.
Flavonoids including isorhamnetol 3-O-glucoside, quercetol 3-O-glucoside, kaempferol 3-O-glucoside, isorhamnetol 3-O-rutinoside, and quercetol 3-O-rutinoside have been extracted and identified in flowers, in addition to beta-sitosterol, beta-sitosterol glucoside, and scopoletin, which are found in all sections of the plant.
Fifteen hydroxycinnamic acid derivatives and sixteen flavonoids, flavone and flavonol-type glycosides have been identified in hydroalcoholic extracts from aerial parts of Urtica dioica L., Urtica urens L., and Urtica membranacea using HPLC-PDA-ESI/MSⁿ. Among them, two p-coumaroyl-caffeoylquinic acid isomers were identified for the first time in Urtica urens.
A particularly notable constituent identified by recent in vitro research is chlorogenic acid. The extract's analysis revealed the presence of polyphenols and flavonoids, with chlorogenic acid identified as the predominant polyphenol in the ethanolic extract of aerial parts.
In terms of antioxidant content, the 70% ethanol extract of Urtica urens showed the highest values of total phenolics (31.41 mg GAE/g DW), flavonoids (6.81 mg quercetin/g DW), tannin (8.29 mg GAE/g DW), and TEAC (560 mmol Trolox/g DW); and DPPH radical scavenging for the ethanol extract (95.56%) was higher than that of the aqueous extract (64.56%) at a concentration of 40 mg/L.
Research showed that the ethanolic extract contained the highest amount of total phenolics, flavonoids, tannins, ortho-diphenols, and flavonols.
Sting-Fluid Constituents
The liquid contained in the hairs of a nettle — which causes it to sting — is composed of formic acid and leukotrienes in modest amounts, 1% acetylcholine, 1 in 500 to 1 in 2000 histamine, and 5-hydroxytryptamine (serotonin).
Root Constituents
Phytosterols, lignans, polysaccharides, and the lectin UDA (Urtica dioica agglutinin) have been discussed in the literature as being among the active principles of nettle root, however data were not seen to be sufficient for a conclusive evaluation. The roots contain polysaccharides (glycans, glucogalacturonans, arabinogalactan acid), fatty acids, lectins, ceramides, terpene diols, and terpene diol glucosides.
4. Scientific Evidence by Area of Use
4.1 Anti-Inflammatory Activity
In the carrageenan-induced paw edema model in rats, U. urens showed outstanding anti-inflammatory efficacy. An extract of its aerial parts revealed a percentage inhibition of 41.5% at 300 mg/kg i.p. in the case of hind paw edema in rats.
The most directly Urtica urens-specific study in the peer-reviewed literature is that of Marrassini et al. (2010), published in Phytotherapy Research (PMID: 20564509). Marrassini C, Acevedo C, Miño J, Ferraro G, and Gorzalczany S evaluated antinociceptive and anti-inflammatory activities as well as phytochemical analysis of aerial parts of Urtica urens L., published in Phytother Res 2010 Dec;24(12):1807–12. In the carrageenan-induced hind paw edema in rats assay, the extract provoked a significant inhibition of the inflammation (45.5%, 5 hours after treatment), and myeloperoxidase (MPO) activity was markedly reduced (maximum inhibition 71.7%). The extract also exhibited significant and dose-dependent inhibition. These are preclinical (animal model) results; no human clinical trials with U. urens-specific extracts for rheumatic or musculoskeletal inflammation have been published to date.
In Europe, traditional herbal medicinal products containing Urtica dioica and Urtica urens are indicated for the relief of minor articular pain (EMEA, 2008).
Strength of evidence: For anti-inflammatory and antinociceptive effects, the evidence is currently limited to animal models and in vitro studies. No controlled clinical trials in humans have been conducted specifically on U. urens extracts for inflammation.
4.2 Anti-Inflammatory Effect on Skin (In Vitro)
A 2025 study published in PMC (PMC12745363) investigated the anti-inflammatory properties of an ethanolic extract of U. urens specifically on human keratinocytes challenged with lipopolysaccharide (LPS). This investigation sought to determine the anti-inflammatory properties of an ethanolic extract of U. urens through the use of an in vitro model involving keratinocytes stimulated with LPS. In particular, the research examined the extract's effects on the generation of nitric oxide (NO), the expression of pro-inflammatory cytokines, and its wound healing potential.
The extract's analysis revealed the presence of polyphenols and flavonoids, with chlorogenic acid identified as the predominant polyphenol. Notably, it effectively counteracted the LPS-induced elevation in NO production and also reduced release of pro-inflammatory cytokines such as IL-6, TNF-α, and IL-1β. Additionally, the extract exhibited the potential to accelerate wound closure in an in vitro setting. The findings suggest that U. urens extract may hold therapeutic potential as a topical treatment for chronic inflammatory skin conditions.
Strength of evidence: In vitro only. Promising mechanistic findings, but no controlled human studies have followed from this line of research to date.
4.3 Antioxidant Activity
Research demonstrated that U. urens displays high potential as a natural source of minerals, phytochemicals, and antioxidant properties. The ethanolic extract showed the highest amounts of total phenolics, flavonoids, tannins, ortho-diphenols, and flavonols, and it decreased paw oedema after carrageenan administration while ameliorating the activities of antioxidant enzymes such as catalase (CAT).
During primary antioxidant activity, caffeic acid — present in Urtica species — reacts with generated free radicals by donating electrons or hydrogen, thus neutralizing them to stable products.
Strength of evidence: Antioxidant activity has been demonstrated in vitro and in animal models. There are no human clinical trials establishing antioxidant outcomes specifically for U. urens.
4.4 Diuretic Use and Urinary Tract Support
The EMA's Committee on Herbal Medicinal Products (HMPC) concluded that, on the basis of long-standing use, diuretic herbal tea combinations containing U. urens leaf can be used in minor complaints affecting the urinary tract to increase production of urine in order to achieve flushing of the urinary tract.
The leaf is described in official literature as a diuretic, for example to enhance renal elimination of water in inflammatory complaints, and for irrigation therapy for inflammatory diseases of the lower urinary tract and in the prevention and treatment of kidney gravel. The formal traditional indication adopted by the EMA HMPC reads: "Traditional herbal medicinal product to increase the amount of urine to achieve flushing of the urinary tract as an adjuvant in minor urinary complaints."
Strength of evidence: The diuretic indication is supported exclusively by traditional use evidence, as formally recognized by the EMA HMPC under the traditional use registration pathway. No modern controlled clinical trials have confirmed this effect specifically in U. urens.
4.5 Benign Prostatic Hyperplasia (BPH) / Lower Urinary Tract Symptoms (LUTS)
The root of both Urtica dioica and Urtica urens — often combined or used interchangeably — has been studied in the context of lower urinary tract symptoms associated with BPH. The effect of different nettle root preparations on BPH was evaluated in older in vitro and in vivo pharmacological studies. Only a few components of the active principle have been identified and the mechanism of action is still unclear. Phytosterols, lignans, polysaccharides, and the lectin UDA have been discussed in literature to be among the active principles; however, data were not seen to be sufficient for a conclusive evaluation.
Eight randomised, double-blind, placebo-controlled clinical studies can be found in the literature for nettle root preparations in BPH, though these predominantly used U. dioica root or combined species preparations, and their specific attribution to U. urens alone is limited.
The American Urology Association's updated guideline (2021) for the management of lower urinary tract symptoms attributed to BPH could not make any positive recommendations about supplements and nutraceuticals, including stinging nettle, due to variable results, methods, and quality of studies. The European Association of Urology's 2022 updated guideline on management of non-neurogenic male lower urinary tract symptoms makes no specific recommendation but references the European Union herbal monograph for the traditional use of U. dioica or U. urens radix for LUTS related to BPH, after serious conditions have been excluded; this use is based on sufficient safety data and plausible efficacy from long-standing use and experience.
In the literature, it was discussed that sex hormone binding globulin (SHBG), aromatase, epidermal growth factor, and prostate steroid membrane receptors may be among the mechanisms through which nettle root preparations act in the context of BPH, though none of these has been conclusively established.
Strength of evidence: Weak to moderate for BPH-related outcomes when nettle root preparations (including species mixtures) are examined. Evidence specifically isolating U. urens root is not available. Major guideline bodies consider the evidence insufficient for a formal recommendation.
4.6 Antinociceptive (Pain-Relief) Activity
Anti-inflammatory and analgesic effects in animal models and in vitro assays have been reported in Urtica dioica, Urtica urens, and Urtica macrorrhiza of the Urticaceae family. The Marrassini et al. (2010) study (referenced in sections 4.1 above) represents the primary direct investigation of antinociceptive properties of U. urens aerial parts in rodent models; it demonstrated significant activity in standard experimental pain assays, but again these are preclinical data.
These results are in agreement with those reported for U. urens (another species of Urtica), as noted in parallel antinociceptive studies on related species.
Strength of evidence: Preclinical animal data only. No human analgesic trials on U. urens-specific preparations exist.
4.7 Antimicrobial Activity
Studies evaluating the in vitro antimicrobial activities of ethanol and aqueous extracts of leaves of Urtica urens against strains of bacteria known as multi-resistant organisms or involved in diverse pathology have been conducted. These investigations are purely in vitro and do not constitute evidence of clinical efficacy in humans.
Strength of evidence: Preliminary in vitro data only.
5. Body Systems and Health Areas
The herb is primarily recommended as an adjuvant treatment of rheumatic conditions, lower urinary tract infections, as a nutritional tonic, and more recently the fresh freeze-dried leaves for the treatment of allergies. The root is used to reduce complaints associated with benign prostatic hyperplasia.
Based on traditional use records and the available scientific literature, the body systems and health domains with which Urtica urens is most closely associated include:
- Urinary system: Traditionally used as a diuretic; formally recognized by the EMA HMPC for flushing of the urinary tract in minor urinary complaints.
- Musculoskeletal / Rheumatic system: Used as a component of prepared medicines intended for supportive treatment of rheumatic ailments.
- Skin: Used in German homeopathy for urticaria, herpes, eczema, and hypersensitive reactions. Emerging in vitro evidence suggests potential utility in inflammatory skin conditions.
- Prostate / Male reproductive: Root preparations used in the traditional management of BPH-related lower urinary tract symptoms.
- Nutritional / Metabolic: Nettles are a very nutritious food, easily digested and high in minerals (especially iron), vitamin C, and pro-vitamin A.
- Haematological (traditional only): Traditionally described as a styptic in haemorrhage of the lungs, haemorrhoids, and heavy menstrual bleeding.
6. Dosage Forms and Reported Dosages
The following dosages are drawn exclusively from official regulatory and pharmacopoeial sources, and reflect what has been reported in the literature for preparations of Urtica dioica L. / Urtica urens L. leaf (folium), which are treated as interchangeable in these documents:
- Infusion (herbal tea): A daily dose of 8–12 g of herbal substance as an infusion, as cited by Blumenthal et al. (1998) and Wichtl (2004). The daily dosage is equivalent to 8–12 g of herbal substance. Prepared by pouring one cup of boiling water over 2–4 teaspoonfuls (approximately 2–4 g) of nettle leaves.
- Dry extract: 536 mg dry extract from Urticae folium (8–10:1), extraction solvent ethanol 50% (v/v), as a single dose up to twice daily (equivalent to 2 × 4.8 g of herbal substance).
According to the EMA HMPC Community Herbal Monograph, use of nettle leaf preparations should not extend beyond 4 weeks without reassessment (some preparations are specified at 2–4 weeks).
7. Safety Considerations and Interactions
Adverse Effects
The frequency of the below-mentioned adverse effects is not known. Gastrointestinal complaints such as nausea, heartburn, feeling of fullness, flatulence, and diarrhoea may occur. Allergic reactions, i.e., pruritus, rash, and urticaria, may also occur.
Mild gastrointestinal complaints (e.g., nausea) have been identified. No case of overdose has been reported.
Contraindications
Hypersensitivity to the active substance(s) is a contraindication.
Drug Interactions
Derived from preclinical pharmacodynamic studies, excessive use of nettle preparations may interact with concurrent therapy for diabetes or high blood pressure.
Related to the vitamin K content of nettle herb, it is very low at 0.16–0.64 mg/100 g. The maximum daily dose of a nettle herb preparation, equivalent to about 15 g of dried herb, contains 24–96 micrograms of vitamin K. These values are less than 1% of the therapeutic dosage range of vitamin K (10–20 mg/day), and thus no interaction related to this vitamin is expected.
According to the EMA HMPC Community Herbal Monograph for Urtica dioica L. / Urtica urens L., folium, no drug interactions have been formally reported.
Pregnancy and Lactation
Safety during pregnancy and lactation has not been established for nettle leaf preparations, per the EMA HMPC monograph. No clinical studies are available on this subject.
Pre-existing Conditions
If minor urinary tract complaints worsen and symptoms such as fever, dysuria, spasm, or blood in the urine occur during the use of nettle preparations, a healthcare professional should be consulted.
Reproductive and Genotoxic Safety
Tests on reproductive toxicity, genotoxicity, and carcinogenicity have not been performed on nettle leaf preparations, as noted in the EMA HMPC documentation.
8. Regulatory Status
The EMA's HMPC has formally concluded that Urtica dioica L. and Urtica urens L., folium (nettle leaf), on the basis of long-standing use, may be included in diuretic herbal tea combinations used in minor complaints affecting the urinary tract to increase production of urine in order to achieve flushing of the urinary tract. This is a traditional-use classification, not a "well-established use" classification requiring full clinical dossiers.
The ESCOP (European Scientific Cooperative on Phytotherapy) has published a monograph, Urticae folium/herba (Nettle leaf/herb), whose most recent online edition dates from 2018, covering both U. dioica and U. urens as medicinal plant substances.
9. Evidence Summary and Limitations
The body of evidence specifically focused on Urtica urens — as distinct from the more extensively studied Urtica dioica — is comparatively small. The most important caveats are:
- Species conflation: A major problem in assessment of literature on nettle is that there is not always a clear differentiation between nettle herb and nettle leaf, and most clinical and pharmacological studies do not clearly distinguish between the two principal species (U. dioica vs. U. urens).
- Preclinical dominance: The available evidence for anti-inflammatory, antinociceptive, and antioxidant effects of U. urens specifically derives almost entirely from animal models and in vitro experiments. No well-designed, adequately powered human randomized controlled trials have been reported for any indication using U. urens alone.
- Traditional use recognition: The formal regulatory recognition by the EMA HMPC for the diuretic-flushing indication and by the European Association of Urology (for root preparations in BPH-related LUTS) is based on traditional use data, not prospective clinical trials.
- Except for U. dioica, which has been extensively studied for various pharmacological properties, few Urtica species have been investigated for their biological activity, including U. urens, which has mostly been examined in the context of anti-inflammatory and antioxidant activities.
References
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