Stinging Nettle

In the past, nettle has been used as a diuretic, to build the blood, for arthritis, rheumatism, improve hair appearance and health (topical) ^{36Reference 36Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

Both Galen and Dioscorides have mentioned the leaf for use with asthma, pleurisy, and spleen conditions, and noted its diuretic and laxative effects ^{36Reference 36Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

In Europe, especially Germany, stinging nettle is used for rheumatic and other inflammatory conditions, prostate diseases, and as a diuretic. ^{36Reference 36Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

In current Western herbal medicine, the root and leaves are used for different conditions. The leaves are used as a diuretic and for arthritis, prostatitis, and allergies. The root, on the other hand, is used mainly for benign prostatic hyperplasia, and to treat or prevent baldness or alopecia. ^{36Reference 36Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

In Brazil, the entire plant was traditionally used for excessive menstrual bleeding, diarrhea, diabetes, urinary disorders, and respiratory conditions. It was also used topically here for a range of skin conditions. ^{36Reference 36Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

In Peru stinging nettle is used for muscular pain, arthritis, ulcers, diabetes, digestive conditions, nosebleeds, and rheumatism. It was also used externally here for a range of inflammatory and pain conditions, as well as head lice. ^{36Reference 36Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

In early North American medicine, the leaves and stems were infused and then soaked into bandages to be used as a type of vulnerary to heal wounds. Early North American herbalist also recommended nettle leaves as a nutritious food for weight loss programs and support ^{36Reference 36Taylor · 2005The healing power of rainforest herbs: A guide to understanding and using herbal medicinals}.

In the past, nettle was used as a source for textile fibers in the place of flax or hemp. The oil was also used as a burning oil in Egypt ^{38Reference 38Bone K · 2013Principles and Practice of Phytotherapy}.

Nettle root is the part used here, and it carries the herb’s strongest human evidence. A large 6-month crossover RCT (n=620) reported that 81% of root-extract patients improved their lower-urinary-tract symptoms versus 16% on placebo, with the International Prostate Symptom Score falling from 19.8 to 11.8 and peak urinary flow improving, while PSA and testosterone stayed unchanged ^{1Reference 1Safarinejad MR · 2005RCTUrtica dioica for treatment of benign prostatic hyperplasia: a prospective, randomised, double-blind, placebo-controlled crossover study — randomised controlled trialView study →}. A German 12-month multicentre RCT of Bazoton-uno (459 mg root dry extract, n=246) found a smaller but statistically significant IPSS advantage over placebo, though without a strong gain in flow rate or residual-urine volume ^{3Reference 3Schneider T · 2004RCTStinging nettle root extract (Bazoton-uno) in long-term treatment of benign prostatic syndrome — randomised, double-blind, placebo-controlled multicentre studyView study →}, and a 60-patient root-extract trial saw improvements in IPSS alongside falls in the inflammatory and oxidative markers hs-CRP and malondialdehyde ^{2Reference 2Karami AA et al. · 2020RCTUrtica dioica root extract on clinical and biochemical parameters in patients with benign prostatic hyperplasia — randomised controlled trialView study →}. The mechanism long proposed is that root lignans such as secoisolariciresinol and the sterol beta-sitosterol compete for sex-hormone-binding globulin, though that rests on older in-vitro binding work rather than a modern trial; more direct experimental evidence shows the root (in a saw-palmetto combination) blunts prostate-cell proliferation and inflammation rather than shrinking the gland — a mouse BPH model found reduced prostate weight, lower Ki-67 proliferation and reduced CD45+ inflammatory infiltrate ^{10Reference 10Pigat N et al. · 2019AnimalCombined Sabal and Urtica extracts (WS 1541) exert anti-proliferative and anti-inflammatory effects in a mouse model of benign prostate hyperplasia — animal modelView study →}. Much of the trial literature, however, tests nettle root combined with saw palmetto (PRO 160/120, WS 1541) or Pygeum, where symptom and nocturia benefits are consistent and comparable to finasteride or tamsulosin — but the combination confounds nettle’s own contribution ^{5,6,7,8Reference 5Sökeland J · 2000RCTCombined sabal and urtica extract compared with finasteride in men with benign prostatic hyperplasia — randomised trialView study →Reference 6Lopatkin N et al. · 2007RCTEfficacy and safety of a combination of Sabal and Urtica extract in lower urinary tract symptoms — placebo-controlled, double-blind, multicentre trialView study →Reference 7Oelke M et al. · 2014RCTFixed-dose combination PRO 160/120 of sabal and urtica extracts improves nocturia in men with LUTS suggestive of BPH — re-evaluation of four randomised controlled trialsView study →Reference 8Krzeski T et al. · 1993RCTCombined extracts of Urtica dioica and Pygeum africanum in the treatment of benign prostatic hyperplasia — double-blind randomised comparison of two dosesView study →}, and the most-cited meta-analysis concluded there was then no convincing evidence for Urtica alone ^{4Reference 4Wilt TJ et al. · 2000Meta-analysisPhytotherapy for benign prostatic hyperplasia — systematic review/meta-analysisView study →}. A related saw-palmetto/nettle combination (ProstaMEV) also improved outcomes in chronic bacterial prostatitis when added to antibiotics, though again nettle’s solo role cannot be isolated ^{9Reference 9Cai T et al. · 2009RCTSerenoa repens with Urtica dioica (ProstaMEV) plus curcumin and quercetin improve the efficacy of prulifloxacin in bacterial prostatitis — prospective randomised studyView study →}.

Gap: The largest solo-root RCTs are single-centre and the pivotal meta-analysis predates them; a well-powered, standardised, independent trial of root extract by itself against a modern comparator is still missing.

Nettle leaf extract lowers blood glucose in type 2 diabetes, and this is the herb’s best-replicated metabolic effect. A 2022 meta-analysis of 13 clinical trials found significant reductions in fasting blood glucose (−17.2 mg/dL), HbA1c (−0.93%), C-reactive protein, triglycerides and systolic blood pressure, while insulin and LDL/HDL cholesterol were unchanged ^{11Reference 11Tabrizi R et al. · 2022Meta-analysisEffects of Urtica dioica on metabolic profiles in type 2 diabetes — systematic review and meta-analysis of clinical trialsView study →}; an independent 2020 meta-analysis of 8 RCTs (401 participants) confirmed the fasting-glucose drop (−18.0 mg/dL) but found no significant change in HbA1c, insulin or insulin resistance, and flagged very high between-study heterogeneity ^{12Reference 12Ziaei R et al. · 2020Meta-analysisThe effect of nettle (Urtica dioica) supplementation on glycemic control in type 2 diabetes — systematic review and meta-analysisView study →}. The best single trial gave 500 mg leaf extract three times daily for three months to insulin-requiring patients and saw significant falls in fasting glucose, post-prandial glucose and HbA1c versus placebo ^{13Reference 13Kianbakht S et al. · 2013RCTImproved glycemic control in patients with advanced type 2 diabetes taking Urtica dioica leaf extract — randomised double-blind placebo-controlled trialView study →}; proposed mechanisms include insulin-secretagogue, PPAR-γ agonist and α-glucosidase-inhibitory activity. Some positive results come from multi-herb formulations, which dilute attribution to nettle ^{14Reference 14Khalili N et al. · 2017RCTSilymarin, olibanum and nettle, a mixed herbal formulation in type II diabetes — randomised, double-blind, placebo-controlled trialView study →}.

Gap: Trials are small, short, mostly Iranian and use non-standardised leaf preparations at varying doses; the fasting-glucose signal is consistent but the HbA1c effect is inconsistent, so durable glycaemic benefit is unproven.

Antioxidant capacity is nettle’s most thoroughly documented biochemical property and is thought to underlie several of its other activities. Across DPPH, ABTS, FRAP and CUPRAC assays, leaf extracts show substantial radical-scavenging and ferric-reducing power, attributed to flavonoids (rutin, quercetin, kaempferol) and phenolic acids (chlorogenic acid, caffeic acid) ^{15,16Reference 15Jaiswal V · 2022ReviewAntioxidant activity of Urtica dioica: an important property contributing to multiple biological activities — reviewView study →Reference 16Uğur Y · 2023In vitroDetermination of phytochemical content by LC-MS/MS, antioxidant capacity and enzyme inhibition effects of nettle (Urtica dioica) — in vitroView study →}. In spontaneously hypertensive rats, leaf extract raised plasma antioxidant capacity and superoxide dismutase and catalase activity while lowering systemic oxidative stress ^{22Reference 22Vajic UJ et al. · 2018AnimalUrtica dioica leaf extract modulates blood pressure and oxidative stress in spontaneously hypertensive rats — animal modelView study →}. A 2022 review catalogues organ-protective antioxidant effects in brain, liver, lung, kidney and reproductive tissue, but notes that human confirmation remains limited to a handful of small studies ^{15Reference 15Jaiswal V · 2022ReviewAntioxidant activity of Urtica dioica: an important property contributing to multiple biological activities — reviewView study →}.

Gap: Nearly all data are in vitro or in animals; antioxidant assays measure chemistry in a tube, not a clinical outcome, and the few human signals are secondary endpoints inside diabetes or BPH trials.

Nettle leaf suppresses several inflammatory pathways, which plausibly ties together its use in arthritis, prostatitis and bowel inflammation. In human chondrocytes, the leaf extract Hox alpha and its constituent 13-HOTrE significantly reduced IL-1β-induced matrix metalloproteinase-1, -3 and -9 — enzymes that drive joint-cartilage breakdown ^{17Reference 17Schulze-Tanzil G et al. · 2002In vitroEffects of the antirheumatic remedy Hox alpha, a stinging nettle leaf extract, on matrix metalloproteinases in human chondrocytes — in vitroView study →}. Leaf and root extracts selectively inhibit cyclooxygenase and lipoxygenase branches in human platelets, and root extract lowers LPS-induced chemokine secretion and COX-2 expression in intestinal cells ^{18Reference 18Francišković M et al. · 2017In vitroChemical composition and immuno-modulatory effects of Urtica dioica extracts — in vitroView study →}; a 2026 study of nine preparations on primary human T-cells found nettle downregulates the activation markers CD25/CD69, cuts interleukin-2 and suppresses NFAT-dependent transcription, with effect size differing markedly by extract type ^{19Reference 19Wilmers A et al. · 2026In vitroComparative study of different stinging nettle preparations regarding their immunomodulating effect on primary human T-lymphocytes — in vitroView study →}. In mouse and rat colitis models, leaf extract (IDS 30) and seed oil reduced TNF-α, IL-1β and IL-6 and clinical disease severity ^{20,21Reference 20Konrad A et al. · 2005AnimalAmeliorative effect of IDS 30, a stinging nettle leaf extract, on chronic colitis — mouse modelView study →Reference 21Genc Z et al. · 2011AnimalThe effect of stinging nettle (Urtica dioica) seed oil on experimental colitis in rats — animal modelView study →}.

Gap: The strongest data are in vitro or in rodent colitis; there is no controlled human trial of nettle for a defined inflammatory disease, and effects vary widely between preparations.

Nettle lowers blood pressure in animal models through a vascular mechanism, but human evidence is only indirect. In spontaneously hypertensive rats, four weeks of leaf extract reduced systolic and diastolic pressure and cardiac index dose-dependently, mirroring losartan ^{22Reference 22Vajic UJ et al. · 2018AnimalUrtica dioica leaf extract modulates blood pressure and oxidative stress in spontaneously hypertensive rats — animal modelView study →}, and a later study in the same model showed anti-fibrotic and anti-inflammatory renal protection with increased eNOS expression ^{24Reference 24Vajic UJ et al. · 2024AnimalUrtica dioica leaf extract dose-dependently modulates oxidative stress in the kidney and exerts anti-fibrotic and anti-inflammatory properties in SHR — animal modelView study →}. Mechanistic work on isolated vessels attributes the effect to endothelium-dependent, nitric-oxide-mediated vasorelaxation plus calcium-channel blockade comparable to verapamil ^{23Reference 23Qayyum R et al. · 2016In vitroMechanisms underlying the antihypertensive properties of Urtica dioica — in vitro/in vivo animal studyView study →}. The only human hint is the −5 mmHg systolic reduction seen as a secondary outcome in the diabetes meta-analysis ^{11Reference 11Tabrizi R et al. · 2022Meta-analysisEffects of Urtica dioica on metabolic profiles in type 2 diabetes — systematic review and meta-analysis of clinical trialsView study →}.

Gap: No dedicated human hypertension trial exists; all direct blood-pressure data are from rats, so the traditional hypotensive/diuretic use remains preclinically supported but clinically untested.

The evidence here is specifically for topical application — the sting itself, not an oral preparation. A double-blind randomised crossover trial (n=27) applied fresh stinging nettle leaf daily for one week to osteoarthritic pain at the base of the thumb, using white deadnettle as placebo, and found significantly greater reductions in both pain and disability scores ^{25Reference 25Randall C et al. · 2000RCTRandomised controlled trial of nettle sting for treatment of base-of-thumb pain — randomised controlled crossover trialView study →}. A small nettle-cream clinical study ^{26Reference 26Rayburn K et al. · 2009Clinical trialStinging nettle cream for osteoarthritis — clinical trialView study →} and a 13-patient pilot of a five-herb-plus-thiamine oral blend ^{27Reference 27Hedaya R · 2017Clinical trialFive herbs plus thiamine reduce pain and improve functional mobility in patients with pain — pilot studyView study →} also reported pain relief, though the latter cannot isolate nettle. The proposed mechanism connects to the anti-inflammatory MMP- and cytokine-suppression data from the leaf ^{17Reference 17Schulze-Tanzil G et al. · 2002In vitroEffects of the antirheumatic remedy Hox alpha, a stinging nettle leaf extract, on matrix metalloproteinases in human chondrocytes — in vitroView study →}.

Gap: The key positive trial is tiny (n=27) and tests a counter-irritant sting, a delivery route unrelated to how nettle is usually consumed; the oral pilot is uncontrolled and combines five herbs.

Nettle’s traditional hay-fever use has a clear in-vitro rationale but weak clinical backing. A nettle extract inhibits histamine-1 receptor activity, mast-cell tryptase, and the prostaglandin-forming enzymes COX-1, COX-2 and hematopoietic prostaglandin-D2 synthase — the machinery of allergic inflammation ^{28Reference 28Roschek B Jr et al. · 2009In vitroNettle extract (Urtica dioica) affects key receptors and enzymes associated with allergic rhinitis — in vitroView study →}. Clinically, a 1990 double-blind RCT of freeze-dried nettle (n=98) rated it higher than placebo on global assessment but only slightly better on daily symptom diaries ^{29Reference 29Mittman P · 1990RCTRandomised, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis — randomised controlled trialView study →}, and a 2017 root-extract RCT found symptom improvement on the SNOT-22 score that was matched by an equally large placebo response, with no change in IgE or IL-4/IL-5 ^{30Reference 30Bakhshaee M et al. · 2017RCTEfficacy of supportive therapy of allergic rhinitis by stinging nettle (Urtica dioica) root extract — randomised, double-blind, placebo-controlled trialView study →}.

Gap: Both human trials are small and neither shows convincing separation from placebo; the mechanistic case is strong but the clinical effect, if real, appears modest.

Nettle protects the liver in chemical-injury animal models. In CCl4-challenged rats, the ethyl-acetate fraction of a whole-plant extract attenuated the rise in serum liver enzymes and tissue oxidative markers and protected HepG2 cells in vitro; the active constituent was isolated as ferulic acid ^{31Reference 31Joshi BC et al. · 2015In vitroHepatoprotective potential of antioxidant-potent fraction from Urtica dioica (whole plant) in CCl4-challenged rats — in vitro and animal modelView study →}. Related work reports protection against aflatoxin- and cisplatin-induced liver damage, consistent with the herb’s general antioxidant activity ^{15Reference 15Jaiswal V · 2022ReviewAntioxidant activity of Urtica dioica: an important property contributing to multiple biological activities — reviewView study →}.

Gap: Every hepatoprotective result is in cells or rodents against an artificial toxin; there is no human evidence, and the effect is essentially a downstream reading of the antioxidant data.

Topical nettle accelerates wound closure in animals, supporting its long traditional use as a vulnerary. A full-thickness wound study in rats found an extract ointment healed wounds in 9 days versus 13 for controls, with faster re-epithelialisation and reduced inflammation, alongside in-vitro increases in keratinocyte proliferation and migration ^{32Reference 32Kasouni AI et al. · 2021In vitroThe unexplored wound-healing activity of Urtica dioica extract — in vitro and in vivo (rat) studyView study →}. A separate rat study reported 92% wound closure by day 11 versus 61% for controls and linked the effect to the triterpene lupeol and to the leaf’s flavonoid and polyphenol content ^{33Reference 33Zouari Bouassida K et al. · 2017AnimalExploring the Urtica dioica leaves hemostatic and wound-healing potential — animal modelView study →}.

Gap: Data are limited to topical use in rodents and in vitro; no human wound-healing trial exists.

The use of nettle root for male-pattern hair loss shares the antiandrogen rationale of its prostate use but has no clinical evidence at all. In a comparative in-vitro screen against finasteride, Urtica dioica emerged as a promising 5α-reductase inhibitor — the enzyme converting testosterone to dihydrotestosterone that drives androgenic alopecia ^{34Reference 34Nahata A · 2014In vitroEvaluation of 5α-reductase inhibitory activity of certain herbs useful as antiandrogens — in vitroView study →}. This is consistent with the antiandrogen mechanisms invoked for BPH ^{34Reference 34Nahata A · 2014In vitroEvaluation of 5α-reductase inhibitory activity of certain herbs useful as antiandrogens — in vitroView study →}, but no human hair-loss trial has tested it.

Gap: Support rests entirely on a single in-vitro enzyme assay plus traditional use; there are no clinical or even animal hair-growth data.

Stinging nettle is generally well tolerated: across multiple BPH and diabetes trials of up to 6–18 months, adverse events were mild, infrequent, and comparable to placebo ^{1,3Reference 1Safarinejad MR · 2005RCTUrtica dioica for treatment of benign prostatic hyperplasia: a prospective, randomised, double-blind, placebo-controlled crossover study — randomised controlled trialView study →Reference 3Schneider T · 2004RCTStinging nettle root extract (Bazoton-uno) in long-term treatment of benign prostatic syndrome — randomised, double-blind, placebo-controlled multicentre studyView study →}. The most common problem is topical — the fresh leaf’s stinging hairs (a mix of formic acid, histamine, serotonin and acetylcholine) cause a transient urticarial contact dermatitis, and rare allergic reactions to nettle pollen are documented. Because nettle leaf can lower blood glucose and, in animal models, blood pressure, it may add to the effect of antidiabetic and antihypertensive drugs, warranting monitoring when combined ^{11,12,22Reference 11Tabrizi R et al. · 2022Meta-analysisEffects of Urtica dioica on metabolic profiles in type 2 diabetes — systematic review and meta-analysis of clinical trialsView study →Reference 12Ziaei R et al. · 2020Meta-analysisThe effect of nettle (Urtica dioica) supplementation on glycemic control in type 2 diabetes — systematic review and meta-analysisView study →Reference 22Vajic UJ et al. · 2018AnimalUrtica dioica leaf extract modulates blood pressure and oxidative stress in spontaneously hypertensive rats — animal modelView study →}; its diuretic action is a further theoretical consideration with other diuretics. Nettle is also a significant dietary source of vitamin K, which is a theoretical concern for patients on warfarin, though this has not been formally studied.

Interactions have been only partially assessed: the additive antidiabetic and antihypertensive effects above are inferred from efficacy trials and animal data, not from dedicated interaction studies, and no formal CYP450 or warfarin interaction study was identified.