Nettle

Urtica dioica

Family: Urticaceae Part used: Leaves (food/medicine), root (urological medicine)

Key Compounds

• Histamine
• Serotonin
• Formic acid
• Acetylcholine
• Beta-sitosterol
• Lectin (UDA)
• Scopoletin
• Quercetin
• Kaempferol
• Rutin
• Chlorogenic acid
• Caffeic acid
• Polysaccharides

Traditional Use

• Allergic rhinitis — 1990 Mittman RCT showed freeze-dried nettle significantly better than placebo for allergic rhinitis; crucially, the effective form is freeze-dried whole plant, not dried, not cooked, not extracted — the processing method appears to matter for this application
• Benign prostatic hyperplasia (BPH) — *Urtica dioica* root extract (distinct from the leaf) has clinical evidence for improving urinary symptoms in mild to moderate BPH; mechanism involves interaction with sex hormone binding globulin and reduction of prostate tissue proliferation signals
• Anti-inflammatory support — in vitro evidence for inhibition of NF-κB and TNF-alpha; clinical evidence is modest but positive for joint and inflammatory conditions
• Traditional food — among the earliest spring greens in European and Japanese foraging traditions; eaten as a vegetable, in soup, as a tea; one of the most nutritious wild plants available in temperate climates; provides complete protein, iron (one of the richest plant sources), calcium, magnesium, vitamins A, C, and K
• Urtication — deliberate application of fresh nettles to painful joints as a traditional treatment for arthritis; practised in European, British, and some Asian traditions; a 2000 RCT by Randall et al. at Plymouth University found significant pain reduction compared to dead nettle control
• Bronze Age textile fibre — nettle fibre (related to ramie, *Boehmeria nivea*) was used for cloth in Bronze Age and early Iron Age Europe before linen and cotton became dominant; archaeologically documented in pre-Roman European textile sites

The nettle sting is not an accident.

Each stinging hair on the leaf surface is a hollow silica needle with a brittle tip designed to break off on contact and inject its contents into whatever touched it. The contents: histamine, serotonin, acetylcholine. The effect is immediate — a wheal and flare reaction at each injection point, followed by a burning and itching that can persist for hours.

The common explanation that this works like a bee sting — formic acid — is incorrect. The formic acid is present but minor. The primary agents are the histamine and serotonin. This matters if you want to treat a nettle sting: antihistamine cream addresses the actual mechanism.

The plant that evolved this defence system is also food. Young leaves cooked in spring — the sting destroyed by heat — are nutritious, edible, and have been eaten across Europe and Asia for as long as humans have lived in temperate climates. The same plant provided Bronze Age Europeans with textile fibre before linen became widely available.

Meet the plant

A perennial herb, 60–150 cm, with opposite serrated leaves covered in stinging trichomes on both surfaces. Dioecious — separate male and female plants. The small flowers are wind-pollinated; nettle pollen is a common seasonal allergen. It grows in disturbed ground, rich soil, riverbanks, and anywhere nitrogen has accumulated: around human settlements, old building sites, animal enclosures.

Japan has related native species: イラクサ (Urtica thunbergiana and related) growing in moist mountain conditions across the country.

Two very different plants

The leaf and the root are pharmacologically distinct enough to be treated as separate medicines.

The leaf is nutritional and anti-inflammatory. It is rich in iron — one of the most iron-rich plant foods available in temperate climates, with bioavailable non-haem iron supported by vitamin C content in the same leaf. The protein content is significant for a leaf. It contains quercetin, caffeic acid, and other compounds with anti-inflammatory activity. The freeze-dried form was shown in clinical trial to reduce allergic rhinitis symptoms. The cooked leaf is simply a nutritious green vegetable.

The root contains different compounds: beta-sitosterol, Urtica dioica agglutinin (UDA, a lectin), polysaccharides, and scopoletin. These interact with sex hormone binding globulin and reduce signals promoting prostate tissue proliferation. The clinical evidence for nettle root in benign prostatic hyperplasia is genuine — multiple trials show improvements in urinary flow and reduction in BPH symptoms. The root does not sting.

These are not interchangeable. Using nettle leaf for BPH or nettle root for allergies is using the wrong part.

Urtication

Deliberately stinging yourself with nettles for arthritis pain is documented traditional practice across multiple cultures and centuries.

The mechanism makes pharmacological sense. Fresh nettle sting delivers histamine, serotonin, and acetylcholine directly into superficial tissue near the joint. This causes a local inflammatory response — counter-irritant effect — and histamine may act as a local vasodilator improving circulation to the affected area.

In 2000, Randall et al. at Plymouth University tested this in a small RCT. Twenty-seven patients with osteoarthritis of the thumb or finger applied either stinging nettle or dead nettle (control) to the affected joint daily for one week. The stinging nettle group showed significantly greater pain reduction and improved disability scores.

The sample size was small. The trial was single-centre. The treatment is uncomfortable. It has not been replicated in a large trial. But the methodology was sound and the results were statistically significant. The traditional practice has at least one small positive RCT behind it.

The textile history

The stem bast fibres of nettles can be processed into textile fibre. Bronze Age nettle textile has been recovered from archaeological sites in Germany and Denmark, pre-dating widespread linen cultivation in northern Europe. The processing method (retting, breaking, scutching, spinning) is essentially identical to linen preparation.

In the World War I fibre shortage, Germany and Austria cultivated nettles as an emergency textile source. The related Boehmeria nivea (ramie, China grass) is still commercially cultivated in East Asia for textiles. Japanese choma (苧麻) cultivation of ramie for fabric has historical documentation.

The connection between the plant that stings you and the fabric that clothed Bronze Age Europeans is real.

The chemistry

Leaf compounds: Quercetin, rutin, kaempferol glycosides, caffeic acid, and chlorogenic acid contribute anti-inflammatory and antioxidant activity. Iron, calcium, magnesium, vitamins A and C are nutritional components.

Root compounds: Beta-sitosterol (phytosterol with BPH activity), UDA (Urtica dioica agglutinin, a lectin that modulates immune function selectively), scopoletin (coumarin), and polysaccharides.

Sting compounds: Histamine, serotonin, acetylcholine, and small amounts of formic acid in the trichome fluid. Destroyed by heat or drying.

What people actually do with it

As food (most traditional): Young spring leaves (before the plant flowers), blanched in boiling water for 1–2 minutes (destroys the sting), used like spinach. In soup (nettle soup is a traditional European spring dish), as a steamed vegetable, in risotto, in pasta. The flavour is mild, earthy, and slightly mineral. Available in Japanese mountain markets and wild-forageable.

Freeze-dried capsules (for allergic rhinitis): The specific form from the Mittman trial. Take during allergy season. The processing matters for this application.

Nettle root extract (for BPH): 120–360 mg standardised root extract, twice daily. This is specifically root, not leaf. Clinical evidence for reducing urinary symptoms in mild to moderate BPH.

Leaf tea: Dried leaves steeped 10 minutes. Nutritional and mildly anti-inflammatory. Not freeze-dried — different compound profile from what was tested for allergies.

Tincture: Fresh plant or root tincture, 2–4 mL, 2–3 times daily.

Urtication (for joint pain): Fresh plant applied to the painful joint. Uncomfortable. Small trial evidence.

Could you grow this yourself?

Nettle grows throughout Japan in moist mountain conditions. You do not need to cultivate it; finding and harvesting wild spring nettle is straightforward in most of Japan. Wear gloves. Harvest young tops before flowering.

If you want to grow it: it naturalises aggressively and is difficult to remove once established. Contain it or grow in an isolated bed.

Nettle (イラクサ) in Japan

Japan’s relationship with nettle is primarily wild-foraging. イラクサ (irakusa) — the native Japanese species — grows in mountain areas across the country and is sometimes gathered as a spring wild vegetable, eaten boiled or in traditional preparations.

This is not a well-developed culinary or medicinal tradition in Japan compared to the European relationship with nettle. The plant is known; it is not deeply embedded in Japanese food culture or traditional medicine in the way it is in European traditions, where nettle soup is a recognised dish and nettle-based remedies appear in historical herbal texts from Dioscorides onward.

The European medicinal tradition — freeze-dried nettle for allergies, nettle root for BPH — reaches Japan through the Western supplement market. Both are available at supplement retailers. The nutritional supplement positioning (iron, minerals, vitamins) is the primary commercial framing in Japan.

Things you’re probably wondering

What actually causes the sting? Hollow silica needles that break off and inject a mixture of histamine, serotonin, acetylcholine, and trace formic acid. The histamine and serotonin are the primary agents — not formic acid, despite the common comparison to bee stings.

What is urtication? Deliberately applying fresh nettles to painful joints as a treatment for arthritis. Practised traditionally across Europe and Asia. Supported by one small RCT showing significant pain reduction versus dead nettle control.

Why does the form matter for allergies? The Mittman 1990 RCT used freeze-dried nettle specifically. Dried and cooked preparations destroy heat-sensitive compounds. If using nettle for allergic rhinitis, freeze-dried form is the research-supported option.

What is the difference between leaf and root? Completely different compound profiles and applications. Leaf: nutritional, anti-inflammatory, allergic rhinitis. Root: BPH, prostate urinary symptoms. The root does not sting.

Botanical details

The full compound list

See Also

• Dandelion — another nutritious wild plant with overlapping spring-foraging tradition; complementary diuretic and liver properties
• Yarrow — traditional European wound herb with overlapping folk medicine tradition
• Elderberry — another wild plant with European traditional use for respiratory and immune applications

References

• Mittman, P. (1990). Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis. Planta Medica, 56(1), 44–47.
• Randall, C. et al. (2000). Randomized controlled trial of nettle sting for treatment of base-of-thumb pain. Journal of the Royal Society of Medicine, 93(6), 305–309.
• Chrubasik, J.E. et al. (2007). Evidence for effectiveness of herbal antiinflammatory drugs in the treatment of painful osteoarthritis and chronic low back pain. Phytotherapy Research, 21(7), 675–683.
• Krzeski, T. et al. (1993). Combined extracts of Urtica dioica and Pygeum africanum for benign prostatic hyperplasia. Clinical Therapeutics, 15(6), 1011–1020.