Order: Rosales (APG), Urticales (Cronquist)
Family: Urticaceae Juss.
With the name nettle we refer, usually, to the plants belonging to the genera Urtica L. Even though most of them are stinging due to silicized hairs that cover its green surfaces, nettles are usually edible and endowed with important healing properties.
Various species exist, and most of them can be used more or less interchangeably in both kitchen and herbal care. The most known species are: U. dioica (dioecious) and U. urens (monoecious). Some species (like Urtica ferox from New Zealand) are especially dangerous because they can cause harsh skin reactions that last several days, and because, should the extension of the affected skin be very large, they can also engender important central nervous system symptoms.
Nettles are characterized by an inconspicuous flowering (the flowers are tiny and rather unshowy) and anemophily (wind pollination). Even though they offer shelter to a lot of insect species (nettles are stinging only to superior animals, that so tend to avoid touching the plants) and being an important food source for several of them, they are not pollinated by insects.
They usually prefer wet soils or wastelands and roadsides, provided that the soil is enough rich and wet, and avoid the acidic soils. They prefer good concentration of nitrates and phosphates and so they tend to grow near houses and places where animals are present, especially in places where liquid and/or solid manure (rich in nitrogen) accumulates.
Nettles contain good levels of chlorophyll, minerals (especially Ca, K, Si, Mg, Fe, P) and proteins that come from the organication of the abundant nitrogen found in the soil.
Examining their characteristics and “behavior” within their natural environment, we get the impression that the activity of these plants is strongly directed, on one side, toward absorption (hypogeal pole) and organication (epigeal pole) of the nitrogenous substances coming from the wastes of the protein catabolism of superior animals, and, on the other side (exclusively epigean pole), toward the formation of leaves and stalks rich in chlorophyll. With this metabolic activity so strongly characterized, the flowering process seems to stay in the background both from the structural (insignificant flowers) and the functional (pollination is left to wind, so that plant has not to expend resources for activities such as attraction of pollinator insects – production of essential oils , colored molecules, and so on) points of view.
Returning to chlorophyll (indeed, we would better speak of chlorophylls, because various forms exist, all very similar to each other from a structural point of view), it’s interesting to note how chemically similar it appears to heme (contained in the blood of the superior animals), both being cyclic macromolecules, formally derived from a tetra-pyrrolic ring, that contain a metallic ion (Mg in chlorophyll and Fe in heme).
We can also notice a certain similitude between the two molecules also from a functional point of view. First, chlorophyll is a pigment able to “catch” sunlight in order to let the plant use it, during the photosynthesis, as an energy source for the production the “caloric” molecule of glucose. Formally, chlorophyll allows plant to produce glucose and oxygen starting from carbon dioxide and water:
6CO2 + 6H2O -> C6H12O6 + 6O2
On the other hand, heme is a light sensitive pigment (indeed it confers the blood its characteristic red color) that has the task of transporting the oxygen to the animal cells, so that the exactly opposite function, that is, the transformation (“combustion”) of glucose to carbon dioxide and water by means of oxygen, can be performed:
C6H12O6 + 6O2 -> 6CO2 + 6H2O
If the photosynthesis reaction occurs thanks to the energy “taken” from the sun, glucose combustion produces some energy that the animal (or human) body can use to perform its own functions. So, we can say that both reactions together have the overall function of transferring the energy coming from the sun to the animal bodies: these reactions are opposite with respect to the direction, but complementary in the overall action.
A plant so rich in substances that are precious to the superior animals cannot be but strongly appreciated as a food. For this reason, in the course of the evolution it has devised a system to “defend” itself, so that it would not be systematically devoured. The stinging effect is due to the presence, on the surface of leaves and stems, of hard, silicized and hollow, unicellular hairs (trichomes), that, when break, inject a liquid secretion rich in irritating substances (among which histamine, serotonin, acetylcholine, organic acids). The nettle plant trichomes are similar to an elongated ampoule surmounted and closed by a bulb (Fig. 1-A). The whole trichome is calcified and silicized. The silica content is maximum at and around the apex and decreases gradually toward the base of the trichome. The calcification starts together with the decrease of silica, and finally calcium almost replaces silicon near the base [Thurston].
In detail, the silica particles are concentrated maximally at the apex (bulb), where they form a continuous structure (Fig. 1-C zone I). Just below the bulb, we can find a transition zone (Fig. 1-C zone II) almost without silica and, further down, we can see the trichome body (Fig. 1-C zone III), in the walls of which only secondary silica particles are present [Fu].
So, the hardest (due to the silica content) zone is the bulb (zone I), followed by the trichome body (zone III), while the intermediate zone (zone II) is decidedly more fragile and so it can be easily broken. When the trichome is hit, for instance, by an animal, it breaks exactly in correspondence of zone II (v. Fig. 1-B), transforming in a kind of tiny hypodermic needle. Moreover, when the trichome breaks, its cytoplasmatic content leaks toward the external environment, so practically being “injected” into the animal epidermis.
It’s interesting to notice that calcium and silicon are often present together and in inversely proportional concentrations in living systems. In the bones, for instance, silicon, fundamental for tissue calcification, is mainly bound to the newly formed bone matrix: as calcium binds to the matrix, the silicon concentration decreases, so much that the silicon concentration in the completely calcified bone tissue is minimal.
Nettles provide a very durable textile fiber similar to that of flax. A green dye can be obtained from the leaves and stems and a yellow one from the roots. The juice and a decoction of the plant can be used to curdle milk.
Nettle, traditionally, is considered a Martial plant, because of both its “pungency” and its activity: acute, violent, reddening, inflaming, intense, purifying and acting upon blood formation (see also [Angelini, Junius, Culpeper]).
The secondary signature of nettle is Venusian, because of its peculiar action upon kidneys and adrenals and of its ability to purify the body and to treat rheumatism and gout (thanks to the exaltation of Saturn in Libra; see also [Angelini]).
Parts used and their collection
All the parts of the nettle plant are used in therapy: leaves and apical parts collected before flowering, flowering aerial parts (used mostly in homeopathy), seeds (mostly collected when unripe) and roots.
The leaves and apical parts are collected just before flowering. The stems can be cut at the ground level, gathered in bundles (ten stems per bundle maximum), and hung to dry upside down, in a shady, airy and dry room or in a dryer at low temperature. Once dried, the leaves and the apical parts must be separated from the stems that are discarded since they are fibrous.
Alternatively, the leaves and apical parts (collected without the fibrous stems) can be used to make liquid extracts (hydro-alcoholic tincture, vinegar tincture, etc.).
The flowering aerial parts are collected, obviously, when the plant is in full bloom and before the flowers wilt or the seeds start forming. They are mainly used to make an alcoholic tincture.
The seeds should be collected when they are still unripe but already “full”: the floral stems that bring the female flowers before and the seeds after, even though pendulous, tend anyhow slightly upward when the plants are in bloom, but bend decidedly downward because of the weight of the seeds when the latter are “full”: this is the best moment for collecting them. One can choose to collect only the seeds, or to collect the entire flowering stems or the whole apical part of the plant that carries the floral stems and then removing the seeds at a later time. The seeds so collected can be dried or used to make a tincture.
The roots must be collected during the autumn.
The aerial parts of nettles always host a lot of insects so it’s important to remove them before drying or extracting the herb. This can be easily done by putting the collected parts upon a flat surface (table, floor, etc.): normally, the insects go away by themselves in a short time.
For tincturing, the drug/solvent ratio and the alcoholic proof vary a lot according to the traditions. Tinctures can be prepared starting both from fresh and recently dried material: obviously, in the former case the obtained tincture is richer and more effective.
The mother tincture is prepared with fresh plant material, extracting with a 45% alcohol solution (90 proof).
In the American tradition, the drug/solvent ratio (herb weight expressed in oz. and alcohol volume in fl. oz) from 1:2 to 1:5 for the leaves (either fresh or dried), and an alcohol concentration in the 50-90% range (100-180 proof); for the roots and seeds, the drug/solvent ratio is usually 1:3-1:5 and the alcohol concentration about 25-30% (50-60 proof).
Tastes and nature
Nettle taste is primarily sweet and “salty” (it’s a kind of salty taste that Matthew Wood defines “earthen” [Wood]), and secondarily pungent, bitter and slightly astringent. The pungent taste is more evident in the fresh herb (before tasting it, pay attention that the herb is well withered or pounded, so that the hairs have softened and lost their sting), while the sweetness and bitterness can be tasted more easily in the tincture.
Within the western tradition, nettles are considered cooling and drying (see for instance [HerbRem]). The ancient authors (e.g., Matthiolus, Durante and Gerard) consider them slightly warming (it doesn’t reach the first degree of hotness [Gerard]) and drying instead. Castore Durante probably describes its temperature (or nature) in the best possible way:
“It does not warm too much: but it’s composed of very subtle parts, & although being hot outside, & pungent, its burning quality lies on the surface of its fronds, but its cooling virtue is hidden in its interior.” [Durante]
This means that the plant associates a certain degree of hotness, mostly connected to the ability of its surface to sting and inflame (and that reflects however into the “overall” taste and in the stimulating effect of the plant), to a decidedly more cooling action. The fact that nettle has “opposite” properties is very interesting, because it gives the plant the ability to act bivalently: indeed, it’s stimulating and cooling at the same time, being adapt to both “hot” conditions (e.g., inflammation and fevers) and conditions characterized by “heat” deficiency, and in neither cases it appears excessive, inasmuch as each of its qualities is mitigated by the contemporaneous presence of the other one. We say that nettles are ambivalent with respect to the heat degree, with a slight prevalence of heat. Nettles are more pungent when in bloom, so if we prefer a higher heat degree we can collect them when blooming.
The seed, too, is sweet, salty and slightly pungent (more than the aerial parts); it’s hot and dry in the second degree. According to the Chinese Medicine, nettle seeds enter the Kidney and Liver channels and they have the function to supplement Qi, benefit the kidney and engender essence. Nettle seeds are indicated for Kidney Qi vacuity and depleted essence leading to lethargy, fatigue, loss of appetite, weight loss, muddled thinking, low sex drive, etc. The combination of sweet and slightly bitter flavors is common among the supplementing herbs like ginseng: sweetness nourishes, while the slight bitterness gently drains in order to prevent stagnation from the supplementing action of sweetness. Nettle seed is indicated when the Kidney Qi is too weak to draw the breath (or the Lung Qi) in and down, reason why the patient must sit up straight in order to breathe. [Garran]
From the taste and nature (or temperature) of the plant we can infer the principal actions of nettle:
- Nettle is sweet, so it has a supplementing (nourishing), moistening, demulcent and harmonizing action, and may alleviate spasms, pains and convulsions. Being moistening and nourishing, the sweet taste supplements Phlegm, providing the tissues with the correct moisture and nourishment, reason why it is adapt to the conditions of dryness and undernourishment (or atrophy) of tissues. So, nettle supplements the (correct) Phlegm (we may also say that it is a Phlegm tonic or a nourishing tonic).
- Nettle is salty: this taste softens the tissues and the thickened Phlegm and frees the bowels. In small amounts the salty taste moistens the tissues and the body, while in larger amounts it promotes evacuation (and consequently dries). The slight saltiness of nettle contributes to its ability to moisten the tissues (and so to supplement the correct Phlegm), while, at the same time, makes the herb apt to soften the perverted (that is, accumulated or thickened) Phlegm, making its removal easier. Indeed, nettle acts on both sticky mucus (e.g., bronchial catarrh) and mucus that has “hardened” even more because of a certain melancholic component (calculi, polyps, cysts, and so on). So nettle prepares perverted Phlegm for removal.
- Nettle contains a significant amounts of Silicon, Iron and Calcium and Magnesium salts that are able to supplement the correct Melancholy; for this reason, nettle tonifies (or supplements) Melancholy (we can also say it is a Melancholy tonic). The plant has a direct action upon the Spleen, the “great Stone”, the organ that, according to the Hippocratic-Galenic medicine, administrate the melancholic humor (see [Culpeper, Durante, Fuller, Mattioli], but also [Boericke, Clarke] about urens in homeopathy).
- The slightly bitter taste of nettle stimulates the secretion (and so the excretion) of fluids and tends to be abstersive (cleans while drying) and to “alterate” (in the direction of an amelioration) the metabolism burdened by wastes (especially those of phlegmatic and phlegmatic-bilious nature), stimulating the elimination of the latter and restoring the correct operation of body. Plants that do this are called alteratives. Indeed, as we will see below, the alterative action of nettle is also due to its ability to tonify the excretory organs (first among them, the kidneys and the liver). Its slight degree of bitterness drains gently and prevents any possible stagnation due to the tonifying action of the sweet taste; moreover, bitterness also contributes to the slight evacuating action already due to saltiness.
- It’s slightly astringent and this confers it the ability to contract body tissues and to inhibit fluid loss, so reducing transpiration, tissue relaxation and ptoses. For this reason, nettle is indicated for hemorrhages, leucorrhea, diarrhea (also mucous), excessive transpiration, and when the intestine, uterus and blood vessel walls need to be toned up. This makes the plant useful, for instance, in case of leaky gut syndrome, uterine bleeding or prolapse, in the post-partum period, in case of blood pressure problems (nettle modulates the tone of the blood vessels walls) and hemorrhages (even internal ones). Being astringent, it tends to dry the surface of the body (skin, mucous membranes), while incrementing the “internal” body moisture: on the one hand, with its sweetness and slight saltiness, nettle increments the correct Phlegm, while on the other hand, with its astringency, prevents its dispersion.
- The slight pungency of nettle makes the plant stimulating, diffusive and diaphoretic, able to reactivate the metabolic functions when these have “cooled off” and slowed down (especially at the level of kidneys, liver stomach, and pancreas), to move and regulate energy and matter (especially body fluids, lymph and blood included), to resolve infections, putrefactions, the syndromes caused by external factors (fever, colds, etc.) and the blood stagnations (including bruises). The diaphoretic action is strongest when nettle is taken with a hot liquid (i.e., as a hot herbal tea). Nettle is decidedly more pungent when fresh, so much that it may be used as a rubefacient, that is, to counter-irritate the tissue it touches, incrementing the superficial circulation and the local tissue metabolism: for this reason, fresh nettle has been traditionally used to gently whip the skin in order to alleviate rheumatic pains and to “awaken” numbed or paralyzed body parts. The nettle tincture, too, has a stimulating action but, unlike the fresh plant, it is not irritating. So, nettle has a supplementing action upon the “caloric” aspects of the body (we say it supplements Yellow Bile). Moreover, pungency allows nettle to “circulate” the Phlegm “already” prepared for elimination, and to expel it from tissues by means of the lymphatic system.
- Nettle is also a blood tonic, since it nourishes the melancholic aspect of blood, regulates its liquid-phlegmatic and caloric-bilious components, supports its flow (thanks to pungency) and keep it within the vessels (so, according to the Traditional Chinese Medicine, or TCM, nettle enters the Kidney and Liver vessels). According to some authors (for instance, [Tierra]), it cannot be considered a blood tonic in the sense of TCM, too, because it is too “eliminative” (diuretic and alterative) to fully accomplish such a function.
The nettle seeds have similar taste and qualities to those of the aerial parts, but they are sweeter and decidedly more pungent (even if the degree of heat is not high), and so their action is more nourishing, supplementing and diffusive (see also [Garran]).
An important feature of nettle is that it has opposite actions and qualities at the same time:
- it has a slightly hot nature and, at the same time, it’s cooling; indeed, for instance, it’s stimulating but also eliminates the phlegmatic-bilious wastes (it has an ambivalent action upon Yellow Bile);
- it’s nourishing and, at the same time, “eliminative” (alterative);
- it’s diaphoretic (increases perspiration) and astringent (limits fluid loss);
- it supplements the correct Melancholy and Phlegm but, at the same time, helps to reduce the corresponding perverted humors, since, as we have seen, it treats indurations (calculi, polyps, cysts, but also bruises) and accumulated or thickened Phlegm: we will say therefore that is a regulator of Melancholy and Phlegm.
The plants that are able to exert “contrasting” effects (we more correctly say these plants have bivalent or ambivalent effects) are particularly important in herbal therapy, because, on the first place, they can be used in multiple contexts and, secondly, because, instead of inducing or limiting certain body functions, they are rather able to “fine tune” them, reducing a function that is too activated or stimulating a function that is reduced.
So, we can summarize the main actions of nettle as follows:
- it regulates Phlegm and acts, at the same time, as a nutritive tonic and as an alterative, stimulating the removal of phlegmatic and phlegmatic-bilious wastes and stagnations, even those “hardened” due to a certain melancholic component;
- it regulates Melancholy (also acting upon the Blood);
- it stimulates the metabolic functions in general.
Moreover, nettle is a kidney trophorestorative (see below the paragraph “Kidneys, adrenals and urinary tract“).
The clinical actions of nettle derive from the humoral actions. Nettle is a nutritive tonic, a kidney trophorestorative, a blood tonic, a metabolism stimulant, an alterative, diuretic, hemostatic, galactagogue, emmenagogue, analgesic, vulnerary, antiallergic herb.
Even though nettle has an important action on the whole body, it nevertheless has a particular affinity for some specific organs, tissues and systems, among which: kidneys and adrenals, spleen, liver, stomach, pancreas, blood, epithelia (skin, mucous membranes, blood vessel walls), prostate and uterus.
Nettle, as we have seen, is characterized by ambivalence: on the one hand, it treats deficiency conditions and, on the other hand, excess conditions. This feature reflects clearly on its indications.
The ability to supplement Phlegm and Melancholy tonic, together with the interesting nutritional profile, makes nettle particularly suited for deficiency conditions: undernourished, thin, weak, pale, emaciated people that lack vitality. It reinforces the connective tissue, supports the protein metabolism, treats the deficiencies of iron and corpuscular components of blood, stimulates milk production.
On the other hand, it can treat excess conditions as well, particularly those of Phlegm and Phlegm-Bile excess (according to the TCM, the former corresponds to the Damp or Phlegm patterns and the latter to the Heat/Dampness patterns). In these conditions tissues are swollen due to fluids more or less “thickened”, and a concomitant inflammation may also be present: in these cases, nettle drains the excess fluids while “quenching” the tissue heat. Nettle can therefore be used to treat the so called “bad blood syndrome” and its symptoms: chronic skin diseases, low grade infections (chronic but not overly intense), accumulation of Phlegm in tissues, digestive problems and liver “sluggishness”.
According to some authors ([EvolHerb, Riley]), nettle is also effective on choleric people that tend to have outbursts of anger, with red, bloodshot eyes, red face, general irritability, and frustration (these are symptoms that may correspond to some TCM syndromes, from Liver Qi stagnation to Liver Fire raising).
Ambivalence can also be found among the homeopathic mind symptoms: calm, relaxed, easy, euphoric, witty people; or, rather, detached, separate, unsympathetic, irritable at work, and fearful, with dreams of panic about survival [Riley].
The seeds have an anti-enuretic (they treat “bed wetting”) and expectorant action; are indicated in case of cough (Dioscorides recommend to take them macerated with honey in wine); restore the kidney functions and are really useful in chronic renal failure (in clinical practice, they have prevented resorting to dialysis in several cases). In the latter case, the dried or tinctured immature seeds are the best.
For all these reasons, nettle is an extremely versatile herb, so much that David Hoffman, a well know Medical herbalist, says: “When in doubt, try nettles!”
Due to the complexity of its action, nettle can be used to address even profoundly different humoral conditions. In particular, this herb is indicated in case of Yellow Bile deficiency, Phlegm deficiency, Blood deficiency, Phlegm excess and Yellow Bile excess. In the clinical practice we can also find mixed cases, characterized by the commingling of two or more of these conditions.
Below the general traits of such humoral conditions are described.
Yellow Bile deficiency
Generally it corresponds to the Depression tissue state [Wood] and to different Yang deficiency conditions according to the TMC (for instance, in the case of nettle, typically Yang Qi deficiency or Kidney Yang deficiency). It occurs in weak, pale, sluggish people that lack vitality, and experience functional deficiencies, like, for instance, difficult digestion and elimination, low blood pressure and possibly orthostatic hypotension, impotence. According to the severity of the condition, they can have:
- a weak, slow, deep pulse;
- a grayish or pale-grayish, cold, atrophic and impure skin (e.g., acne, pimples);
- a tongue that is typically pale or dark/grayish, wet and sometimes swollen, with a thin or thick, white (or, in case of secondary infections, white-yellowish or yellow/brown in the most serious cases) coating. Sometimes the coating is coagulated (caseous).
It corresponds to the Atrophy tissue state [Wood] and to some different forms of Yin deficiency according to the TCM. Undernourished, thin, weak, emaciated people, with dry mucous membranes and dry skin that cracks or desquamates easily (skin diseases like acne, eczema and psoriasis are very common), constipation and dry stools, possible restlessness or nervousness. They can have:
- a narrow, weak pulse that can tend to be floating (it sometimes “scrapes”); sometimes it is slightly tense at the left wrist;
- a dry skin, missing oil, water or both; it may have the tendency to desquamate;
- a dry tongue with no coating (always); sometimes the tongue is thin or cracked.
It corresponds roughly to the Blood deficiency of TCM. As we have already seen, nettle is a blood tonic, but, according to some authors, it’s not able, alone, to fully treat the Blood deficiency according to the TCM because, due to its “eliminative” (diuretic and alterative) actions, this herb is not able to increase the Blood “volume”. Nettle is specially indicated to treat iron deficiency and the conditions where the proteic or corpuscular components of blood (red and white cells, platelets) are low. These conditions are often characterized by dizziness and vertigo, palpitations even intense, insomnia, profuse dreaming, memory lapses, hair loss or discoloration. They can have:
- a thin, weak pulse;
- a pale or yellowish skin, without luster; pale coloration of the mucous membranes (for instance, palm of the hand, auricle, eyelid conjunctiva, inner mucous membrane of the lip) and of the nail bed;
- a pale tongue; it may also be dry.
It corresponds to the Torpor/Stagnation tissue state [Wood], to the “bad blood syndrome”, or to the Internal Dampness or Phlegm conditions of the TCM. Accumulation or loss of fluids, that are more or less thick or turbid; turbid urine; a feeling of heaviness of the body or mental confusion and dullness; heavy, thick and adhesive mucus on the mucous membranes or in the stools, excessively frequent swallowing or spitting of saliva that is usually thick; feeling of intoxication or symptoms similar to hangover; low immunity; weak peripheral circulation, with skin lesions and slow-healing wounds; slow elimination, with possible constipation. Possible wet eczema, arthritic or rheumatic pains, atherosclerosis, allergy. Patients can have:
- a slippery or wiry pulse;
- a yellowish or whitish, dull, impure or viscous, greasy skin, possibly with excessive perspiration and/or acne;
- a pale tongue with a large body, usually flaccid, apathetic or atonic, with a viscous or slippery, white (or yellowish, in case of concomitant heat), more or less thick coating; “sticky tongue”.
Yellow Bile excess
It corresponds to a condition of heat excess and hyper-activity, typical, for instance, of the Excitation tissue state [Wood]. It can also correspond to the TCM heat excess conditions (for instance, Full Heat, excess Heat in the Liver that can lead to Liver Fire raising, but also Heat as a component of mixed conditions like Damp/Heat or Toxic Heat). Hyper-stimulation, body hyperactivity that produces heat, reddening, sometimes pain; temperature raising, fever; nervous excitability, restlessness; sensibility to stimulation; red eyes; red-pinkish color of tissues. Or, unsympathetic, detached, choleric people with tendency to outbursts of anger, general irritability, red face, frustration and anger; eyes may be red, bloodshot. According to the specific conditions, patients can have:
- a quick pulse; it can also be overflowing, or full and possibly wiry;
- a red tongue; it can be redder on the sides if the liver is affected; the coating is yellow and dry, even more so as the Heat becomes more intense.
In case of hyper-reactivity, in order to prevent an overstimulation, it is advisable to use a low dosage of nettles, for instance, 1-5 drops of the tinctured aerial parts, up to 3 times a day, incrementing gradually the dosage only if needed.
Burns and seasonal allergies, too, can be included (even if the latter not exactly with full rights) in this humoral condition. In particular, nettle has a specific indication for allergies with red nose and eyes and abundant loss of “subtle” transparent fluids (tearing and dripping nose).
- Mental dullness, lack of concentration and mental acuity [Wood]
- Memory lapses [Wood]
- Dead fish dullness of the eyes, without luster, drooping eyelids [Wood]
- Tired, hard to get out of a chair and get going; rises with a sigh or grunt, but stays on task once activated; begins the day slowly, hard to stop at the end of the day [Wood]
- Yawning, sighing, sleepiness [Wood]
- Mental dichotomy: calm, relaxed, easy, euphoric, witty people; or, rather, detached, separate, unsympathetic, irritable at work, and fearful, with dreams of panic about survival [Riley]
Cardiovascular system and blood
Nettle (aerial parts) has a peculiar action on blood, since it is able to restore a low iron blood level and a low concentration of red cells, neutrophils and lymphocytes [De Vico, Juma, Saeidi]. It increases albumin and the total protein level in serum [De Vico, Saeidi]. It has an ambivalent effect on blood pressure, since it is able to treat both hypotension and hypertension. It reduces platelet hyperaggregability [ElHaouari, Mekhfi].
- Iron deficiency, low red cell count
- Low blood pressure; with fainting on raising [Wood]
- High blood pressure
- Low total protein or low albumin in blood
- Mucus, bronchitis, asthma; especially with grayish-pale skin color (aerial parts, plant juice, roots) [Durante, Gerard, Giannelli, Mattioli, Wood]
- Pleuritis [Gerard]
- Cough, whooping cough [Durante, Gerard, Giannelli,]
- Nasal polyps (leaves or seeds ground and put into the nose) [Culpeper]
- Inflammations of the throat; uvula relaxation (as a gargle) [Culpeper, Gerard, Mattioli]
Digestive system and metabolism
Nettle (aerial parts) has a tonic and slightly laxative action on bowels; it treats intestinal inflammation, removing any irritative stimuli that may cause it [Iozzi]. Nettle stimulates biliary, pancreatic and enteric secretions, improving digestion (its action is also due to small quantities of secretin). It’s a mild stimulating laxative.
- Diarrhea, dysentery, also chronic ones; mucus in stools [Wood]
- Intestinal inflammation, intestinal gas [Giannelli, Mattioli, Iozzi]
- Diabetes [Grieve, HerbRem]
- Gout; with pains at the right deltoid [Clarke, Culpeper, Driope, Grieve, HerbRem, Reckeweg, Schwabe, Vermeulen]
Kidneys, adrenals and urinary tract
Nettle has an important and broad-range action upon these organs, since it stimulates diuresis (it’s a mild diuretic that expels sodium, urea and urates), eliminates urinary calculi (whichever be their location), treats infections (especially the long lasting ones) and tones up tissues. It’s a renal trophorestorative, useful in case of kidney failure, dialysis, any damage (both structural and functional) to the kidneys, and adrenal deficit or “fatigue”. Any part of the plant has a trophorestorative action on kidneys, but the immature seeds are best. The seeds, especially when used fresh, can induce a certain activation of the nervous system: an anecdotal case has been reported of a man that was not able to sleep for three consecutive days after ingesting a tablespoon of seeds [EvolHerb]. It’s important to know that the nettle seeds (either fresh, dried or tinctured) may give different results in people: some people may find them strongly activating and need to use a very low amount, other people may be less sensitive and need greater amounts.
- Kidney failure, dialysis (seeds) [Wood]
- Edema [Wood]
- Urinary calculi; with colic. Gravel. [Giannelli, Wood]
- Chronic or recurrent inflammation of the bladder or the urinary tract; with abundant mucus discharge [HerbRem, Wood]
- Bed wetting
The whole plant (aerial parts and seeds) stimulates the detoxification activity of liver. Some extracts are able to modulate the genic expression of the detoxificating liver enzymes. Specifically, it has been experimentally demonstrated that the seeds of Urtica urens are able to stimulate the induction of some isoforms of the P450 cytochrome [Hizlan]: it’s important to keep this in mind in case of simultaneous intake of drugs and nettle seed dry extracts for extended periods of time. Nettle supports the hepatic protein metabolism. In animals, it bolsters albumin biosynthesis. [De Vico, Saeidi].
- Jaundice (root or strong decoction) [Hill, Quattrocchi, Wesley]
- Hepatic draining
- Scarce hepatic production of proteins
Nettle (aerial parts) tonifies and stimulates the uterus, is emmenagogue and treats heavy menstrual bleeding. It is useful during the post-partum period, in case of uterine atony or prolapse and of dysmenorrhea/amenorrhea. Nettle treats the inflammation of uterine appendages [Iozzi]. Nettle root treats benign prostatic hypertrophy. The seeds are aphrodisiac.
- Aphrodisiac (seeds drunk with raisin wine or must) [Durante, Gerard, Mattioli]
- Male genital system:
- Impotence, difficulty producing and keeping an erection; with low blood pressure [Wood]
- Benign prostatic hypertrophy (root)
- Female genital system:
- Hypermenorrhea; anemia from blood loss [Wood]
- Premature cessation of menses [Wood]
- Scanty periods; amenorrhea, dysmenorrhea (especially if taken with myrrh); “hysteria” [Culpeper, Durante, Mattioli]
- Anemia and low blood pressure during pregnancy [Wood]
- Deficient lactation [Wood]
- Uterus prolapse; “opens the mouth of the matrix” [Mattioli]
Connective tissue and extracellular matrix
Nettle (aerial parts) is able to drain the phlegmatic-bilious and melancholic toxins from the connective tissue (also thanks to the presence of salts and Silicon), and particularly the residuals of the protein catabolism (predominantly urates, see also [Fuller]), and to optimize protein synthesis, resulting in a “cleaning” and tonifying effect on the connective tissue and extracellular matrix. In case of wounds, it promotes collagen formation and stimulates the formation of capillaries, but minimizes the formation of fibrous tissue. Counteracts osteoporosis and the protein degradation of cartilages in case of rheumatoid arthritis. It inhibits (in vitro) some extracellular matrix proteolytic enzymes (elastase, collagenase) [Bourgeois].
Nettle (aerial parts) counteracts skin diseases that manifest with raised, red patches (wheals) that burn and/or itch (hives, insect bites, cold sores, etc.). It is a good vulnerary, and promotes the correct wound healing.
- Cold sores
- Rashes, hives, insect bites; raised, red and burning or itching; with tendency to scratch in a voluptuous way; in case of insect bites, the skin reaction is much larger than the bite (tincture for internal use, or infused oil or tincture for external use).
- Burns; with excess protein burdening the kidneys (tincture: as is, for internal use, or diluted with water for external use, on bandages) [Fuller, Wood]
- Atrophy and paralysis of muscles (voluntary or involuntary); even as a sequela of anesthesia (tincture, whipping with fresh nettles) [Wood]
- Osteoarthritis, rheumatoid arthritis
- Rheumatism [Driope]
- Osteoporosis; possibly with urinary calculi
- Sciatica [Culpeper]
- Uricemia, bilirubinemia
- Fever, intermittent fevers, malaria [Fuller, Grieve]
- Allergy, allergic rhinitis (especially freeze-dried powder or tincture) [HerbRem]
- Vulnerary: wounds, ulcers, gangrenes, fistulas, abscesses; that heal poorly or with pus [Culpeper, Durante, Mattioli]
- Small tumors (growths), mumps [Durante, Mattioli]
Differences between the various species of nettle
The various nettle species have more or less the same effects, so they may be used interchangeably. However, some subtle differences exist.
For instance, according to Dewitte and Leunis, Urtica dioica and Urtica urens have more or less the same properties, even though the former, with a hyper-βγ-, hyper-γ- and hypo-γ-eu-globulinic profile, is indicated in the fibrosis and disorganization phases, while the latter, with a less evolved profile, is indicated in the reaction, deposition and fibrosis phases [DewLeunis].
According to John Gerard, among the (European) nettle species, the most efficacious is Roman nettle (Urtica pilulifera L.) [Gerard].
Methods of administration
Nettle can be taken as a herbal tea, decoction, macerate, hydro-alcoholic tincture or freeze-dried powder. It can also be used as food.
- herbal tea or decoction: 20-30 g (dry leaves), 6-9 g (dry root)
- dry seeds: form 1 teaspoon up to 2 tablespoons a day; start with low doses: it may prove very exciting in some people
- hydro-alcoholic tincture of aerial parts, roots, seeds: from 1 drop up to 2-3 ml, up to 3 times a day (or more, in case of aerial parts tincture); start with low doses of seeds tincture.
Contraindications and collateral effects
Nettle is generally very well tolerated, except for some minor gastric troubles.
Some people may experience headache after drinking a string nettle tea. [HerbRem]
Being drying, nettle may accentuate a pre-existing systemic dryness.
As a diuretic herb, it can interfere with diuretic drugs. The seed dry extracts, used for sufficiently long periods (> 14 days), can interfere with the plasma level of some drugs.
According to the Humoral doctrine, Phlegm is the moist and cold principle, typical of what is liquid, and nourishes; Yellow Bile is the hot and dry principle, responsible of activities in general and of inflammations; Blood is the hot and moist Humor; Melancholy is the cold and dry humor, responsible of all indurations and “structurations”.
 Moreover, photosynthesis “accepts” sunlight in order to produce nutritive substances, so we can say it’s a process governed by Venus, whereas glucose combustion, being an “inflaming” process (and mostly catalyzed by iron), is a Martial process.
 When the tissues lack correct Phlegm, they appear undernourished, withered and dry. Phlegm also “includes” the soluble sugary, salty, fatty and proteinaceous components of body fluids.
 Such melancholic component, from a humoral point of view, can result from the combustion of Phlegm that, at first simply sticky, becomes more and more dry and “hard”: this is known as malankholia balghami (that is, Melancholy produced by the combustion of Phlegm) within the context of the Unani-Tibb medicine.
 The Silicon element, too, is able to normalize Phlegm and to promote the expulsion of toxins.
 Probably, the Calcium and Magnesium salts are responsible of the earthen taste of nettle.
 The movement of matter and energy, the opening of pores, the resolution of putrefactions and infections, the stimulation and counter-irritation are all phenomena connected to heat.
 That is, a remedy that nourish a specific organ or system and restore both its structure and function. In this sense, trophorestoratives are similar to the Yin and/or Blood tonics according to the TCM.