Urtica dioica, commonly called stinging nettle, is a herbaceous perennial flowering plant, native to Europe, Asia, northern Africa, and North America, and is the best known member of the nettle genus Urtica. The plants have stinging hairs (trichomes), whose tips come off when touched, transforming the hair into a needle that will inject several chemicals: acetylcholine, histamine, 5-HT or serotonin, and possibly formic acid. This mixture of chemical compounds cause a sting or paresthesia from which the species derives its common name, as well as the colloquial names burn nettle, burn weed, burn hazel.
Other species names formerly accepted as distinct by some authors but now regarded as synonyms of U. dioica include U. breweri, U. californica, U. cardiophylla, U. lyalli, U. major, U. procera, U. serra, U. strigosissima, U. trachycarpa, and U. viridis. Other vernacular names include tall nettle, slender nettle, California nettle, jaggy nettle, burning weed, and bull nettle (a name shared by Cnidoscolus texanus and Solanum carolinense).
Stinging nettles are abundant in northern Europe and much of Asia, usually found in the countryside. It is less gregarious in southern Europe and north Africa, where it is restricted by its need for moist soil. In North America it is widely distributed in Canada and the United States, where it is found in every province and state except for Hawaii and also can be found in northernmost Mexico. In North America the stinging nettle is far less common than in northern Europe. The European subspecies has been introduced into North America as well as South America.
In the UK stinging nettles have a strong association with human habitation and buildings. The presence of nettles may indicate that a building has been long abandoned. Human and animal waste may be responsible for elevated levels of phosphate and nitrogen in the soil, providing an ideal environment for stinging nettles. This seems particularly evident in Scotland where the sites of crofts razed to the ground during the Highland Clearances can still be identified.
Nettle leaf is a herb that has a long tradition of use as an adjuvant remedy in the treatment of arthritis in Germany. Nettle leaf extract contains active compounds that reduce TNF-α and other inflammatory cytokines.
Not only does nettle leaf lower TNF-a levels, but it has been demonstrated that it does so by potently inhibiting the genetic transcription factor that activates TNF-a and IL-1B in the synovial tissue that lines the joint.
A study on healthy volunteers demonstrated the anti-inflammatory potential of nettle. In this study, nettle extract significantly reduced TNF-a and IL-1B concentration in response to stimulation by these pro-inflammatory cytokines.
Another study conducted on forty patients suffering from acute arthritis compared the effects of 200 mg of an anti-inflammatory drug (diclofenac) with only 50 mg of the same drug in combination with stewed nettle leaf.
Total joint scores improved significantly in both groups by approximately 70%. The addition of nettle extract made possible a 75% dose reduction of the toxic drug, while still retaining the same anti-inflammatory benefits with reduced side effects. This study implies that people taking nettle extract could possibly reduce their dose of a COX-2 inhibiting drug, while at the same time protecting against the recently discovered potential adverse of effects of some COX-2 inhibitors, i.e., elevated TNF-a and IL-1B.
An extract from the nettle root (Urtica dioica) is used to alleviate symptoms of benign prostate enlargement. Nettle leaf extract, on the other hand, is what has been shown to reduce the pro-inflammatory cytokines TNF-a and IL-B1.
Cooking, crushing or chopping disables the stinging hairs. Stinging nettle leaves are high in nutrients, and the leaves can be mixed with other ingredients to create a soup rich in calcium and iron. Nettle soup is a good source of nutrients for people who lacked meat or fruit in their diets. The young leaves are edible and make a very good pot-herb. The leaves are also dried and may then be used to make a tisane, as can also be done with the nettle's flowers.
Anti-itch drugs, usually in the form of creams containing antihistaminics or hydrocortisone, can provide relief from the symptoms of being stung by nettles. Many ineffective folk remedies exist for treating the itching, including horsetail (Equisetopsida spp.), leaf of dock (Rumex spp.), Jewelweed, (Impatiens capensis and Impatiens pallida), mud, saliva, baking soda, calamine lotion or soap and water. These methods can cause short relief only through mechanical stimulation such as rubbing or scratching or by cooling.
In Great Britain the stinging nettle is the only common stinging plant, and has found a place in several figures of speech in the English language. To "nettle" someone is to annoy them. Shakespeare's Hotspur urges that "out of this nettle, (danger), we grasp this flower (safety)" (Henry IV, part 1, Act II Scene 3). The common figure of speech "to grasp the nettle" probably originated as a condensation of this quotation. It means to face up to or take on a problem that has been ignored or deferred. The metaphor may refer to the fact that if a nettle leaf is grasped firmly rather than brushed against, it does not sting so readily, because the hairs are crushed down flat and do not penetrate the skin so easily. In the German language, the idiom "sich in die Nesseln setzen", or to sit in nettles, means to get oneself in hot water.
Stinging Nettle has a flavor similar to spinach when cooked, and is rich in vitamins A, C, D, iron, potassium, manganese, and calcium. Young plants were harvested by Native Americans and used as a cooked plant in spring when other food plants were scarce. A soup made from the young shoots is considered a spring delicacy in Scandinavia. Cooking or drying completely neutralizes the toxic components found in this plant. Stinging Nettle should not be consumed after it enters its flowering and seed setting stages, as the leaves develop gritty particles called "cystoliths" which can irritate the urinary tract.