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Urtica dioica, stinging nettle

Summary

Though everyone knows that brushing the plant will cause an uncomfortable burning pain for several hours, many do not equate that effect with 'poisoning'.

Family

Urticaceae

Meaning of the Name

Urtica
From the Latin ‘uro’, ‘to burn’ or, more specifically, ‘to irritate by burning’.
 
dioica
Dioecious. The male and female are different plants.

Common Names and Synonyms

common nettle, stinging nettle, the naughty man's plaything (naughty man = the devil).

How Poisonous, How Harmful?

Urtica dioica, stinging nettle

Urtica dioica, stinging nettle

Formic acid is present and responsible for the initial pain but the longer term effects are caused by histamine, acetylcholine and 5-hydroxytryptamine.

Brushing the plant produces a stinging on the skin of varying intensity. There is almost no-one who has not been stung by the nettle.

Incidents

Many, many millions but few result in damage or effects so severe as to require medical attention. In studies on volunteers, the sting has been found to persist for about twelve hours if left completely untouched.

Urtica ferox is a species unique to New Zealand which is said to have caused one human death as well as numerous deaths of dogs and horses. It is believed to contain an additional neurotoxin to those found in other species of nettle.

Folklore and Facts

rtica dioica, stinging nettle

The poisons are in tiny hairs on the edge and underside of the leaves. Each hair is, effectively, a sealed hypodermic syringe. Brushing passed a hair breaks off the top leaving a sharp end which sticks into the skin. Continuing sideways movement results in the bulb containing the poisons being squeezed so that the toxins are injected. The sideways action is essential to break the tops off and leads to the concept of 'grasping the nettle' which suggests that you can avoid damage to the hairs if you take hold of the plant with no sideways movement.

As many people believe that grasping the nettle is painless as say it is nonsense.

Many sources say it was introduced to Britain by Roman soldiers who expected to need to beat themselves with nettles to keep warm. Given that the nettle dies back in the winter, it would not have been available when it was most needed so, either the story is untrue or the Romans were ignorant of the conditions they would meet.

In his 'The Englishman’s Flora', 1958, Geoffrey Grigson talks about using nettle fibres to make cloth. He cites the 18th century Scottish poet, Thomas Campbell, as writing of sleeping in nettle sheets and eating off a nettle tablecloth. Grigson also says that nettle cloth was found wrapped around cremated bones in a Danish grave from the later Bronze Age suggesting the plant was known in northern Europe long before the Romans arrived.

Grigson, John Gerard and others call Urtica pilulifera the ‘Roman nettle’. Grigson says it was found in Romney in Kent where Julius Caesar landed but then points out that its discovery came long after it had been given the name Roman nettle and ‘long after’ it had been grown by Gerard. Grigson describes its alleged use for keeping warm by Roman soldiers as ‘the tall story’.

Grigson does, however, say that it seems to follow mankind around and talks of it appearing in New England in the 17th century after the arrival of British settlers. This following man around leads to the belief in the Highlands and Islands of Scotland that nettle grows from the bodies of the dead.

Pliny has a lot to say about the uses of the nettle but, even though he served in the Roman army in Germany, he makes no mention of its use as a personal heating system.

rtica dioica, stinging nettle

John Parkinson, in his Theatrum Botanicum, published in 1629, is believed to have been the first to claim that nettle was an import from Italy.

William Camden in his book ‘Britannia’, first published in Latin in 1586 but extensively revised in 1607 and then translated into English in 1610, says that the Romans believed Britain to be a place where giants lived in the mountains and serpents roamed the valleys and a person would need to be mad to voluntarily travel to Britain. He then gives the story of the Romans bringing nettle seeds with them.

It may be, therefore, that the Romans brought nettle to Britain not knowing it was already here and not knowing it would die off in the winter. Equally, nettle may just have come with them in the way that it followed the early settlers to New England.

There is, of course, the added complication of how Roman were the ‘Romans’? The Roman Empire depended on assimilating conquered peoples so many of the invading army were native to other parts of the Roman Empire and, by the time Hadrian’s Wall was built about 150 years after the initial invasion, many of the garrison soldiers were native to England and, thus, well used to the climatic conditions.

On balance, Grigson’s view that soldiers beating themselves with nettles was a ‘tall story’ is, probably, correct.

In June, 2000 researchers from the University of Plymouth published the results of a randomized controlled double blind study of the effect of nettle sting on arthritic pain at the base of the thumb.

The trial was very small involving just 27 people who were given a non-flowering plant, either Urtica dioica or Lamium orvala, deadnettle, and asked to apply the underside of one leave to the skin on the base of the thumb or other painful area once a day for thirty seconds. The patients were warned that they might experience stinging but were told the plants in the trial were all stinging nettles.

All the patients using stinging nettles reported an almost immediate reduction in pain and their diaries revealed a significant reduction in analgesic medication. The researchers concluded that further work was required.

In 2007, the results of a pilot study were published. The study was only intended to test the acceptability of a trial for treating knee pain rather than actually testing the benefits of stinging nettle. It involved only 42 people and found little difference in effect between the Urtica dioica and the non-stinging control. A larger study will be required to see if there is a reliable reduction in pain.