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Ruta graveolens, rue

Summary

Some people say that merely being close to rue has caused burns to appear but it may be a reluctance to admit that a supposed mosquito repellent has produced harm.

Ruta graveolens, rue

Ruta graveolens, rue

Family

Rutaceae

Meaning of the Name

Ruta
Often said to be from the Latin for 'bitter' but could be from ‘rutilus’, ‘reddish yellow’ or ‘orange yellow’ for the colour of the flowers.
 
graveolens
From the Latin ‘grave’, ‘heavy, oppressive, burdensome’ and ‘olens’, ‘smell’.

Common Names and Synonyms

rue, witchbane, herb of grace, garden rue, German rue, herbygrass, mother of the herbs, ruta

How Poisonous, How Harmful?

Contains rutine, a glycoside, furocoumarins, alkaloids, tannin and essential oils. Furocoumarins are responsible for photosensitization, hepatotoxicity and nephrotoxicity.

Ingestion causes vomiting, diarrhoea, epigastric pain, acute gastroenteritis hepatic and renal impairment. Seizures may be observed. Death can occur due to liver failure. In women, uterine haemorrhage and abortion may occur. But there is nothing about the plant which encourages ingestion.

Burn caused by rubbing rue into the skin

The burn caused by exposure to sun after
rubbing rue onto the skin

Dermatitis due to photosensitization results from contact with the furocoumarins. There is some dispute as to how that contact can be achieved. There are those who say that simply being near a rue may cause photosensitization but most of the recorded incidents relate to rue being rubbed onto the skin causing the plant material to break down and release its furocoumarins.

My own experience accords with the view that the plant material must be damaged to release its ingredients. Brushing my hand through a clump of the growing plant produced no ill effects which accords with the gardeners' experience of never wearing gloves when working with rue, but scrunching up some leaves and rubbing them on a small area of the back of the hand resulted in a slightly painful burn appearing a couple of days later. But, see under 'Incidents'.

Sources - The Internet

It is often said that the Internet is a very useful tool. Well, a chainsaw is a very useful tool but it can be enormous harmful if it isn’t used properly.  Though my initial research, in 2003/4, was mostly done on the Internet, it soon became clear that many pages which claimed to be definitive were far from it.

As a result I began investing in the books which were often cited as the source of the information presented and now have an extensive library including most of the most famous ‘herbals’ from the last 2000 years and more.

But, the Internet remains a useful tool, especially for looking into the stories offered as fact by visitors to the Alnwick Garden Poison Garden.

Where information from websites is used on this site it is always the result of researching more than one site and comparing the ‘facts’ presented.

Incidents

A professional gardener was weeding between a number of rue plants with bare arms and hands, as she had done many times before. No damage was done to the rue itself. The next day was especially sunny and by the afternoon her inner arms and parts of the backs of her hands were red and sore. Blistering then occurred and took a number of weeks to heal. It may be that the significant factor was the very bright sun on the day after contact. It could also be that the plants had produced an unusually large concentration of furocoumarins that season. See the Heracleum mantegazzianum, giant hogweed, page for the possible explanation.

This particular incident suggests that the effects of contact with the intact plant are unpredictable making it, if anything, more of a problem than one whose effects are consistent.

A two year old boy was reported to have suffered burns after simply playing near a rue bush. The fact that the burns were confined to his fingers and around his mouth suggests that he may have been crushing the leaves and mouthing them as young children do.

Almost all reported incidents centre around the use of rue as a mosquito repellent. Burns are, often, seen in striations around the neck.

A case was reported in 1999 where Ruta graveolens caused skin problems for someone who had applied it to safeguard themselves from 'evil spirits'.

Folklore and Facts

In folklore, it was used to keep various unpleasant things out of the house. It was hung in doors and windows to prevent evil spirits from entering the house and worn on the belt to keep witches away.

Juice from a crushed stem spread on a wall around a doorway or window frame would keep fleas out of the house. It may be that this belief led to the idea that rue could be used as a mosquito repellent. There are, certainly, a number of internet sites offering repellent creams said to contain essence of rue and a few other sites even go so far as to suggest rubbing the plant itself onto children.

John Gerard says that burning rue will keep serpents away, this use being confirmed by the fact that a weasel will eat rue before it fights a serpent.