Dioscorides lists over a dozen external uses of rue. The herb infused into olive oil by cooking and applied to the abdomen helps inflations of the colon downwards and of the uterus, while the herb ground up with honey and applied to the perineum, ‘from the genitalia to the anus’, relieves uterine suffocation. A similar application is made to joints to relieve pain, while mixed with figs it disperses oedema. As a plaster with barley groats, it assuages severe eye pains and in combination with rose ointment and vinegar it is rubbed onto the head in cases of headache. Ground and inserted into the nostrils, it can stop nosebleeds; plastered on with the leaves of sweet bay, it helps inflammation of the testicles or with a cerate (wax) of myrtle it remedies their pustules. Rubbed on with salt and pepper, it treats dull-white leprosy, which is either vitiligo or psoriasis, and both raised and flat warts. Applied with honey and alum it is good for lichen-like eruptions of the skin. The fresh juice, warmed in a pomegranate shell and instilled, combats earache or mixed with the juice of fennel and honey then smeared on is a remedy for dim-sightedness. Another mixture with vinegar, white lead and rose ointment treats erysipelas, shingles and scurf. When a fresh leaf or two are chewed, it stops the smell and pungency of garlic and onions.
Pliny too records the majority of these uses, in some cases with the same ingredients, suggesting a common source. The herbal of pseudo-Apuleius, in a substantial entry for rue, reproduces fewer than half of them. For dimness of sight Pliny proposes the milk of a woman who has just borne a male child as an alternative ingredient to honey for the application of rue, or simply touching the corners of the eyes with a little of the juice. Engravers and painters, he adds, eat rue with bread or cress to preserve their sight. Rue with barley treats inflamed eyes, and with bay inflammation of the testicles. Apuleius requires the leaves and flowers of rue mixed with wine and applied to the eyes for mistiness and ulceration while restating Pliny’s poultice with barley for inflammations, for which the pounded root may also be used. The fresh herb cooked in oil and mixed with wax as a cerate ‘for the groin’ copies the advice of Dioscorides for inflammation and swelling of the testicles but without the addition of myrtle. Pliny replaces the rose ointment in Dioscorides’ mixture for headaches with rose oil, but if the headaches are chronic, he continues, barley flour should be used instead of rose oil. The juice of rue in vinegar is poured over the head in cases of phrenitis, or with the addition of wild thyme and bay, the liquid is rubbed into the head and neck. Apuleius requires the herb to be mixed with vinegar and rose oil and poured on the head for all head pains. Pliny states that injections of rue decocted in wine with hyssop Hyssopus officinalis are made for nosebleeds, and of the juice for earache. Honey and wine, or oil of rose or bay are added for hardness of hearing and tinnitus. Apuleius wants the herb itself inserted into the nose for bleeding but gives no treatment for ear pains. Applications to the abdomen for heartburn and severe colic are taken from Diodes, a physician of the 4th century BC, and involve mixing rue, vinegar and honey into barley meal, and for the latter pains boiling it in oil and applying the liquid on pieces of fleece. The simpler solution of Apuleius is to hold the herb in position on the skin over the organ. Treatment of skin eruptions and erysipelas in Pliny are the same as in Dioscorides, while that for vitiligo/psoriasis, warts, scrofula and the like require the addition of nightshade (undefined), lard and beef suet. Only the ‘sacred fire’ or erysipelas is mentioned in Apuleius, for which rue mixed with oil and vinegar is rubbed on.
Pliny offers other mixtures for external uses not mentioned by Dioscorides: the leaves boiled in oil for frostbite; carbuncles resolved by rue in vinegar, also cited in Apuleius; the mixture for nosebleeds as a mouthwash; a decoction of the plant applied to swollen breasts; an ointment of wild rue amazingly to resolve hernias; broken limbs healed by a wax plaster of rue seed; the root applied to bloodshot eyes and to heal scars and clear spots; finally, and despite it being a very heating herb which may be expected to open the pores of the skin, a bunch of rue boiled in rose oil with 1 oz of aloes checks the perspiration of those who have rubbed themselves with it. This formula is recommended for heartburn in Apuleius. The Myddfai physicians support Pliny’s contention by recommending pounded rue rubbed into the skin as ‘excellent for those hectic perspirations which so weaken a man’.
These external uses are handed down, in total or in part, through the Renaissance authors. They are partially reported in Ibn Sina, who adds baldness to the list of indications. Serapio only quotes Dioscorides. The medieval authors only report a few of the classical uses, but notably those for dim-sightedness and inflammation of the eyes. The Old English Herbarium reproduces fairly exactly the formulae for topical use in Apuleius for nosebleeds, eye pain and swelling and headache, but omits external applications for abdominal swelling. The Red Book of the Myddfai physicians lists thigh pains and bites of vipers, and the later 18th century prescriptions for topical use covers parasites in the skin, carbuncles, whitlows, cancer, arthritis and other aches, eye pain, sore throat with fever, a painful mouth and snake bites. The Salernitan herbal suggests heating rue and sage Salvia officinalis on a tile then apply to contusions, while Dodoens describes bruising among the indications. Bauhin advises the distilled water of rue for nasal polyps and to purge the head. Macer and the Arabic authors include external applications for headache, repeated many centuries later by Dr Fernie (1897), from whom Grieve obtained the substantial part of her entry for rue. Robinson (1868) cites Professor Herman Boerhaave (1668-1738), a physician famed for his clinical teaching, on rue mixed with wine and salt to stop gangrene, restore vitality to a part, prevent suppuration and heal wounds. Fernie also transmits the benefit of rue for the eyes, reminding us that the visual nerve of Adam was purged by Milton’s angel with ‘Euphrasy [eyebright Euphrasia officinalis] and Rue’. He cites an old rhyme: ‘Noble is Rue! It makes the sight of eyes both sharp and clear. With help of Rue, oh blear-eyed man! Thou shalt see far and near’. Bauhin reproduces the full Latin saying: ‘nobilis est ruta qui alumina reddit acuta: auxilio rutae, vir lippe vedebis acute’. In addition to eye problems, Fernie proposes another external use, of compresses saturated with a strong decoction of the plant applied to the chest beneficially for chronic bronchitis.
We have seen weakness of the eyes listed among the unverified indications of rue in the Commission E monograph. Bartram also includes this indication, while luliette de Bairacli Levy (1966) offers seemingly her own preparation ‘for eye ailments, including treatment of cataract’: infuse a tablespoon of rue flowers for 3 days in a cup of water to which is added a teaspoon of white wine, the preparation to sit in a shallow dish in sunlight, or slowly heated in an oven with the door open if no sunshine is available. The eyes are then bathed several times daily with this water. A similarly gentle extraction is mentioned in Apuleius, where morning dew is collected from the plant in a small vessel and mixed with vinegar for bathing the eyes. Levy is well aware of the potency of rue and advises small doses. For internal use she suggests the ratio of a small teaspoon to a glass of water, as a ‘standard brew’ with a dose of only 2 tablespoons of the liquid twice daily. On the other hand, she seems familiar with the need for a substantially larger dose as an antidote to snake bite ‘suck out the poison or cut out with the point of a sharp knife, in the usual way. Infuse 2 oz of fresh rue in a pint of beer, drink this and apply some frequently to the bitten area’. This dose is similar to that in the case of poisoning in the elderly Taiwanese woman but Levy’s preparation is an infusion not a decoction and certainly not intended to be given to a person with cardiac hypertrophy and on medication for the problem.
It is apparent from the external applications, old and new, that fresh rue is used. Pliny specified that rue juice is extracted by pounding the plant with a sprinkling of water and the juice must be kept in a copper box. Are the levels of essential oil obtained sufficient to preserve the juice in this way? Conversely, aqueous infusions of the fresh plant will not extract as efficiently these same oils, thus rendering the resulting liquid for internal administration milder and potentially less toxic. The specification of the Commission E monograph for the dried leaves of rue has the same intention, since the quantity of volatile oils will be reduced in the drying process, but it is not the case that the Ancients did not appreciate the dangers of rue. We have already heard the opinion of Gargilius Martialis, and earlier Pliny too affirmed the risks to pregnant women of consuming rue in their diet, ‘for I find that the foetus is killed by it’. It seems that the Romans, much more than the Greeks, used rue as a condiment. Fresh and dried rue were employed in the form of a bouquet garni or a sprig used to stir a sauce in the recipes of Apicius, while bunches of rue were pickled in brine for use at the table. ‘It is prudent to assume that in his recipes rue was meant to be used invariably with moderation, even when this was not specifically recommended’.
Dioscorides does not warn that pregnant women should not eat rue, but states that it is emmenogogue. This action has passed down to the present day, in statements such as Fuch’s ‘if a pregnant woman drinks the juice, she will abort’ and Turner’s citing of Seth ‘the juice of this herb is evil for women with child’. It is the only action listed in the British Herbal Pharmacopoeia to yield an indication (atonic amenorrhoea). According to Dioscorides the seed of rue quells the organ of generation, and this linked effect is discussed in herbals down to the 17th century, as, for instance, Pliny’s ‘for spermatorrhoea and frequent amorous dreams’, Galen’s ‘inhibiting the appetite of Venus’, ‘for the flowing of semen’ in Apuleius, Ibn Sina’s ‘dries up the seed, checks its flow and kills lust’, Gerard’s ‘quencheth and drieth up the naturall seed of generation’ and Culpeper’s (1669) ‘consumes the seed, and is an enemie to generation…is nought for women with child’. Hildegard tells us that lack of sexual release is also harmful. She advises that ‘if a man is sometimes stirred up in delight, so that his sperm arrives at the point of emission but has in some way been retained within his body and he has begun to be ill from it’, that he should take a preparation of rue and wormwood Artemesia absinthium in sugar, honey and wine in order to help the body void the ‘noxious mucus’ via urine and stool. Applicable to both sexes is Bauhin’s observation that those who have devoted themselves and are sworn to chastity are greatly helped by a daily dose of 1 oz of the seeds in drink. Riddle (1991) interprets the statements in Soranus’ Gynaecology, another 1st century AD text, on the use of rue as a vaginal suppository to imply an antifertility effect through contraceptive and abortifacient means. Both he and Mills & Bone (2000) identify the use of euphemistic language: Riddle says that Pliny’s citation from Hippocrates that rue removes ‘the foetus that has died before delivery’ is a common circumlocution for abortion, while Mills & Bone argue that emmenogogues were used to ‘bring on the menses’ when they were delayed by pregnancy. Thus Dioscorides’ words may provide sufficient warning to women of rue’s power in this respect.
Dioscorides is more specific on other aspects of rue’s potential toxicity Both garden and wild varieties burn and ulcerate. He points out that ‘the rue that grows on mountains and the wild is harsher than the cultivated and unfit to eat’, that ‘eating much wild rue is fatal: gathered for pickling when in bloom, it does redden and puff up the skin with itching and with a violent rash. People must thus harvest it after they have anointed their face and hands’. So, here is evidence of ancient knowledge of rue’s ability to cause a contact dermatitis, and since rue flowers in the summer months and in sunny climates, it would have been difficult in former times to distinguish this from a phototoxic dermatitis. Furthermore, for internal consumption, the question of dosage is again crucial. Dioscorides balances his statement that eating much wild rue is fatal with the notion, of which he is sceptical, that ingestion of any amount is immediately followed by death They say.. .that the rue that grows in Macedonia by the river Haliacmon is fatal when eaten; this place is mountainous and full of vipers’. Pliny states that an overdose of the juice, which is normally taken in wine in doses of one acetabulum (around 60 mL), is poisonous, especially from the Macedonian rue specified by Dioscorides. ‘Strangely enough, it is neutralized by the juice of hemlock; so there are actually poisons of poisons, and hemlock juice is good for the hands and face of those who gather rue’.
Pelikan gives us a modern take on rue’s ability to combat poisons and infectious diseases. He contrasts abnormal astral forces operating in plants to render them poisonous, with rue’s ability to assimilate these forces through the dominance of a cosmic T-like nature. This is apparent in its formation of volatile oils and expression of a warmth principle, as also seen among the healing aromatic plants of the Labiate family. However, this warmth principle and expression through volatile oil production is particularly strong in rue. In order for rue to be tolerated, the human T-impulses within the patient must also be strong. In this way rue protects the person from outside influences like infectious disease and poison. The strong fire and light forces within rue link both to its ability to treat the eyes and its power to cause blistering of the skin on contact.