Plants directly linked to participants
Dandelion (
Taraxacum officinale) is mentioned three times, by two participants. The white sap from the stem is recommended for external use on warts, and the roots boiled in water can be taken internally for anaemia. It is also one of the most highly cited species among all the TMK entries examined (4.2% of all ‘plant mentions’), and it is documented as a treatment for gastrointestinal and musculoskeletal conditions (Additional files
1 and
2).
T. officinale is abundant throughout Ireland, and the literature supports its medicinal use [
24,
35,
40‐
43]. There is extensive evidence of the global use of this medicinal species throughout history, e.g. in tenth- and eleventh-century Arabian medicine [
44]; in the sixteenth century, the German physician and botanist Leonhard Fuchs documented its use for gout, diarrhoea, blister, spleen and liver complaints [
45]. In 1653, Culpeper also recommended the roots and leaves for the liver and spleen. Its use has also been recorded in North America, China, Turkey and Mexico [
45]. The European Medicine Agency recognises
T. officinale root and herb, based on ‘well-established use’ as a treatment for digestive and urinary complaints [
46]. The majority of research conducted on
T. officinale has focused on the leaves, roots and flowers [
44]. Huber et al. recently identified phenolic inositol esters, triterpene acetates and the sesquiterpene lactone taraxinic acid β-
d-glucopyranosyl ester in the root latex [
47]. The phytochemical composition of
T. officinale and the pharmacological properties of its metabolites including the antimicrobial and anti-inflammatory effects of its sesquiterpene lactones, the reduction in cholesterol absorption by its phytosterols and the presence of immunomodulatory flavonoids and effects of coumarins on cardiovascular disease [
45,
48], would support the reported use in Ireland as a tonic. In 1998, Rudenskaya et al. [
49] identified serine protease activity in the latex of
T. officinale roots. Serine protease modulators in the sap may be linked to the traditional use of
T. officinale in the treatment of warts, although further research is required on stem sap [
50].
Comfrey (
Symphytum officinale) is the only plant that directly correlates from the oral to a participant’s written entry in the SMC. P9’s oral and archival entries recommend external application of an ointment made from the root of the plant to treat burns and sores.
S. officinale is also one of the most highly cited plant species overall (2.1% of all ‘plant mentions’). The root is documented as a treatment for burns and sores in both humans and animals and the plant is recommended as feed for pigs (Tables
2 and
3). These entries correlate with previous accounts of external dermatological and fodder use in Ireland from Moloney [
40], Allen and Hatfield [
24] and Wyse Jackson [
35]. Pliny the Elder’s (23–79 AD) encyclopaedia
Natural Historia recommended the root as a treatment for bruises and sprains and it is similarly cited in Dioscorides’
Materia Medica (50–70 AD) [
51] In 1653, Culpeper added to its indications to include it as a treatment for rheumatism and gout and stated the leaves could be used, although they are not as effective as the roots [
52]. In more recent times, the European Committee on Herbal Medicinal Products (HPMC) has approved the use of
Symphytum officinale L., root for the treatment of ‘bruises and sprains’, based on ‘well-established use’ [
53] The molecular mechanism of action of
S. officinale root has not been completely elucidated. However, allantoin and rosmarinic acid are the most likely bioactive compounds contributing to dermatological healing actions [
54]. Allantoin increases the smoothness of the skin, promotes cell proliferation and wound healing by stimulating the metabolic process in the subcutaneous tissue and stimulating cell growth, resulting in epithelialisation and a protective effect on the skin. Rosmarinic acid possesses an anti-inflammatory action among others [
55].
Table 3
Participant recollections
P1 | – | Father | Once off | No | Yes | Yes | Positive |
P2 | No | Neighbours and parents | One term | Yes | – | No | Positive |
P3 | No | Mrs. Kenny | One year | Yes | – | No—but his daughter was present and said yes | Neutral |
P4 | Yes | Father and neighbours | More than a once off, for a while | No | Yes | No | Positive |
P5 | – | Grandmother and neighbours | – | No | Yes | Yes | Does not recall |
P6 | – | Neighbours | A long time but less than a year | No | Yes | Yes—informed by her daughter | Positive |
P7 | Yes | Grandparents, parents, and people in the community | Every night for a month | No | Yes | No | Positive |
P8 | Yes | Grandmother and father | Two years | Yes | – | Did not say | Positive |
P9 | – | Old people living in the village | A year or two—weekly | Yes | – | No | Positive |
P10 | – | Father | On and off | No | No | No | Positive |
P11 | – | Father and neighbours that visited the house | – | Yes | – | No | Positive |
Dock (
Rumex species) leaf is mentioned orally by two of the participants as a treatment for a sting from a ‘nettle’ (
Urtica diocia L.). Within the overall data, the
Rumex spp. is cited eight further times (5.2% of all ‘plant mentions’). All the entries recommend the same treatment for a sting, although one suggests ‘chewing the leaf’ before applying. The entries cite a range of vernacular names to describe this species, including: ‘dock’, ‘docken’, ‘capog’, ‘cappoc’ and ‘copog’. There are a number of different
Rumex species in Ireland referred to as ‘dock’. However,
Rumex obtusifolius is widely known for the ability to ease the sting of a nettle [
35]. The irritation by a nettle sting is considered to be both biochemical and mechanical. The stem and the underside of the leaves of the
U. diocia are covered in small spicule-type hairs. The biochemical reaction is believed to be the result of formic acid, histamine, serotonin and acetylcholine that is found in the hairs and nettle fluid [
56]. The mechanical reaction is believed to be the impalement of spicules into the skin [
57].
R. obtusifolius leaf contains the flavonoids procyanidin B1, B2, B3, B7 and gallate [
58] and has demonstrated antioxidant and antimicrobial actions [
59].
Rumex spp
. is indigenous to Europe.
R. obtusifolius and has been introduced to many other parts of the world, including: Africa, North and South America [
60].
Potato (
Solanum tuberosum) is renowned as the ‘archetypal Irish vegetable’.
S. tuberosum is a domesticated hybrid plant that was introduced to Europe and Ireland from South America in the sixteenth century. It has had a profound impact on Irish culture, landscape, history and economy [
35]. One participant described how to boil and mash a potato and place around one’s neck to treat a sore throat. Another participant’s entry in the SMC describes how one should ‘rub a potato on a wart’ for a number of consecutive days. There are a total of six entries (3.1% of all ‘plant’ mentions) that recommend
S. tuberosum for dermatological, musculoskeletal and respiratory complaints (Additional files
1 and
2). The entries include external applications of both raw and heated
S. tuberosum. Similar historical medicinal uses have been documented in Ireland, England, Wales and North America [
5,
61,
62]. Glycoalkaloids present in the
Solanum species have demonstrated antifungal, anti-allergic, antipyretic, anti-inflammatory, hyperglycaemic, antibiotic and anti-carcinogenic properties [
63,
64]. In addition, α-solanine, α-solamargine and α-chaconine have shown antifungal and cytotoxicity activity [
65,
66].
Carrageen moss (
Chondrus crispus) is the only sea plant documented in this study. Sea plants have been used in Ireland for centuries, as a food, fodder, soil fertiliser and medicine, and they are considered to be especially valuable for their high iodine and mineral content [
35]. P7’s description of her mother making a drink with
C. crispus to treat a chronic cough corresponds with previous reports from Moloney [
40], Jude [
67], Logan [
42], van Wyk and Wink [
68], Allen and Hatfield [
24], Dolan [
5] and Pina et al. [
69].
C. crispus grows abundantly along the rocky coasts of the north Atlantic and north Pacific oceans [
69]. The mucilage present in this plant is believed to be responsible for soothing and anti-inflammatory properties that help alleviate respiratory conditions [
70]. Various homemade drinks using
C. crispus are still widely used today in Ireland for bronchial conditions [
71].
Oats (
Avena sativa) have been grown in Ireland for centuries as a food crop for both humans and animals [
35]. One participant recalled an oatenmeal paste that was made to treat a boil, and an entry in the SMC details how oatgrass is a treatment for a ‘skinned foot’ on a horse. This external application of
A. sativa correlates with a long history, since Roman times, of being used worldwide, as a treatment for a range of skin conditions [
60‐
62]. ‘Colloidal oatmeal’ is a commercially available topical oat product that has been available since the 1940s. Chemical polymorphism is attributed to its ability to protect and sooth the skin [
72].
A. sativa also possesses different types of phenols which exert an antioxidant and anti-inflammatory activity [
73]. Wound healing and antioxidant activity demonstrated by
A. sativa has been linked to the presence of avenanthramides, flavonoid-type compounds as well as vitamin E and phytic acid [
74].
Meadowsweet (
Filipendula ulmaria) is suggested for ‘stomach problems’ by one of the participants. This plant is native throughout most of Europe and western Asia and has been successfully introduced and naturalised to North America [
75].
F. ulmaria was one of three plants considered to be most sacred by the Druids [
70], and it has a long history of use in Europe as an anti-inflammatory, analgesic, diuretic and anti-rheumatic [
35,
68,
70,
76]. The seventeenth century book
The Complete Herbal recommends using the roots of the plant ‘made into a powder, and mixed with honey in the form of an electuary, doth much help them whose stomachs are swollen, dissolving and breaking the wind which was the cause thereof…’ [
52]. However, use of the herb and flower are most frequently cited, and the European Medicine Agency has accepted it be sold as a ‘Traditional medicinal product for the supportive treatment of common cold, for the relief of minor articular pain’ based on ‘well-established use’ [
76]. Both
F. ulmaria aerial parts and roots have demonstrated anti-inflammatory activity in vitro and in vivo; although, the aerial parts exhibited a higher level of activity [
77]. Salicylic acid and its derivatives are linked to its anti-inflammatory activity [
77,
78].
There is one entry from P9 in the SMC that recommends St. Patrick’s Cabbage (
Saxifraga spathularis) for ‘a sore lip or boil’. Five additional entries (3.1% of all ‘plant mentions’) suggest St. Patricks Cabbage for similar dermatological conditions (Additional files
1 and
2). Interestingly, there is no evidence of this plant being used medicinally. However, all the entries are from two schools in the same locality of County Mayo, so there is a possibility that the vernacular name is referring to an alternative plant or it is a local practice.
One participant recalled Red Rose (
Rosa species) as a treatment for the eyes. Ireland is home to a wide variety of wild rose species. There are at least ten native roses known with many hybrids, thus identification is difficult. Many of the rose varieties in Ireland produce rosehips (fruits). These were a significant wild fruit in ancient Ireland and were often used to make jam, jelly, syrup, pie filling and wine [
35]. Culpeper recommended a decoction of ‘red roses’ made with wine as a treatment for headache and pain in the eyes, ears, throat and gums and another treatment of rose leaves in a mixture with ‘beans’, ‘frankincense and the white of an egg’ to alleviate swollen eyes [
52]. There have not been any specific studies into the use of
Rosa spp. for eye conditions. However, the significant content of bioactive compounds present in rosehips is known to have a high level of antioxidant, antimicrobial, antifungal and anti-inflammatory activity [
79]. These actions are specifically linked to polyphenols, vitamins C, E, B and carotenoids found in this species [
35,
68,
79].
Castor oil (
Ricinus communis) was orally mentioned by one participant as a treatment. However, they did not state for what condition. It is one of the most highly cited plants overall (2.6% of all ‘plant entries’) and includes three entries in the SC that recommend a mixture of castor oil and marigold to treat a burn and one entry that recommends a mixture of sulphur and castor oil to treat sourpock in cattle. The oil is obtained by pressing the seeds of the plant
R. communis. The plant is believed to be native to eastern China and is now cultivated in hot climates around the world, specifically India and southern Asia. It has a long history of use, and in Roman times, it was known as the ‘Palma Christi’, as the leaves were thought to resemble the palm of Christ
. The oil made from
R. communis was traditionally taken internally as a laxative and purgative although this is no longer recommended due to its toxicity [
80]. In the nineteenth century, a number of oils, including Castor oil, were recommended as the first aid for burns. At the time, the oils were suggested for two reasons: their ability to exclude air from the burn and because of their accessibility, quick application was possible [
81,
82]. However, antioxidant activity has been demonstrated by methyl ricinoleate, ricinoleic acid, 12-octadecadienoic acid and methyl ester that are found in the seeds [
80,
83] and the astringent and antimicrobial actions of tannins, flavonoids, triterpenoids and sesquiterpenes also found in the seeds provide wound healing abilities, by promoting wound contraction and increasing the rate of epithelialisation [
80,
84].
Celery (
Apium graveolens) is also one of the most highly cited plants. It is documented six times (3.1% of all ‘plant mentions’) for the treatment of rheumatism. The entries include recommendations to ‘boil the celery seed and drink’, ‘make a drink from celery’ and ‘eat celery’ (Additional files
1 and
2). It is found throughout Europe and in temperate and sub-tropical parts of Africa and Asia [
85]. It is widely documented as used for rheumatic conditions, in Ireland and globally [
24,
35,
86]. The stems are consumed worldwide as a food, and the leaves, seeds and essential oil are used medicinally. Its value as a traditional medicine is attributed to the presence of carbohydrates; flavonoids; alkaloids; and steroids; the compounds limonene, selinene, frocoumarin glycosides and vitamins A and C [
85]. It is suggested that the medicinal effect of the seed on rheumatic conditions is due to its diuretic action [
87].
Chickweed (
Stellaria media) is an extremely common plant found throughout Ireland. There are four entries in total (2.1% of all ‘plant mentions’) recommending its use for dermatological and respiratory conditions (Additional files
1 and
2). The plant is also found throughout Europe and North America [
88]. It has a history of treating a range of conditions including: skin diseases, burns and bruises, inflammation of the digestive, renal and respiratory tract, and rheumatism and joint diseases [
68,
88‐
92]. In Irish mythology, the Celtic God Dian Cécht is believed to have recommended a combination of ‘chickweed, hazel buds, dandelions and wood sorrel to be boiled with oatmeal and taken in the morning and evening’ to treat ‘colds, phlegm, sore throat and the presence of evil things in the body, such as worms’ [
93]. Culpeper also recommended the external application for a variety of ‘hot’ inflammatory conditions [
52]. It is most commonly known as an external treatment for cuts, wounds, irritation and inflammation, as well as an internal remedy for rheumatism, respiratory complaints and jaundice [
24,
35,
68,
87]. Saponin glycosides, coumarins and hydroxycoumaris, flavonoids, carboxylic acids, triterpenoids and vitamin C present in
S. media contribute to anti-inflammatory action [
88].
One of the participants recalled ivy (
Hedera helix) leaves being used for open sores, and two further entries in the SMC (1.6% of all ‘plant mentions’) recommend it as a treatment for corns (Additional files
1 and
2). This corresponds with accounts listed by Culpeper [
52], Wyse Jackson [
35] from Moloney [
40], K’Eogh [
94], MacMahon [
95] and Allen and Hatfield [
24].
Hedera fossils have been recorded in Korea and Europe from approximately 5.8 million years ago, and
H. helix is reported as used medicinally since Greek and Roman times. In present times,
H. helix folium is indicated as an expectorant in the case of productive cough, based on ‘well-established use’ by the European Medicine Agency [
96], and it is most commonly used in Germany [
97]. The chemical components flavonoid rutin, quercetin, kaempferol and apigenin have demonstrated anti-inflammatory, antioxidant and vasoprotective properties. In addition, alpha-hederin, hederacoside B and C and hederagenin, triterpenoid saponins are attributed to the activity of the plant [
98].
Tea (
Camellia sinensis) is Ireland’s most popular and widely consumed beverage. One of the participants recalled a cold tea compress being used, but did not specify for what condition, and there are ten more entries in the SMC (5.8% of all ‘plant mentions’) recommending tea. These include using tea as a treatment for headaches and to bathe sore eyes with cold tea. One interesting treatment documented recommends one to ‘go to a wedding and drink the tea left by the bride and groom’ to cure whooping cough.
C. sinensis origins are Asian. The earliest reference to tea goes back to more than 2500 years in China. Black tea arrived in Ireland in the early 1800s as an expensive and luxurious beverage for the upper and middle classes and later spread to become a common and popular drink for the rural and lower classes in the mid-1800s [
35]. Similar reports of medicinal are documented in India, Kenya and Guatemala [
99]. The chemical components of
C. sinensis include polyphenols (catechins and flavonoids), alkaloids (caffeine, theobromine, theophylline, etc.), volatile oils and primary metabolites polysaccharides, amino acids and lipids. In order to produce black tea, the
C. sinensis leaves undergo fermentation, resulting in an increased level of flavonoids and more concentrated amount of caffeine. Catechins and flavonoid compounds are reported to have antioxidant and antimicrobial properties, caffeine is linked to a diuretic effect and the astringent properties of tannis are believed to alleviate gastrointestinal conditions [
100].
One participant recalled in her interview how an onion (
Allium cepa) should be heated ‘on the fire and then [pressed] against the ear’ to treat an earache. One of the entries in the SMC corresponds with this, and two further entries recommend the juice of an onion for a wasp sting (2.1% of all ‘plant entries’) (Additional files
1 and
2). Ethnomedicinal use in Ireland corresponds with previous reports by Dolan [
5] and Allen and Hatfield [
24]. The
Allium species was one of the first cultivated plant species used for culinary and medicinal purposes. It has been used medicinally worldwide for centuries. Culpeper [
52] states ‘the juice of onions is good for either scalding or burning by the fire…and dropped in the ears, eases pains and noise in them’. It is described as a traditional remedy for a variety of respiratory ailments, bacterial infections, dysentery, ulcer wounds, scars, keloids, pain and swelling after insect stings [
101].
A. cepa is reported to possess a range of actions, including anti-inflammatory and antioxidant [
102] anti-genotoxic and anti-proliferative [
103]. It is a rich source of phytonutrients, containing phenolic compounds such as flavonoids, saponins and sulphur compounds [
104].