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(Hemp family)


• Medicinal / Folk-medicinal aspects: Preparations for treating sore eyes have been used in traditional medicine in both Central Africa and Central America. Some other uses, mostly for skin infections and wound healing have been recorded from in and around northern India; and for pediculosis in North Africa. •
• Adverse effects: Cannabis sativa L. and Humulus lupulus L. are both documented as causes of occupational allergic contact dermatitis. The responsible allergens have not been unequivocally identified. Mechanical irritation of the skin and eyes caused by rough hairs present on many species and mechanical injury caused by the spines on other species may also occur. Timber derived from certain Celtis L. species has been reported to produce skin reactions in woodworkers. •
• Veterinary aspects: Dermatitis and photodermatitis in cattle has been ascribed to a member of the genus Trema Lour. in Australia. •

Once included in the Moraceae and formerly known as the Cannabidaceae or Cannabinaceae, this family was until recently considered to comprise just 4 species in 2 genera, namely Cannabis L. and Humulus L. The transfer into this family by the Angiosperm Phylogeny Group (2003) of a number of genera formerly included in the Ulmaceae or Celtidaceae has now expanded the Cannabaceae to 9 genera and about 90 species (Mabberley 2017).

Two of the species are of unusual economic importance. Cannabis sativa L. provides the fibre hemp from its stems, cannabis resin from its flowering tops, and bird seed and fishing bait from its seeds. The plant is cultivated mainly (and illicitly) for its resin, which has mood and perception altering properties. Humulus lupulus L., a climbing herb, is also extensively cultivated. It provides hops. These are used both in the brewing industry and at home in the production of beer and similar alcoholic beverages. Thus, a large number of people throughout tropical and temperate regions are likely to come into contact with the plants or their products.

Some Celtis L. species are known to horticulture, being grown as ornamental trees (Hunt 1968/70). Several provide useful timber (Irvine 1961).

Humulus lupulus L. is included in a number of proprietary herbal sedative preparations (Stuart 1979, Wren 1988, Reynolds 1996). It may also be used in a smoke or tea (Siegel 1976).

Cannabis sativa L.
[syns Cannabis indica Lam., Cannabis ruderalis Janisch., etc.]
Indian Hemp, True Hemp, Marihuana, Marijuana

Although it is commonly believed that the morphological differences seen in different populations of the cannabis plant are indicative of the existence of two or even three distinct species (Cannabis indica Lam., Cannabis ruderalis Janisch., Cannabis sativa L.) or subspecies, only one rather variable species is now accepted. The previously recognised more northerly cultivated subspecies Cannabis sativa subsp. sativa (loosely, the "Sativa" phenotype) is grown as a source of fibre known as hemp, whilst the more southerly cultivated Cannabis sativa subsp. indica (Lam.) E.Small & Cronquist (loosely, the "Indica" phenotype) yields a psychotropic drug which in its various forms is known as churrus, gunjah, bhang, hashish, marihuana, pot, dagga, kif, etc. (Pereira 1842, Trease & Evans 1966, Mabberley 2017). However, it is now recognised that whilst these phenotypes were originally shaped by natural selection in their respective environments, subsequent domestication has enhanced phytochemical divergence. In a quest to increase the content of the psychoactive component Δ⁹-tetrahydrocannabinol [THC], massive crossbreeding has now obliterated differences between "Sativa" and "Indica" phenotypes, this having been adduced from "DNA barcode" studies (McPartland 2020), creating a multitude of what are now best described as chemotypes, chemovars, or cultivars. Accordingly, due caution needs to be exercised when interpreting the dermatological / medical literature.

Workers who process the plant for its fibre, known as hemp, can develop maceration of the skin from standing in water in the retting basins. The dust from the dried fibre may also cause irritation and pruritus. Secondary infection from scratching, and reactions to the oil used in the process can also occur (Slaviero 1915, Schwartz et al. 1957, Hegyi et al. 1965). Meneghini & Gianotti (1953), Touton (1932), Porias (1922) and Oppenheim (1914) also refer to this topic.

Silverstein & Lessin (1974) found that the chronic use of marihuana did not decrease the capacity of a subject to become sensitised and to develop delayed cutaneous hypersensitivity when challenged with 2,4-dinitrochlorobenzene (DNCB).

Marihuana can be contaminated with herbicides including Agent Orange, phencyclidine, and paraquat, and also with storage fungi belonging to the form-genus Aspergillus Mich., fam. Eurotiaceae (Kagen 1981). In addition to the potential toxicity/pathogenicity associated with inhalation of these materials, they may render the results from patch tests with crude plant material or with simple extracts unreliable.

In traditional Chinese medicine, a preparation of the seeds (Semen Cannabis Sativa; huo ma ren; 火麻仁; Cannabis Fructus; ma zi ren; 麻子仁; da ma; 大麻) is used externally for eruptions, ulcers, favus, wounds, and falling of the hair. The freshly expressed juice from the leaves is also used to stop the hair from falling out and to prevent it from turning grey (Stuart 1911).

[Further information available but not yet included in database]

Celtis L.
Hackberry, Nettle Tree, Sugar Berry

[Information available but not yet included in database]

Celtis ehrenbergiana (Klotzsch) Liebm.
[syns Celtis pallida Torr., Celtis spinosa var. pallida (Torr.) M.C.Johnst., Momisia ehrenbergiana Klotzsch]
Desert Hackberry, Granjeno, Spiny Hackberry

[Information available but not yet included in database]

Celtis iguanaea (Jacq.) Sarg.
[syns Celtis aculeata Sw., Celtis spinosa Ruiz ex Miq., Mertensia iguanaea (Jacq.) Schult., Momisia iguanaea (Jacq.) Rose & Standl., Rhamnus iguanaea Jacq.]
Iguana Hackberry, Desert Hackberry

[Information available but not yet included in database]

Celtis liukiuensis Nakai

[Information available but not yet included in database]

Celtis madagascariensis Sattarian

[Information available but not yet included in database]

Celtis tessmannii Rendle
[syn. Celtis brieyi De Wild.]

[Information available but not yet included in database]

Celtis timorensis Span.
[syn. Celtis cinnamomea Lindl. ex Planch.]

[Information available but not yet included in database]

Chaetachme aristata Planch.
[syns Chaetachme madagascariensis Baker, Chaetachme microcarpa Rendle, Chaetachme serrata Engl.]
Thorny Elm

[Information available but not yet included in database]

Humulus lupulus L.
Hop, Echter Hopfen

Dermatitis from hops has long been recognised (Badham 1834, Danlos 1900, White 1903, Broers 1926, Lewith 1928), and has been attributed to mechanical abrasion by the rough hairs on the climbing stem (Maiden 1918a, Wimmer 1926). Maiden (1918a) suggested also that lupulin, a yellow powdery secretion of the glandular hairs on the scales of the hop cones, may be responsible for the irritation.

Hops in beer were alleged to have caused dermatitis in a bar-tender (Hurst 1942). Respiratory allergy to hops can also occur (O'Donovan 1924, Newmark 1978, Godnic-Cvar 1999).

A 43-year old female who worked in a laboratory carrying out chemical analyses of hops developed conjunctivitis, rhinitis, bronchitis and dermatitis of the face from exposure to airborne hop dust. A patch test with hop dust produced a positive reaction after 2 days, and an intradermal test with an aqueous hop extract produced erythema and a wheal after 5 minutes, suggesting that she had developed both an immediate and a delayed-type hypersensitivity to hops. No tests in controls were reported (Raith & Jäger 1984). Śpiewak & Dutkiewicz (2002) described a case of airborne dermatitis to hops in a 57-year old female farmer who also experienced acute dermatitis of the hands. Prick tests to saline and glycerol extracts of hop leaves and cones were positive; and a glycerol extract of the hop cones produced a positive patch test reaction at 48 h and 72 h. Relapses of her dermatitis occurred upon connubial exposure to hop allergens on her husband, and to hop extract present in an externally-applied beauty cream and in an orally-administered herbal sedative.

Remington et al. (1918) noted that "Fomentations with hops, and cataplasms made by mixing them with some emollient substance, are often beneficial in local pains and tumefactions." This use of hops may have been described originally by Dale (1739) who wrote: "De Lupulo Salictario — Extrinsecus sedat dolores, auxiliatur contusionibus, luxationibus, tumoribus." Pereira (1842) also referred to this use: "Hops have been applied, topically, in the form of fomentation or poultice, as a resolvent or discutient, in painful swellings and tumours."

[Further information available but not yet included in database]

Humulus scandens (Lour.) Merr.
[syn. Humulus japonicus Siebold & Zucc.]
Japanese Hop, Houblon Japonais, Japanischer Hopfen

This is a fast-growing annual twining vine native to the Far East, which has been introduced into North America and Europe [and elsewhere] as an ornamental. However, in certain countries (for example, USA, Hungary, Italy) it has become invasive, threatening natural vegetation on river banks in particular (Balogh & Dancza 2008). It can climb to heights of 3m (10ft) or more with the help of many small hooked prickles that cover the stem, which can cause irritation to bare skin. The leaves are divided into 5–9 lobes with downward pointed prickles and down-curved bracts at their base. The down-curved bracts and sharp prickles are distinguishing characteristics of this plant (Heise 2015). Stuart (1911) noted that the wild hop of China and Japan is covered with fine prickles which chafe the skin when they come into contact with it.

Humulus Japonicus Extract & Humulus Japonicus Flower/Leaf/Stem Extract [INCI] are recognised cosmetic product ingredients purported, respectively, to have skin protecting and skin conditioning properties (Standing Committee on Cosmetic Products 2019, CosIng 2023/4).

Trema Lour.

[Information available but not yet included in database]

Trema asperum Blume
[syns Celtis aspera Brongn., Trema tomentosa H.Hara var. asperum Hewson]
Native Peach, Poison Peach, Peach-Leaved Poison Bush

Referring to Trema aspera, Hurst (1942), citing Ewart & Tovey (1909), noted that the leaves [upon ingestion ?] act as a mechanical irritant to animals or cause impaction of the stomach owing to the tough nature of the fibre. The plant has also been suspected of producing photosensitisation in cattle (Hurst 1942), this ostensibly being a secondary manifestation of the liver damage caused by an ingested hepatotoxin, trematoxin, reported from this species by Oelrichs (1968). However, according to Cullen & Stalker (2016), whilst this species has caused severe losses of cattle in Australia, the syndrome is acute, there is no photosensitization, and mildly intoxicated animals may recover completely.

Trema cannabinum Lour.
[syns Celtis microphylla Zipp. ex Blume, Trema carinatum Blume, Trema morifolium Blume, Trema virgatum Blume]
Lesser Trema, Poison Peach

[Information available but not yet included in database]

Trema orientalis Blume
[syns Celtis guineensis Schumach. & Thonn., Celtis orientalis L., Trema bracteolatum Blume, Trema guineense Ficalho]
Charcoal Tree, Gunpowder Tree, Pigeonwood, Rhodesian Elm, Indian Nettle Tree, Poison Peach, Peach Cedar, Woolly Cedar

The leaves of Trema guineensis [sic], the upper surfaces of which are rough, have been used as a substitute for sandpaper (Williamson 1955). Watt & Breyer-Brandwijk (1962) note that handling the tree has sometimes resulted in the development of eczema.


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Richard J. Schmidt

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