- Cleistanthus collinus Benth. & Hook. f.
This species is a violent gastro-intestinal irritant (Chopra & Badhwar 1940). The leaves or seeds thrown into still streams stupefy fish (Burkill 1935, Uphof 1959). These properties are found in members of the Euphorbiaceae known to contain skin irritant diterpenoid esters.
- Clutia pulchella L.
The juice of this plant produces irritant effects (Watt & Breyer-Brandwijk 1962).
- Cnesmone Blume
- (syn. Cenesmon Gagnepain)
Ten species are found in Assam, southern China, south-eastern Asia, and western Malaysia.
Stinging hairs are known in members of this genus (Wimmer 1926, Thurston & Lersten 1969).
- Cnesmone javanica Blume
- Jelatang Rusa
This species, a slender climber with stinging hairs (Burkill 1935), is strongly hirsute and urticating (Airy Shaw 1975). Smitinand & Scheible (1966) record that all parts of the plant are covered with stinging hairs which cause irritation and pain when they touch the skin. Ridley (1898) and Gimlette (1929) agree that the plant does not sting severely.
- Cnesmone laevis Airy Shaw
- (syn. Tragia laevis Ridley)
This climbing plant of Malaya possesses stinging hairs and is known to produce skin reactions (Airy Shaw 1969, Kochummen 1972). Ridley (1923) and Burkill (1935) noted that the plant does not sting badly.
- Cnesmone laotica Croizat
- (syn. Cenesmon laoticum Gagnepain)
This is an undershrub with stinging hairs (Airy Shaw 1969).
- Cnesmone subpeltata Ridley
This climbing plants possesses irritant hairs and is known to produce skin reactions in Malaya (Kochummen 1972).
- Cnidoscolus Pohl
- Spurge Nettle
This tropical American genus comprises some 75 species of nettles. Cnidoscolus was at one time included within Jatropha L. from which it was separated on the basis of its stinging hairs (Thurston & Lersten 1969).
Stinging hairs have been noted on the following species (von Reis Altschul 1973, Jacobsen 1974, Bailey & Bailey 1976, Morton 1981):
- Cnidoscolus angustidens Torrey
- (syn. Jatropha angustidens Muell. Arg.)
- Cnidoscolus chayamansana McVaugh
- Cnidoscolus cnicodendron Griseb.
- Cnidoscolus multilobus I.M. Johnston
- (syn. Jatropha multiloba Pax)
- Cnidoscolus texanus Small
- (syns Jatropha texana Muell. Arg., Cnidoscolus stimulosus Engelm. & A. Gray)
- Cnidoscolus tubulosus I.M. Johnston
- (syn. Jatropha tubulosa Muell. Arg.)
- Cnidoscolus longipes I.M. Johnston
This species has caustic latex (von Reis Altschul 1973).
- Cnidoscolus stimulosus A. Gray
- (syns Jatropha urens L., Jatropha stimulosa Michaux)
- Tread-Softly, Bull-Nettle, Spurge Nettle, Stinging Spurge
This species, found in dry sandy woods, fields, and sandhills from Florida to Texas and north to Virginia, has stinging bristles (Fernald 1950, Thurston & Lersten 1969). Wimmer (1926) referred to the stinging hairs of "Jatropha stimulata"; Dahlgren & Standley (1944), describing edible and poisonous plants found in the Caribbean region, cautioned that Jatropha urens is thickly covered with stiff hairs which sting severely and cause pain and inflammation, often with numbness lasting a day or more. Hardin & Arena (1974) noted that urticaria can arise from contact with the plant; von Reis Altschul (1973) similarly noted that red welts are produced by the painfully stinging hairs on contact.
- Cnidoscolus urens Arthur
- (syn. Jatropha urens L.)
- Brazilian Stinging Nut
The latex is capable of burning the skin to produce serious sores; the poisonous hairs produce great irritation of the skin which may last for several days (Watt & Breyer-Brandwijk 1962, von Reis & Lipp 1982). Wimmer (1926), Standley (1927), and von Reis Altschul (1973) also refer to the stinging hairs of this species. Lutz (1914) described an extreme reaction following contact with 10 of the stinging hairs on the left hand. This resulted in an increasingly painful swelling of the hand spreading to the arm and subsequently to the other arm and to the face about the eyes and nose. A strong itching sensation was felt over the upper parts of the body; red pimples appeared everywhere. Cardiac and respiratory distress led to unconciousness.
This species is considered to be dangerous to both man and livestock (Lutz 1914).
- Cnidoscolus vitifolius Pohl
- (syn. Jatropha vitifolia Mill.)
von Reis Altschul (1973) records that this species has poisonous juice and stinging hairs.
- Codiaeum A. Juss.
Fifteen species are found in Malaysia, Polynesia, and northern Australia.
The "crotons" commonly grown as house plants are cultivars of Codiaeum variegatum A. Juss. The other species of Codiaeum are very rarely grown.
- Codiaeum variegatum A. Juss.
- (syn. Codiaeum variegatum A. Juss. var pictum Muell. Arg., Codiaeum variegatum Blume, Croton pictus Lodd., Croton variegatus L.)
- Croton, Garden Croton
Notwithstanding the common name of these plants, they should not be confused with members of the genus Croton L.
Different leaf forms and colour variations often appear on the same plant as a result, it is said, of genetic instability. A colourless liquid that bleeds from the broken leaf stem stains white cloth to a brown colour which increases in darkness when the fabric is wetted. These markings have been mistaken for blood stains (Brown 1960a).
The young leaves of certain of the yellow varieties are eaten as flavouring; old leaves irritate the mouth because their acridity increases with age (Brown 1960a). The bark and roots are acrid and cause burning in the mouth if chewed. Although mature leaves may be irritant, the plant is rarely a cause of dermatitis despite much handling of foliage for decoration and of cuttings for propagation (Morton 1962a). Souder (1963) lists this species among spurges that cause an acute dermatitis on contact with their sap or latex; Allen (1943) stated that handling of, or even proximity to, the plant in Panama can produce in many individuals a dermatitis resembling erysipelas.
A positive patch test reaction to the leaf has been observed in one patient by Agrup (1969). A flower grower who had hyperkeratotic eczema localised to the tips of the thumbs and index fingers showed positive patch test reactions to the leaf and stalk of the plant, negative in 5 controls. The sensitiser seemed to be soluble in water but not in alcohol (Tafelkruyer & van Ketel 1976). Hausen & Schulz (1977b), Schmidt & Ølholm Larsen (1977), and van Ketel (1979a) also reported allergic contact dermatitis to the plant in gardeners. Both Hausen & Schulz (1977b) and van Ketel (1979a) reported that guinea pigs could be sensitised to a methanolic extract of the plant, and that the plant was not an irritant. Soejarto et al. (1977) were of the opinion that the Codiaeum of Schmidt & Ølholm Larsen (1977) was in fact a Croton L. species, but this was subsequently refuted (Schmidt & Ølholm Larsen 1978).
- Colliguaja odorifera Molina
This species is said to be irritant (Schwartz et al. 1957).