The Ericaceae comprises some 3400 species in 107 genera which are of cosmopolitan distribution except in deserts, but scarce Australasia. The family now includes genera previously classified in the families Monotropaceae and Pyrolaceae (Mabberley 1997).
Many species are cultivated, forming highly decorative plants or shrubs. They require lime-free or acidic conditions in which to grow. The fruits of certain species are edible and sought after when in season. The (blue) whortle berry, bilberry, or blaeberry is derived from Vaccinium myrtillus L.; the (red) cow berry or whinberry is derived from Vaccinium vitis-idaea L.; the (red) cranberry is derived from Vaccinium oxycoccos L.
Many members of the family are poisonous to livestock, including certain Ledum L., Leucothoë D.Don, Menziesia Sm., Pieris D.Don, Rhododendron L., and Pernettya Gaudich. species (Lewis & Elvin-Lewis 1977). Certain Kalmia L. and Rhododendron L. species yield poisonous honey (Morton 1964).
Some species of Gaultheria Kalm contain gaultherin which is a glucoxyloside of methyl salicylate. Gaultherin (formerly known as monotropitoside or monotropitin) releases methyl salicylate on mild enzymically induced hydrolysis when the plant material is damaged. Methyl salicylate (oil of wintergreen) is known for its rubefacient properties but may also induce contact sensitivity. Species of Rhododendron L., a genus from which methyl salicylate yielding plants have not been reported, have on occasion been reported to elicit contact dermatitis.
The Songish Indians of the north-western coast of North America rubbed the leaves on areas affected by rheumatism; the Cowichian Indians rubbed them on burns. The Cowichian Indians also used the boiled bark for cuts and wounds (Turner & Bell 1971).
This plant from tropical America has a strong odour of wintergreen (von Reis & Lipp 1982). (See Gaultheria Kalm below).
This species was at one time used as a substitute for Chimaphila umbellata (see below), possessing similar powers (Felter & Lloyd 1898). Schwartz et al. (1947) included this species in a list of irritant plants without making reference to the source of their information.
Chimaphila, prepared from the leaves of this species, was at one time an official drug in the US Pharmacopoeia. An infusion of the plant was used both locally as a wash and internally as a remedy for scrofulous ulcers. The name King's cure was acquired from the high reputation with which this remedy was held (Pereira 1842, Felter & Lloyd 1898).
The fresh leaves, when bruised and applied to the skin, may produce redness, vesication, and desquammation (Pereira 1842, Piffard 1881, White 1887, Felter & Lloyd 1898). Schwartz et al. (1947) included this species in a list of irritant plants without making reference to the source of their information.
Over 500 species are native to Europe, Asia Minor and Africa. The two common European heaths E. cinerea L. and E. tetralix L. cover great areas of moor.
Bell heather briskly applied to skin produced a violent reaction. Ordinary heather (possibly E. tetralix L., the cross-leaved heath) produced no reaction (Low 1924).
Perhaps 200 species are native to regions around the Pacific Ocean. Two species are native to eastern North America and 8 species to Brazil.
The following taxa have been reported to yield, or have an odour of, oil of wintergreen (Towers et al. 1966, Buruah & Dhagat 1976, von Reis & Lipp 1982), suggesting the presence of gaultherin:
The following species have been reported to yield salicylic acid as the major product of hydrolysis of the ethanol extract (Towers et al. 1966), and hence also probably contain gaultherin:
See also Gaultheria procumbens L.
Gaultherin, from which methyl salicylate (oil of wintergreen) may be obtained by mild hydrolysis when the plant material is damaged, has been reported from this species (Yasue & Sasake 1938, Towers et al. 1966). See also Gaultheria procumbens L.
The plant contains gaultherin from which methyl salicylate may be released (Towers et al. 1966). See also Gaultheria procumbens L. von Reis & Lipp (1982) have also noted that this species had an odour of wintergreen.
In traditional medicine, preparations of the leaves have been used externally as a counter-irritant in the treatment of various aches and pains including rheumatism (Hurst 1942, Wren 1975, Stuart 1979). The fruit is edible.
Gaultherin, from which methyl salicylate is released on mild hydrolysis, has been reported to occur in the leaves (Towers et al. 1966). Gaultheria oil or wintergreen oil, which consists almost solely of methyl salicylate, was formerly distilled on a commercial scale from the leaves of this species. This oil has since been replaced by synthetic methyl salicylate (Arctander 1960).
Methyl salicylate is absorbed when applied to intact skin, and may produce symptoms of systemic toxicity. Undiluted, it is a severe irritant to guinea pig skin and eyes. When applied at a concentration as low as 1%, it is a moderate irritant and may elicit necrosis and intradermal and subcutaneous haemorrhage. When applied in a closed patch test at a concentration of 8% in petrolatum, it was found to be non-irritant at 48 hours. A maximisation test with 8% methyl salicylate in petrolatum failed to sensitise any of 27 volunteers (Opdyke 1978).
Methyl salicylate (2% in petrolatum) produced positive patch test reactions in 3 out of 183 eczema patients (Rudner 1977).
Shelley (1964) described a generalised pustular psoriasis in a 6 year old who had chewed teaberry leaves. This was ascribed to an exquisite hypersensitivity to salicylates.
Gaultherin, from which methyl salicylate (oil of wintergreen) may be obtained by mild hydrolysis when the plant material is damaged, has been reported from this species (Towers et al. 1966). See also Gaultheria procumbens L.
The berry is edible. The stiff leaves are a source of minor mechanical injury to bare ankles.
All parts of the plant, including the pollen, are poisonous (Lewis & Elvin-Lewis 1977). The syndrome of poisoning from ingestion of the plant includes cutaneous effects - sweating and tingling sensations (Muenscher 1951).
This plant, held on the skin with shredded undyed cedar bark as a poultice, was strong enough to cause blisters to form on the skin. The blisters were opened with broken mussel shells and smeared with catfish oil (Densmore 1939, Boas 1966, Turner and Bell 1973, Turner 1973).
Gaultherin, otherwise known as monotropitin, from which methyl salicylate may be obtained by mild hydrolysis when the plant material is damaged, has been reported from this species (Bridel 1923). See also Gaultheria procumbens L.
White (1887) received a report that the tree is an acrid poison when handled. The plant was listed as an irritant by Pammel (1911), and by Weber (1937).
In Chinese traditional medicine, the plant material from either species is bruised and applied to wounds to staunch haemorrhage, and is also applied to animal and insect bites. The name Lu Ti Tsao refers to either species (Stuart 1911).
Some 500-600 species are native to northern temperate regions. They form shrubs and small trees and are commonly grown for ornament. Those named rhododendrons usually have leathery, more or less evergreen leaves; the leaves of azaleas are deciduous and usually last only one year.
Cleland (1943) noted a report of dermatitis on the arms from cutting azaleas and rhododendrons. The leaf of an azalea produced a positive patch test reaction in 1 of 87 patients tested (Fregert & Hjorth 1969). Dermatitis from rhododendron was reported by Igumonov (1967).
Agrup & Fregert (1968) reported a case of a woman who was contact sensitive to a variety of this species and to a streptocarpus (Streptocarpus Lindl., fam. Gesneriaceae).
Contact sensitivity to the leaf was observed in one patient (Agrup 1969).
Wren (1975) records that a decoction prepared from the ripe fruit has been used in folk medicine as a wash for wounds, sores and ulcers.