The Gaultheria species share the common characteristic of producing oil of wintergreen. Wintergreen oil is a pale yellow or pinkish fluid liquid that is strongly aromatic with a sweet woody odor (components: methyl salicylate (approx. 98%), a-pinene, myrcene delta-3-carene, limonene, 3,7-guaiadiene, delta-cadinene that gives such plants a distinctive "medicinal" smell whenever bruised. Salicylate sensitivity is a common adverse reaction to the methyl salicylate in oil of wintergreen; it can produce allergy-like symptoms or asthma. Wintergreen essential oil is obtained by steam distillation of the leaves of the plant following maceration in warm water. Methyl salicylate, the main chemical constituent of the oil, is not present in the plant until formed by enzymatic action from a glycoside within the leaves as they are macerated in warm water. The oil is used topically (diluted) or aromatheraputically for muscle and joint discomfort, arthritis, cellulite, obesity, edema, poor circulation, headache, heart disease, hypertension, rheumatism, tendentious, cramps, inflammation, eczema, hair care, psoriasis, gout, ulcers, broken or bruised bones. It is also used in some perfumery applications and as a flavoring agent for toothpaste, chewing gum and soft drinks, confectionery, in Listerine, and in mint flavorings, but Gaultheria plants are not true mints. Oil of wintergreen is also manufactured from some species of birch, but these deciduous trees are not called wintergreens. Spiraea plants also contain methyl salicylate in large amounts and are used similarly to wintergreen. Toxicity of Wintergreen 30 mL (about 1 fl oz) of oil of wintergreen is equivalent to 55.7 g of aspirin, or about 171 adult aspirin tablets (US). This conversion illustrates the potency and potential toxicity of oil of wintergreen even in small quantities. Illiteracy may be a common factor in accidental overdoses and ingestions in adults. Treatment is identical to the other salicylates. Early use of hemodialysis in conjunction with maximal supportive measures is encouraged in any significant ingestion of methyl salicylate. Strong warning labels are recommended for household salicylate-containing compounds such as oil of wintergreen.