Wintergreen
Scientific Name(s): Gaultheria procumbens L.
Common Name(s): Boxberry, Canada tea, Checkerberry, Deerberry, Gaultheria oil, Mountain tea, Partridgeberry, Teaberry, Wintergreen
Medically reviewed by Drugs.com. Last updated on Jan 12, 2023.
Clinical Overview
Use
Wintergreen oil has been used as a pesticide, fragrance ingredient, and flavoring agent. Wintergreen oil has also been used as a topical analgesic and rubefacient for the treatment of muscular and rheumatic pain; however, no clinical data support the use of wintergreen oil (alone) for any condition.
Dosing
Dosing recommendations for oral or topical administration of wintergreen oil are not available. Wintergreen oil is 98% methyl salicylate. 1 mL of wintergreen oil is equivalent to 1.4 g of aspirin; therefore, 5 mL of wintergreen oil is equivalent to approximately 7 g of aspirin (which is the equivalent of 21.5 aspirin [325 mg] tablets). Even small doses of oral wintergreen oil may cause toxicity.
Contraindications
Avoid oral or topical application in children. Avoid use in individuals with known hypersensitivity to any components of wintergreen oil; in individuals with known salicylate allergy, bleeding disorders, or GI irritation; and in hypersensitive asthmatics.
Pregnancy/Lactation
Avoid dosages higher than those found in food. Safe use of salicylates (including wintergreen oil) during pregnancy has not been established.
Interactions
Monitor for potentiation of warfarin anticoagulation in patients using methyl salicylate or topical wintergreen oil.
Adverse Reactions
Wintergreen may cause hypersensitivity reactions. Topical administration of methyl salicylate may cause redness and irritation; second- and third-degree burns have been reported rarely with products containing menthol alone or menthol and methyl salicylate.
Toxicology
Wintergreen has generally recognized as safe (GRAS) status when used as a flavoring agent in foods. Dosages higher than those found in food should be avoided. Wintergreen oil is highly concentrated, lipid soluble, and able to pass through the skin, posing a threat of severe, rapid-onset salicylate poisoning. The toxic potential of topical medicaments containing methyl salicylate or wintergreen oil should be fully appreciated. When ingested, highly concentrated liquid methyl salicylate in the form of wintergreen oil can induce vomiting and cause severe, often fatal, poisoning.
Scientific Family
- Ericaceae
Botany
Wintergreen is a perennial evergreen shrub with thin, creeping stems and leathery leaves with toothed, bristly margins. It is a low-growing plant native to eastern North America and usually found in woodland and exposed mountainous areas. Its small, waxy, white or pale pink flowers bloom in late summer, developing a scarlet fruit. The aromatic leaves and fruits are edible.Chevallier 1996, Simon 1984
History
American Indians used wintergreen for treating back pain, rheumatism, fever, headache, and sore throat.Chevallier 1996 The plant and its oil have been used in traditional medicine for their analgesic, carminative, astringent, and topical rubefacient effects. Wintergreen tea has been used to relieve cold symptoms and muscle aches.Dobelis 1986 Wintergreen oil and sweet birch oil have historically been used interchangeably, as both contain more than 90% w/w methyl salicylate.
Wintergreen berries have been used to make pies.Duke 1985 A tea made from the leaves was used as a substitute for Camellia sinensis tea during the Revolutionary War.Chevallier 1996
Chemistry
Wintergreen oil is an extremely potent liquid form of methyl salicylate (98% methyl salicylate w/w).Chyka 2007 It is produced by macerating wintergreen leaves in warm water, followed by steam distillation.Khan 2010 During the process, gaultherin is enzymatically hydrolyzed to methyl salicylate.Simon 1984 The yield of wintergreen oil from the leaves ranges from 0.5% to 0.8%.Khan 2010 Production of wintergreen oil by distillation from the natural product has been largely replaced by synthetic production of methyl salicylate.Bone 2013 Wintergreen oil has a distinct sweet aromatic odor and is either colorless or has a red or yellow tinge.Burdock 2010
Uses and Pharmacology
Salicylates, along with capsaicin, menthol, and camphor, are a counterirritant class of topical analgesics. These compounds produce analgesia by activating and then desensitizing epidermal nociceptors.(Barkin 2013)
Topical wintergreen oil is a counterirritant that offers some analgesic effect because of the structural similarity of methyl salicylate to aspirin. Methyl salicylate formulations may also contain menthol and/or camphor and are available as gels, creams, ointments, and sprays.(Olenak 2012) Typically, these products contain from 10% to 40% methyl salicylate (United States Pharmacopeia) and are used in the treatment of painful muscles or joints.
Methyl salicylate is also used as a pesticide, fragrance ingredient, and flavoring agent. More recently, wintergreen oil has been used as a flavoring agent in tobacco products.(Greene 2017)
Analgesic effects
Research reveals no clinical data regarding the efficacy of wintergreen oil (alone) for any condition. However, the pain relief capabilities of methyl salicylate are better established and a multitude of over-the-counter products are available.(Anderson 2017)
Clinical data
In a randomized, double-blind, parallel-group, placebo-controlled, multicenter study of 208 patients with pain associated with mild to moderate muscle strain, a patch containing methyl salicylate and l-menthol provided significantly greater pain relief after 8 hours compared with the placebo group (P=0.005).(Higashi 2010)
Antiplatelet effects
Clinical data
Topical administration of methyl salicylate results in systemic salicylate exposure.(Morra 1996) In a small randomized, blinded, crossover trial, 9 healthy men received either a single oral dose (162 mg) of aspirin (a mainstay of chronic antiplatelet therapy in patients at risk for acute coronary syndrome) or 5 g of a topical methyl salicylate 30% preparation administered to the anterior thighs. Both treatments decreased platelet aggregation compared with baseline.(Tanen 2008)
Insecticidal effects
Animal and in vitro data
Insecticidal activity of wintergreen oil was demonstrated against Paederus fuscipes in both in vitro and in vivo experiments. P. fuscipes is a major predator of several agricultural pests but can cause dermatitis linearis in humans. The mechanism of action was related to inhibition of acetylcholinesterase in adult insects that was not significantly different from the positive control (chlopyrifos).(Liu 2018)
Dosing
Dosing recommendations for oral or topical administration of wintergreen oil are not available. Wintergreen oil is 98% methyl salicylate. 1 mL of wintergreen oil is equivalent to 1.4 g of aspirin; therefore, 5 mL of wintergreen oil is equivalent to approximately 7 g of aspirin (which is the equivalent of 21.5 aspirin [325 mg] tablets). Even small doses of oral wintergreen oil may cause toxicity.Chyka 2007
Pregnancy / Lactation
Wintergreen has GRAS status when used as food flavoring. Avoid dosages higher than those found in food because safety has not been established.
Interactions
In case reports and case series, topical administration of methyl salicylate has been reported to cause increases in international normalized ratio (INR) (as high as 12.2) when coadministered with warfarin, resulting in bruising, retroperitoneal bleeding, and GI bleeding. Individuals using methyl salicylate or wintergreen oil should be monitored for increased warfarin effects.Chan 2009, Joss 2000, Yip 1990
Adverse Reactions
One case report documents a potential hypersensitivity reaction in a nonsmoking, 21-year-old woman with a history of asthma who complained of wheezing, dry cough, and bronchial pain after using a tartar-control toothpaste flavored with wintergreen oil.McCarthy 1992 Another case report documents the development of laryngeal edema in an individual after accidental ingestion of wintergreen oil.Botma 2001 Because wintergreen oil is absorbed and converted to salicylic acid after both oral and topical administration, it should be used with caution in individuals with nonallergic aspirin sensitivity.Howrie 1985, Morra 1996, Olenak 2012
Wintergreen oil may cause hypersensitivity reactions, with topical administration of methyl salicylate causing redness and irritation.Olenak 2012 Second- and third-degree burns have been reported rarely with topical products containing menthol alone or menthol and methyl salicylate in concentrations greater than 3% and 10%, respectively. Most reported reactions occurred within 24 hours of initial application.FDA 2012
Toxicology
Wintergreen has GRAS status when used as food flavoring. Several regulatory agencies have established an acceptable daily intake of 0.5 mg/kg/day for methyl salicylate.Greene 2017
Wintergreen oil is highly concentrated and lipid soluble; therefore, it poses a threat of severe, rapid-onset salicylate poisoning. The toxic potential of topical medicaments containing methyl salicylate or wintergreen oil should be fully appreciated.Chan 1996 Salicylate toxicity following intentional ingestion of a plant-based insecticide with wintergreen oil as a minor ingredient has been reported in a suicide attempt by a 74-year-old woman.Moss 2020
Typical symptoms of salicylate toxicity (eg, hematemesis, tachypnea, hyperpnea, dyspnea, tinnitus, deafness, lethargy, seizures, unexplained lethargy, confusion) warrant referral to an emergency department for evaluation.Chyka 2007
When ingested, the highly concentrated liquid methyl salicylate, in the form of wintergreen oil, can induce vomiting and cause severe, often fatal, salicylate poisoning.Duke 1985, Howrie 1985 The oil may be particularly toxic to children, who may associate the pleasant odor of wintergreen oil with "candy." Wintergreen oil 1 mL is equivalent to aspirin 1.4 g.Chyka 2007 Ingestion of as little as 4 mL in a child and 6 mL in an adult has been fatal.Chyka 2007, Dreisbach 1987, Tyler 1988 In the United States between 1990 and 2000, there were 3 acute drug ingestion fatalities in children 2 years or younger.Koren 2019
Because of the potential for toxicity, official labeling requirements have been changed for drug products containing more than 5% methyl salicylate.FDA 2015 In these cases, labelling must warn that the product may be dangerous and that it should be kept out of reach of children to prevent accidental poisoning. The American Association of Poison Control Centers recommends emergency department referral for ingestion of more than a lick or taste of wintergreen oil (methyl salicylate 98%) in a child younger than 6 years.Chyka 2007 No deaths have been reported from ingestion of the plant itself.Simon 1984
In the case of overdose, do not induce emesis for ingestions of salicylates or wintergreen oil. If immediately available and no contraindications are present, consider out-of-hospital administration of activated charcoal for acute ingestion of a toxic dose of methyl salicylate.Chyka 2007 Salicylate poisoning is usually treated with activated charcoal and alkaline diuresis or hemodialysis.
Because the essential oil and its components can be absorbed through the skin, salicylate intoxication can occur following topical application of methyl salicylate or wintergreen oil. Due to a structural similarity between methyl salicylate and acetylsalicylic acid (aspirin), a toxic syndrome similar to that seen in salicylism and characterized by tinnitus, nausea, and vomiting has been observed in individuals ingesting wintergreen for prolonged periods of time.Duke 1985
A 40-year-old man became acutely ill within 1 hour after an herbalist applied an herbal skin cream containing an unknown amount of wintergreen oil for the treatment of psoriasis. Salicylate absorption may have been increased by use of an occlusive dressing. The patient developed tinnitus followed by hyperpnea, vomiting, diaphoresis, fever, and CNS disturbance.Bell 2002
Case reports involving accidental methyl salicylate poisoning are common.Seneviratne 2015 A 70-year-old woman seeking relief for chronic knee pain developed fatal clinical manifestations of methyl salicylate poisoning (eg, acid-base disturbance, endocrine abnormalities, fluid and electrolyte imbalances, CNS toxicity) after ingesting topical Koong Yick Hung Fa Oil 60 mL, which contains salicylic acid 56.2 g (the equivalent of 173 regular-strength adult aspirin tablets).Hofman 1998
In a review assessing toxicity from oral exposure to methyl salicylate, dose-response modeling showed changes in the reproductive/development end points after exposure to 500 mg/kg/day of methyl salicylate in male and female mice.Greene 2017
References
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