Wintergreen essential oil (Gaultheria procumbens) was one of my go-to oils when I was struggling with extreme discomfort from a herniated disc years ago. Recently, I became more curious about this amazing smelling oil for two reasons.

(1) Someone asked me about its mechanisms and uses.

(2) I was presented with a question on its safety internally because I had shared that I use one to two drops a day on my toothbrush.

Below, I highlight the role of wintergreen in wellness. I also provide a few safety considerations that shouldn’t prevent you from its use, but as a heads up. As usual, the abstracts are provided for your skimming pleasure and to conform to FDA regulations.

The Many Varieties of Wintergreen

As with any essential oil there are various species within the same botanical family. Wintergreen exhibits similar and different properties dependent on its chemotype (variations in the presence of plant secondary metabolites) and the distillation technique used to extract what is deemed the most therapeutic constituents. For example, this abstract demonstrated that, within the 22 species of Gaultheria examined, there were similarities in constituents (phenols and phenolic acids) as well as variations in derivatives of salicylic acid among them.

Abstract: Twenty-two species of Gaultheria were examined for phenols and phenolic acids obtained by hydrolysis of ethanolic extracts. Most species yielded p-hydroxybenzoic, o-pyrocatechuic, protocatechuic, gentisic, vanillic, p-coumaric, caffeic and ferulic acids. Thirteen species contained derivatives of salicylic acid as well; the glycoside gaultherin was isolated from two of these. The three species of the section Amblyandra yielded catechol as the major phenol in hydrolyzates of ethanolic extracts. Catechol-?-D-glucopyranoside was isolated from one of these. The relationship of these phenolic compounds to one another is discussed. (1)

This is why, beyond assuring if a company uses GC/MS analysis of constituents present and/or uses European standardizations, you will want to verify what other types of testing they use for purity and assessment of quality.

Salicylic Acid vs. Methyl Salicylate

Salicylic acid is a phenolic acid and beta hydroxy acid that is derived from willow bark and metabolized from salicin. It is the active metabolite in aspirin and has been studied to modulate inflammation.

Abstract: For several millennia, the willow tree and salicin have been associated with salicylic acid, the key precursor molecule that has contributed to the discovery of acetylsalicylic acid, traded as aspirin. These molecules have been shown to possess phyto- and chemotherapeutic activities as analgesic drugs. In recent decades, aspirin has become the focus of extensive investigation into antiproliferative and anticancer activities. The historical steps that led to the discovery of aspirin, and its antiproliferative and anticancer potential are highlighted in this review. (2)

Methyl salicylate, the main component of Gaultheria procumbens, is an organic ester. Five ml of methyl salicylate equals approximately 7g of salicylate (21.7 adult aspirin tablets). (3) This makes the essential oil very powerful at small doses (more on this later).

Previously, I discussed the wide use of nonsteroidal anti-inflammatory drugs (NSAIDs) along with some of the most common side effects including increased gastrointestinal issues and cardiovascular complications. For this reason, natural alternatives have been studied.

One such study sought to determine how a derivative found in a species of wintergreen, gaultherin, modulated inflammation without producing the gastric side effects. It was thought that it was due to its slow release of salicylate activity in the small intestine after metabolism by gut microflora and the liver. The researchers concluded that gaultherin not only inhibited abdominal contractions, but had comparable effects in modulating inflammation to a similar dose of aspirin.

Abstract:

One of the major factors limiting the use of non-steroidal anti-inflammatory drugs is gastrointestinal toxicity. Gaultherin, 2-[(6-O-?-d-Xylopyranosyl-?-d-glucopyranosyl)oxy] benzoic acid methyl ester, a natural salicylate derivative extracted from Gaultheria yunnanensis, has been shown to have analgesic and anti-inflammatory effects and lack gastric ulcerogenic effect compared to aspirin in our primary study. The aim of this study was to investigate the mechanism of action of gaultherin, which may rely on its active metabolite, and the mechanism responsible for the non-ulcerogenic property. The results showed that gaultherin (200 mg/kg) significantly inhibited the abdominal contractions in the acetic acid-induced writhing test in mice. The anti-inflammatory effect of gaultherin was demonstrated in the croton oil-induced ear edema model in mice. The results showed that gaultherin and equimolar dose of aspirin produced comparable inhibitory effects. The study of the metabolism characters of gaultherin in mice and rats indicated that gaultherin could be metabolically converted to salicylate, which produced the pharmacological effects, and provided effective concentrations for an extended period. In vitro metabolism experiment showed that gaultherin was metabolized by ?-glycosidase produced by human intestinal bacteria and esterases in intestine, blood and liver successively to release salicylate finally. The study suggested gaultherin did not cause gastric ulcer for the reason that it released salicylate in intestine slowly, not in stomach and it left the cyclooxygenase-1 unaffected, which was the source of cytoprotective prostaglandins in gastric epithelium. (4)

Another study further supported how methyl esters of salicylic acids derivatives may provide an alternative to the synthetic forms of salicylic acid, such as aspirin for those with sensitive bellies:

 Abstract:

The methyl and some other esters of acetylsalicylic and salicylic acids and their derivatives were found to have much lower gastric ulcerogenic activity (when assayed in the stress-sensitized rat) compared with their corresponding acids. There was little or no loss in therapeutic potencies of these salicylate esters as determined by assessment of anti-inflammatory activity (against the carrageenan-induced oedema) and antipyretic activity (against yeast-induced fever in rats. The methyl ester of acetylsalicylic acid (=AME) was almost devoid of gastric irritancy/ulcerogenicity (as observed with acetylsalicylic acid) when given orally to pigs for 10 days. AME had appreciable anti-inflammatory activity in the adjuvant-arthritis model and at high doses (200 mg/kg t.i.d.) was without the lethal effects seen with acetylsalicylic acid. Moreover, no toxic effects were seen after long-term administration of 100–1000 mg/kg/day AME for 3–4 months.

The results provide further evidence for the hypothesis that the carboxylic acid moiety of salicylates is a major factor in the gastric ulcerogenic activity of these drugs. The methyl esters of these salicylates may be considered as models for the development of pro-drugs and in some cases may be therapeutic alternatives to acetylsalicylic acid or salicylate. (5)

Due to the its role in modulating inflammation, topical applications of salicylic acid have also been studied.

Abstract: The acute contra-inflammatory effects of salicylic acid, three standard dermatocorticoids and four contact antiphlogistics have been investigated by means of a UV dermatitis inhibition test in the guinea pig. The substances tested had a distinct inhibitory effect on the development of erythema and can be ranked in the following ascending order of activity (percent of maximum possible score): bufexamac = 36%, salicylic acid = 37%, hydrocortisone = 44%, acetylsalicylic acid = 48%, flumethasone pivalate = 51%, fluocinolone acetonide = 51%, phenylbutazone = 56%, and indomethacin = 58%. (6)

Another study examined the effect of a topical application for modulating discomfort using a combination of capsaicin and methyl salicylate on cats. The study demonstrated that this modulated pain perception independent of central pathways, as demonstrated by pressor responses.

PURPOSE: Pressor responses are reflexly evoked by the activation of groups III and IV muscle afferents, which are also known to mediate nociceptive responses. In this experiment, the effects of analgesic balm (AB) application on these responses were investigated without the interference of other types of anesthesia or effects from the higher brain.

METHODS: Heart rate (HR), blood pressure, and end-tidal CO(2) were monitored in midcollicularly decerebrated cats. Static contractions (30 s) of hindlimb muscles were evoked by electric stimulation of L7 and S1 ventral roots. After control runs, a commercial AB (1% capsaicin, 12.5% methyl salicylate) was applied to the skin surface over the contracting muscles. Muscle contractions were evoked every 10 min, alternating between the two hindlimbs.

RESULTS: Changes in mean arterial pressure (MAP) evoked by static ipsilateral muscular contraction were significantly attenuated 20 min and 40 min after AB application. The decreases in the pressor response were significant at both the initial and the last parts of the stimulus intervention after 20 min of AB application. There were no significant changes in the response to contraction of the hindlimb contralateral to the AB application. Application of AB to the contralateral leg did not add to the ipsilateral effects.

CONCLUSIONS: AB application to the skin surface over contracting muscles significantly decreased autonomic responses to static muscular contraction. This effect was independent of higher cortical processing and strongly suggests that application of methyl salicylate and capsaicin on the skin has analgesic effects on signals from receptors located in muscle. (7)

Dental Health

Wintergreen’s ability to act as an antioxidant to protect against damaging effects of bacteria in the mouth was studied in vitro. The authors concluded that their results with wintergreen merit further investigation in future studies in those with periodontal disease.

Abstract:

OBJECTIVES: Several forms of periodontal diseases (PD) are often associated with activated phagocytosing leukocytes and contemporary free radical production. Host antioxidant defenses could benefit from mouthrinses used as adjuncts to counteract plaque-associated bacteria. The aim of the present study was to determine possible antioxidant activity (AA) of a number of antiseptic mouthrinses and of their stated active principles (AP), regardless of their efficacy as antimicrobial agents.

MATERIAL AND METHODS: The antioxidant activities of 11 mouthrinses and their active principles were tested with a specific spectrophotometric method. Comet assay was used to test whether pure chemical antioxidant activity actually corresponded to prevention of in vitro DNA fragmentation.

RESULTS: Methylsalicylate-containing mouthrinses were the most effective. Several compounds, and some vehicles, behaved as antioxidants. Fibroblast DNA fragmentation was limited by preincubation with methylsalicylate-containing mouthrinse but was unaffected by treatment with chlorexidine.

CONCLUSION: The results described herein indicate that several mouthrinses possess AA; such a property could be ascribed to either AP or vehicles or both. All the data were obtained in systems in vitro and the demonstration of in vivo AA is necessary. These findings could be useful in the treatment of some forms of PD and should be considered when arranging new mouthrinse formulations. (8)

Microbe Inhibition in Vitro

This pure oil has also been studied in one in vitro test and shown to inhibit growth of various microorganisms and microbe biofilms:

ABSTRACT The aim of this study was to examine chemical composition and biological activity of Gaultheria procumbens L. essential oil (EO) against food spoilage and oral microorganisms. The components of EO were identified by GC–MS. Antimicrobial activity was determined against food spoilage (five bacteria and six fungal species) and oral microorganisms (eight bacteria and thirty two fungal species) by microdilution and microplate biofilm assay, antioxidant activity was tested using the persistent free radical 2,2-diphenyl-1-picryl hydrazyl (DPPH), while antiradical activity was examined by fluorescence spectroscopy and electron paramagnetic resonance spectroscopy (EPR). GC–MS.analysis showed that methyl salicylate (96.90%) was the main component of the oil. Essential oil inhibited the growth of all microorganisms tested, i.e. food and oral bacteria and fungi, respectively (MIC 0.18–3.00 mg/ml and MBC 1.25–4.00 mg/ml; MIC 0.73–5.00 mg/ml and MFC 2.92–26.67 mg/ml); The oil effectively inhibited the biofilm formation of oral Streptococcus mutans and Candida albicans as well (MIC 25.00 MBC 50.00 mg/ml; MIC 12.50, MFC 50.00 mg/ml). In addition, oil exhibited a dose-dependent DPPH-radical-scavenging activity with IC 50 value of 30.61 mg/ml. The specific fluorescence probe 2-[6-(4 -amino)phenoxy-3H-xanten-3-on-9-yl] benzoic acid (APF) and the the spin trap 5-(Diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), capable for simultaneous detection of different free radical specie were used in antiradical activity of the oil measurements. Oil showed a moderate antiradical activity, reducing quantity of produced hydroxyl radicals to about 20% of initial value. This study succeeds in creating directly comparable and quantitative data for the oil unsufficiently examined so far. (9)

Safety of Wintergreen

When used properly as directed, essential oils have a good safety profile. Wintergreen can provide many benefits; however, it is very powerful and should not be used in children and only as directed with adults. This is due to several reports of children ingesting the oil. Most reports are with children drinking 5ml or more (1/3^rd of a typical bottle). For this reason, most companies use a child safety cap on the oil. (3, 10-13)

Another caution with such a powerful oil is that wintergreen may interact with warfarin and should not be used in conjunction with it or other blood thinners. It is also to be used cautiously with those who are pregnant and are epileptic. (14)

Disclaimer: This information is applicable ONLY for therapeutic, Grade A essential oils. This information DOES NOT apply to essential oils that have not been AFNOR and ISO standardized. There is no quality control in the United States and oils labeled as “100% pure” need only contain 5% of the actual oil. The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin. This information is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness. Please see the original study for the source. This is not specific for any essential oils company or brand.

References:

(1) Towers, G. H. N., Aida Tse, and W. S. G. Maass. “Phenolic acids and phenolic glycosides of Gaultheria species.” Phytochemistry. 5.4 (1966): 677-681.Mahdi, J. G., Mahdi, A. J.,

(2) Mahdi, A. J. and Bowen, I. D. The historical analysis of aspirin discovery, its relation to the willow tree and antiproliferative and anticancer potential. Cell Proliferation. 2006; 39: 147–155. doi: 10.1111/j.1365-2184.2006.00377.x

(3) Laryngeal oedema caused by accidental ingestion of Oil of Wintergreen. Int J Pediatr Otorhinolaryngol. 2001 May 11;58(3):229-32.

(4) Zhang, Bin, et al. “Gaultherin, a natural salicylate derivative from Gaultheria yunnanensis: Towards a better non-steroidal anti-inflammatory drug.” European journal of pharmacology. 530.1 (2006): 166-171.

(5) Rainsford, K. D., and M. W. Whitehouse. Anti-inflammatory/anti-pyretic salicylic acid esters with low gastric ulcerogenic activity. Agents and actions 10.5 (1980): 451-456.

(6) Weirich, E. G., J. K. Longauer, and A. H. Kirkwood. “Dermatopharmacology of salicylic acid. III. Topical contra-inflammatory effect of salicylic acid and other drugs in animal experiments.” Dermatologica 152.2 (1975): 87-99.

(7) Effects of topical analgesics on the pressor response evoked by muscle afferents. Med Sci Sports Exerc. 2002 Sep;34(9):1440-5.

(8) In vitro antioxidant activities of mouthrinses and their components. J Clin Periodontol. 2002 May;29(5):462-7. PMID:12060430

(9) Nikoli?, Miloš, et al. Chemical composition and biological activity Gaultheria procumbens essential oil. Industrial Crops and Products. 2013; 49: 561-567.

(10) Salicylate poisoning: an evidence-based consensus guideline for out-of-hospital management. Clin Toxicol (Phila). 2007;45(2):95-131

(11) Are one or two dangerous? Methyl salicylate exposure in toddlers. J Emerg Med. 2007 Jan;32(1):63-9.

(12) Chin RL, Olson KR, Dempsey D. Salicylate Toxicity from Ingestion and Continued Dermal Absorption. The California Journal of Emergency Medicine. 2007;8(1):23-25.

(13) Shirreff WT, Pearlman LN. OIL OF WINTERGREEN POISONING?: (Report of Two Additional Fatal Cases). Canadian Medical Association Journal 1940;43(3):264-268

(14) Potentiation of warfarin anticoagulation associated with topical methyl salicylate. Ann Pharmacother. 2000 Jun;34(6):729-33.

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